Glossary: A


the addition of an acetyl group (-COCH3) group to a molecule.
the absence of hydrochloric acid in gastric juice.
having a pH of less than 7.
Acne vulgaris
a condition of the skin characterized by the presence of comedones.
Acrodermatitis enteropathica
a rare, inherited disorder of impaired zinc absorption.
Actinic lentigines
hyperpigmented patches that occur in sun-exposed skin; also known as liver spots or age spots.
having a short and relatively severe course.
Acute-phase reactant protein
also called acute-phase protein; plasma protein that is synthesized by the liver during acute inflammation. Examples include C-reactive protein (CRP), fibrinogen, serum amyloid A protein, and von Willebrand factor.
Action potential
the electrochemical signal transmitted in the cell membrane of a neuron or muscle cell. Also called nerve impulse.
Adipose tissue
specialized connective tissue that functions to store body fat as triglycerides.
Adjunct therapy
a treatment or therapy used in addition to another, not alone.
Adrenal glands
a pair of small glands, located above the kidneys, consisting of an outer cortex and inner medulla. The adrenal cortex secretes cortisone-related hormones and the adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline).
the nonsugar component of a glycoside. Cleavage of the glycosidic bond of a glycoside results in the formation of a sugar and an aglycone.
adequate intake. Established by the Food and Nutrition Board of the US Institute of Medicine, the AI is a recommended intake value based on observed or experimentally determined estimates of nutrient intake by a group of healthy people that are assumed to be adequate. An AI is established when an RDA cannot be determined.
acquired immune deficiency syndrome. AIDS is caused by the HIV (Human Immunodeficiency Virus) virus, which attacks the immune system, leaving the infected individual vulnerable to opportunistic infections.
basic; having a pH of more than 7.
a plant-derived compound that is biologically active, contains a nitrogen in a heterocyclic ring, is alkaline, has a complex structure, and is of limited distribution in the plant kingdom.
one of a set of alternative forms of a gene. Diploid cells possess two homologous chromosomes (one derived from each parent) and therefore two copies of each gene. In a diploid cell, a gene will have two alleles, each occupying the same position on homologous chromosomes.
loss of hair.
Alzheimer's disease
the most common cause of dementia in older adults. Alzheimer’s disease is characterized by the formation of amyloid plaque in the brain and nerve cell degeneration. Symptoms include memory loss and confusion, which worsen over time.
Amino acid
an organic molecule that contains an amino group (-NH2) and a carboxyl group (-COOH); amino acids are as the building blocks of proteins.
adenosine monophosphate. A important compound in energy metabolism. Addition of two phosphates to AMP forms ATP.
a chemical compound having both hydrophilic (water-loving, polar) and lipophilic (fat-loving, nonpolar) properties.
Amyloid plaque
aggregates of a peptide called amyloid-β, which accumulate and form deposits in the brain in Alzheimer’s disease.
Amyotrophic lateral sclerosis (ALS)
a rapidly progressive and fatal neurological disease caused by degeneration of motor neurons that control voluntary muscle movement. Also known as Lou Gehrig’s disease.
the synthesis of large complex molecules from simple molecules.
refers to the absence of oxygen or the absence of a need for oxygen.
a chemical compound that is structurally similar to another but differs slightly in composition (e.g., the replacement of one functional group by another).
a rapidly developing and severe systemic allergic reaction. Symptoms may include swelling of the tongue, throat, and trachea, which can result in difficulty breathing, shock and loss of consciousness. If not treated rapidly, anaphylaxis can be fatal.
the condition of having less than the normal number of red blood cells or hemoglobin in the blood, resulting in diminished oxygen transport. Anemia has many cause, including iron, vitamin B12, or folate deficiency; bleeding; abnormal hemoglobin formation (e.g., sickle cell anemia); rupture of red blood cells (hemolytic anemia); and bone marrow diseases.
a birth defect, known as a neural tube defect, resulting from failure of the upper end of the neural tube to close during embryonic development. Anencephaly is a devastating and sometimes fatal birth defect resulting in the absence of most or all of the cerebral hemispheres.
Angina pectoris
pain generally experienced in the chest, but sometimes radiating to the arms or jaw, due to a lack of oxygen supply to the heart muscle.
the development of new blood vessels.
Angiography (coronary)
imaging of the coronary arteries used to identify the location and severity of any obstructions. Coronary angiography typically involves the administration of a contrast medium and imaging of the coronary arteries using an X-ray based technique.
a negatively charged ion.
the absence of the external ear.
a substance that counteracts or nullifies the biological effects of another, such as a compound that binds to a receptor but does not elicit a biological response.
before birth; also called prenatal.
relating to the measurement of the human body.
a specialized protein produced by white blood cells (lymphocytes) that recognizes and binds to foreign proteins or pathogens in order to neutralize them or mark them for destruction.
a class of compounds that inhibit blood clotting.
a class of medication used to prevent seizures.
a substance that is capable of eliciting an immune response.
a chemical that blocks the effect of histamine in a susceptible tissues.  Histamine is released by immune cells during an allergic reaction and also during infection with viruses that cause the common cold.  The interaction of histamine with the mucus membranes of the eyes and nose results in "watery eyes" and the "runny nose" often accompanying allergies and colds.  Antihistamines can help alleviate such symptoms.
capable of killing or inhibiting the growth of microorganisms, such as bacteria.
any substance that prevents or reduces damage caused by reactive oxygen species (ROS) or reactive nitrogen species (RNS).
Antiresorptive agent
a medication or hormone that inhibits bone resorption.
an agent that decreases anxiety.
Apgar score
a scoring system used to assess the physical condition of a newborn immediately after birth. Criteria evaluated include respiratory effort, heart rate, skin coloration, muscle tone, and response to stimulation.
gene-directed cell death or programmed cell death that occurs when age, condition, or state of cell health dictates. Cells that die by apoptosis do not usually elicit the inflammatory responses that are associated with necrosis. Cancer cells are resistant to apoptosis.
referring to water or a solution containing water.
an abnormal heart rhythm. The heart rhythm may be too fast (tachycardia), too slow (bradycardia) or irregular. Some arrhythmias, such as ventricular fibrillation, may lead to cardiac arrest if not treated promptly.
a lack of oxygen or excess carbon dioxide in the body that causes unconsciousness.
a chronic inflammatory disease of the airways, characterized by recurrent episodes of reversible airflow obstruction.
a type of glial cell in the central nervous system.
a lack of coordination or unsteadiness usually related to a disturbance in the cerebellum, a part of the brain that regulates coordination and equilibrium.
capable of producing atherosclerosis.
an inflammatory disease resulting in the accumulation of cholesterol-laden plaque in artery walls. Rupture of atherosclerotic plaque results in clot formation, which may result in myocardial infarction or ischemic stroke.
adenosine triphosphate. An important compound for the storage of energy in cells, as well as the synthesis of nucleic acids.
(singular: atrium) two upper chambers of the heart that receive blood from the veins and contract to force that blood into the ventricles.
Atrial fibrillation
a cardiac arrhythmia, characterized by rapid, uncoordinated beating of the atria, which results in ineffective atrial contractions. Atrial fibrillation is known as a supraventricular arrhythmia because it originates above the ventricles.
Atrophic gastritis
a chronic inflammation of the lining of the stomach, which ultimately results in the loss of glands in the stomach (atrophy) and decreased stomach acid production.
a decrease in size or wasting away of a body part or tissue.
a reduction in number.
Autoimmune disease
a condition in which the body's immune system reacts against its own tissues.
the phosphorylation by a protein of one or more of its own amino acid residues. Autophosphorylation does not necessarily occur on the same polypeptide chain as the catalytic site. In a dimer, one subunit may phosphorylate the other.
refers to a trait or gene that is not located on the X or Y chromosome (not sex-linked).
long extension of a neuron that transmits nerve impulses away from the cell body toward other neurons or muscle cells.

Glossary B:

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single-celled organisms that can exist independently, symbiotically (in cooperation with another organism) or parasitically (dependent upon another organism, sometimes to the detriment of the other organism). Examples of bacteria include acidophilus (found in yogurt); streptococcus the cause of strep throat; and E. coli (a normal intestinal bacteria, as well as a disease-causing agent).
Balance study
a nutritional balance study involves the measurement of the intake of a specific nutrient as well as the elimination of that nutrient in urine, feces, sweat, etc. If intake is greater than loss of a particular nutrient the individual is said to be in "positive balance." If intake is less than loss, an individual is said to be in "negative balance" for the nutrient of interest.
the branch of medicine that relates to the treatment of obesity.
not malignant.
Benign prostatic hyperplasia
the term used to describe a noncancerous enlargement of the prostate.
any systematic error in an epidemiological study that results in an incorrect estimate of the association between an exposure and disease risk.
a yellow, green fluid made in the liver and stored in the gallbladder. Bile may then pass through the common bile duct into the small intestine where some of its components aid in the digestion of fat.
Bile acids
components of bile, which are formed by the metabolism of cholesterol, and aid in the digestion of fats.
the fraction of an administered compound that reaches the systemic circulation and is transported to site of action (target tissue).
a physical, functional, or biochemical indicator of a physiological or disease process.
Biotransformation enzymes (phase I and phase II)
enzymes involved in the metabolism and elimination of a variety of exogenous (drugs, toxins and carcinogens) and endogenous compounds (steroid hormones). In general, phase I biotransformation enzymes, including those of the cytochrome P450 family, catalyze reactions that increase the reactivity of fat-soluble compounds and prepare them for reactions catalyzed by phase II biotransformation enzymes. Reactions catalyzed by phase II enzymes generally increase water solubility and promote the elimination of these compounds.
Bipolar disorder
a mood disorder previously called “manic-depressive illness.” Bipolar disorder is characterized by severe alterations in mood. During “manic” episodes, a person may experience extreme elevation in energy level and mood (euphoria) or extreme agitation and irritability. Episodes of depressed mood are also common in bipolar disorder.
Body mass index (BMI)
body weight in kilograms divided by height in meters squared. In adults, BMI is a measure of body fat: underweight, <18.5; normal weight, 18.5-24.9; overweight, 25-29.9; obese, ≥30. Calculate your BMI.
Bone mineral density (BMD)
the amount of mineral in a given area of bone. BMD is positively associated with bone strength and resistance to fracture, and measurements of BMD are used to diagnose osteoporosis.
Bone remodeling
the continuous turnover process of bone that includes bone resorption and bone formation. An imbalance in the regulation of the two contrasting events of bone remodeling (bone resorption and bone formation) increases the fragility of bone and may lead to osteoporosis.
a rumbling sound caused by gas movement in the intestines; sometimes called "stomach rumble."
Branched-chain amino acids
the essential amino acids: leucine, isoleucine, and valine.
Bronchitis, chronic
long-standing inflammation of the airways, characterized by excess production of sputum, leading to a chronic cough and obstruction of air flow. Cigarette smoking is the most common cause of chronic bronchitis.
a chemical used to maintain the pH of a system by absorbing hydrogen ions (which would make it more acidic) or absorbing hydroxyl ions (which would make it more alkaline).

Glossary: C

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C-reactive protein (CRP)
a protein that is produced in the liver in response to inflammation. CRP is a biomarker of inflammation that is strongly associated with the risk of cardiovascular events, such as myocardial infarction and stroke.
the process of deposition of calcium salts. In the formation of bone this is a normal condition. In other organs, this could be an abnormal condition; for example, calcification of the aortic valve causes narrowing of the passage (aortic stenosis).
refers to abnormal cells, which have a tendency to grow uncontrollably and metastasize or spread to other areas of the body. Cancer can involve any tissue of the body and can have different forms in one tissue. Cancer is a group of more than 100 different diseases.
considered a macronutrient because carbohydrates provide a significant source of calories (energy) in the diet. Chemically, carbohydrates are neutral compounds composed of carbon, hydrogen and oxygen. Carbohydrates come in simple forms known as sugars and complex forms, such as starches and fiber.
an enzyme that catalyzes carboxylation reactions.
the introduction of a carboxyl group (-COOH) or carbon dioxide into a compound.
a cancer-causing agent; adjective: carcinogenic.
the formation of cancer cells from normal cells.
Carcinoid syndrome
the pattern of symptoms exhibited by individuals with carcinoid tumors.  Carcinoid tumors secrete excessive amounts of the neurotransmitter, serotonin. Symptoms may include flushing, diarrhea, and sometimes wheezing.
Cardiac output
volume of blood pumped by the heart in a specified time period.
literally, disease of the heart muscle that often leads to abnormal function.
referring to the heart and blood vessels.
Cardiovascular disease
literally, diseases affecting the heart and blood vessels. The term has come to encompass a number of conditions that result from atherosclerosis, including myocardial infarction (heart attack), congestive heart failure, and stroke.
a compound that is required to transport long-chain fatty acids across the inner membrane of the mitochondria, in the form of acyl-carnitine, where they can be metabolized for energy.
Carotid arteries
the left and right common carotid arteries are the principal blood vessels that supply oxygenated blood to the head and neck. Each has two main branches, the external and internal carotid artery.
a soft, elastic tissue that composes most of the skeleton of vertebrate embryos and except for a small number of structures is replaced by bone during ossification in the higher vertebrates. Cartilage cushions joints, connects muscles with bones, and makes up other parts of the body, such as the larynx (voice box) and the outside portion of the ears. 
Case-control study
a study in which exposures of people who have been diagnosed with a disease (cases) are compared to those of people without the disease (controls). The results of case-control studies are more likely to be distorted by bias in the selection of cases and controls (selection bias) and dietary recall (recall bias) than prospective cohort studies.
Case report
a report that decribes an individual case of a disease or medical condition. This type of research cannot indicate causality but may indicate areas for further research.
the breakdown of complex molecules into smaller ones, accompanied by the release of energy.
to increase the speed of a chemical reaction without being changed in the overall reaction process. See enzyme.
clouding of the lens of the eye. As cataracts progress, they can impair vision.
a substance with a specific chemical structure (a benzene ring with two adjacent hydroxyl groups and a side chain of ethylamine) that functions as a hormone or neurotransmitter. Examples include epinephrine, norepinephrine, and dopamine.
a positively charged ion.
Celiac disease
also known as celiac sprue, celiac disease is an inherited disease in which the intestinal lining is inflamed in response to the ingestion of a protein known as gluten. Treatment of celiac disease involves the avoidance of gluten, which is present in many grains, including wheat, rye, oats, and barley. Inflammation and atrophy of the lining of the small intestine leads to impaired nutrient absorption.
Cell adhesion molecule
a molecule on the outside surface of cells that binds to other cells or to the extracellular matrix (material surrounding cells). Cell adhesion molecules influence many important functions, including the entry of immune cells into the arterial wall.
Cell cycle
the orderly sequence of stages that a cell passes through between one cell division (mitosis) and the next. The cell cycle can be divided into four stages: the M (mitosis) phase, in which nuclear and cytoplasmic division occurs; the G1 phase or interphase; the S (synthesis) phase, in which DNA replication occurs; and the G2 phase, a quiescent period prior to the next M phase.
Cell membrane
also called a plasma membrane; the barrier that separates the contents of a cell from its outside environment and controls what moves in and out of the cell. A mammalian cell membrane consists of a phospholipid bilayer with embedded proteins and cholesterol.
Cell signaling
communication among individual cells so as to coordinate their behavior to benefit the organism as a whole. Cell-signaling systems elucidated in animal cells include cell-surface and intracellular receptor proteins, GTP-binding proteins, as well as protein kinases and protein phosphatases (enzymes that phosphorylate and dephosphorylate proteins).
Central nervous system (CNS)
the brain, spinal cord, and spinal nerves.
a specialized type of lipid comprised of a sphingosine backbone with fatty acid side chains. Ceramides function as signaling molecules and are critical structural components in cell membranes.
relating to the brain.
Cerebrospinal fluid
the fluid that bathes the brain and spinal cord.
Cerebrovascular disease
disease involving the blood vessels supplying the brain, including cerebrovascular accident (CVA), also known as a stroke.
the upper part of the brain that is involved in conscious mental functions.
a ferroxidase enzyme that has the capacity to oxidize ferrous iron (Fe2+) to ferric iron (Fe3+), which can be loaded onto the iron-transport protein, transferrin.
Cervical intraepithelial neoplasia (CIN)
a term used to describe abnormal growth of cells on the surface of the uterine cervix. CIN1 is also known as low-grade squamous intraepithelial lesion (LSIL). CIN2 and CIN3 are also known as high-grade squamous intraepithelial lesions (HSIL). Although these abnormal cells are not cancerous, they may progress to cervical cancer.
the combination of a metal with an organic molecule to form a ring-like structure known as a chelate. Chelation of a metal may inhibit or enhance its bioavailability
movement of a cell or organism toward or away from a chemical stimulus.
literally, treatment with drugs. Commonly used to describe the systemic use of drugs to kill cancer cells, as a form of cancer treatment.
removal of the gallbladder.
Cholestatic liver disease
liver disease resulting in the cessation of bile excretion. Cholestasis may occur in the liver, gallbladder, or bile duct (duct connecting the gall bladder to the small intestine).
a compound that is an integral structural component of cell membranes and a precursor in the synthesis of steroid hormones. Dietary cholesterol is obtained from animal sources, but cholesterol is also synthesized by the liver. Cholesterol is carried in the blood by lipoproteins. In atherosclerosis, cholesterol accumulates in plaques on the walls of some arteries.
resembling acetylcholine in action, a cholinergic drug for example. Cholinergic nerve fibers liberate or are activated by the neurotransmitter, acetylcholine.
Chorionic villus sampling (CVS)
a procedure for obtaining a small sample of  tissue from the placenta (chorionic villi) for the purpose of prenatal diagnosis of genetic disorders. CVS can be performed between 9 to 12 weeks of pregnancy.
complex of DNA, RNA, and proteins that comprise chromosomes.
a structure in the nucleus of a cell that contains genes. Chromosomes are composed of DNA and associated proteins. Normal human cells contain 46 chromosomes (22 pairs of autosomes and 2 sex chromosomes).
Chronic disease
an illness lasting a long time. By definition of the US Center for Health Statistics, a chronic disease is a disease lasting three months or more.
Chronic obstructive pulmonary disease (COPD)
a term that includes emphysema and chronic bronchitis, two chronic lung diseases that are characterized by airway obstruction.
triglyceride-rich lipoproteins that deliver dietary triglycerides from the intestine to the tissues immediately after a meal. Chylomicrons release their triglycerides to tissue through the activity of lipoprotein lipase enzymes in tissue capillary beds. When they are depleted of most of their triglycerides, chylomicron remnants are taken up by the liver, where the lipids and cholesterol that remain are excreted in bile or incorporated into other lipoproteins.
the mass of partially digested food that exits the stomach and enters the duodenum of the small intestine.
a condition characterized by irreversible scarring of the liver, leading to abnormal liver function. Cirrhosis has a number of different causes, including chronic alcohol use and viral hepatitis B and C.
Citric acid cycle
the metabolic pathway in the mitochondria that oxidizes acetyl compounds form food to carbon dioxide and water. Also referred to as the Krebs cycle and the tricarboxylic acid (TCA) cycle.
Clinical trial
an intervention trial generally used to evaluate the efficacy and/or safety of a treatment or intervention in human participants.
an exact copy of a DNA segment; produced by recombinant DNA technology.
the process involved in blood clot formation.
a molecule that binds to an enzyme and is essential for its activity but is not permanently altered by the reaction. Many coenzymes are derived from vitamins.
a compound that is essential for the activity of an enzyme.
mental process of thought; includes brain functions like attention, memory, planning, developing strategies, and problem solving.
referring to the processes of cognition.
a group of people who are followed over time as part of an epidemiological study.
Cohort study
a study that follows a large group of people over a long period of time, often 10 years or more. In cohort studies, dietary information is gathered before disease occurs, rather than relying on recall after disease develops.
a fibrous protein that is the basis for the structure of skin, tendon, bone, cartilage and all other connective tissue.
Collagenous matrix (of bone)
the organic (nonmineral) structural element of bone. Collagen is a fibrous protein that provides the organic matrix upon which bone mineralize crystallizes.
the portion of the large intestine that extends from the end of the small intestine to the rectum. The colon removes water from digested food after it has passed through the small intestine and stores the remaining stool until it can be evacuated.
Colorectal adenoma
a polyp or growth in the lining of the colon or rectum. Although they are not cancerous, colorectal adenomas may develop into colorectal cancer over time.
Colorectal cancer
cancer of the colon (large intestine) or rectum.
the surgical construction of an artificial anus by connecting the colon to an opening in the abdominal wall.
a pilosebaceous unit blocked with sebum and inflammatory cells.
system of serum proteins that function to help destroy invading microorganisms.
accompanying. "Concomitant intake" refers to the intake of two compounds at the same time.
Conditionally essential nutrient
although not strictly considered a nutrient due to endogenous synthesis, certain conditions (e.g., stress, aging) may result in the demand exceeding the body's capacity for synthesis, rendering a conditionally essential nutrient.
Confidence interval (CI)
a statistical measure of certainty. A CI defines the range within which we can be certain that a result is not due to chance alone.
an extraneous factor in an observational study that distorts or biases an association between an exposure and the measured outcome. Confounders are associated with the exposure and outcome of interest, but they are not in the causal pathway.
Congenital anomaly
a birth defect, a condition present at birth.
Congenital hypothyroidism
deficiency of thyroid gland activity in newborn infants.
Congenital malformation
birth defects.
Congestive heart failure (CHF)
a condition, in which the heart loses the ability to pump blood efficiently enough to meet the demands of the body. Symptoms may include edema (swelling), shortness of breath, weakness and exercise intolerance.
a compound formed through joining (conjugation) of at least two chemical compounds.
the formation of a water-soluble derivative of a chemical by its combination with another compound, such as glutathione, glucuronate, or sulfate.
the transparent covering of the front of the eye that transmits and focuses light into the eye.
a metabolically inactive, flattened cell of the stratum corneum. Corneocytes are formed from keratinocytes in a process termed cornification. Corneocytes are metabolically inactive and will eventually be cast off from the body when new corneocytes are generated underneath them.
the process by which a keratinocyte becomes a corneocyte in the outer, visible layer of the epidermis. This is marked by a loss of intracellular organelles, the production of specialized proteins and lipids, and the generation of a thick protein envelope just inside the cell membrane. Corneocytes are metabolically inactive and will eventually be cast off from the body when new corneocytes are generated underneath them.
Coronary angioplasty
a procedure used to open an occluded coronary artery. A flexible hollow catheter is inserted into a large blood vessel in the groin and advanced to the heart. At the site of the occlusion, the balloon tip of the catheter is inflated and the occluded coronary artery is dilated. Coronary angioplasty is also known as percutaneous transluminal coronary angioplasty or PTCA.
Coronary artery
one of the vessels that supply oxygenated blood to the heart muscle itself. They are called coronary arteries because they encircle the heart in the form of a crown.
Coronary artery bypass graft (CABG)
a surgical procedure used to create new routes around obstructions in coronary arteries and restore adequate blood flow to the heart muscle.
Coronary heart disease (CHD)
sometimes called coronary artery disease or coronary disease, coronary heart disease is the result of atherosclerosis of the coronary arteries. Atherosclerosis may result in narrowing or blockage of the coronary arteries and is the underlying cause of myocardial infarction (heart attack).
Cortical bone
also known as compact bone, the type of bone that forms the outer surface of all bones. The small bones of the wrists, hands, and feet are entirely cortical bone.
any of the steroid hormones made by the cortex (outer layer) of the adrenal gland. Cortisol is a corticosteroid. A number of medications are analogs of natural corticosteroid hormones.
Covalent bond
a chemical bond in which electrons are shared between atoms.
abnormal skull shape due to the fibrous sutures of the skull having turned into bone prematurely.
Creatine phosphate
a high-energy compound found in muscle cells, which is used to convert ADP into ATP by donating phosphate molecules to the ADP. ATP is the molecule that is converted into ADP with a release of energy that the body then uses.
a condition that can result from a severe form of congenital hypothyroidism. Cretinism occurs in two forms, although there is considerable overlap. The neurologic form is characterized by mental and physical retardation and deafness. It is the result of maternal iodine deficiency that affects the fetus before its own thyroid is functional. The myxedematous or hypothyroid form is characterized by short stature and mental retardation. In addition to iodine deficiency, the hypothyroid form has been associated with selenium deficiency and the presence of goitrogens in the diet that interfere with thyroid hormone production.
Crohn's disease
an inflammatory bowel disease that usually affects the lower part of the small intestine or upper part of the colon but may affect any part of the gastrointestinal tract.
Cross-over trial
a clinical trial where at least two interventions or treatments are applied to the same individuals after an appropriate wash-out period. One of the treatments is often a placebo. In a randomized cross-over design, interventions are applied in a randomized order to ensure that the order of treatments did not contribute to the outcome.
Cross-sectional study
a study of a group of people at one point in time to determine whether an exposure is associated with the occurrence of a disease. Because the disease outcome and the exposure (e.g., nutrient intake) are measured at the same time, a cross-sectional study provides a “snapshot” view of their relationship. Cross-sectional studies cannot provide information about causality.
related to or affecting the skin.
Cystic fibrosis (CF)
a hereditary disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTCR) gene. Cystic fibrosis is characterized by the production of abnormal secretions, leading to the accumulation of mucus in the lungs, pancreas, and intestine. This build-up of mucus causes difficulty breathing and recurrent lung infections, as well as problems with nutrient absorption due to problems in the pancreas and intestines.
Cytochrome P450
a family of phase I biotransformation enzymes that play an important role in the metabolism and elimination of drugs, toxins, carcinogens, and endogenous compounds, such as steroid hormones.
a protein made by cells that affects the behavior of other cells. Cytokines act on specific cytokine receptors in the cells they affect.
the contents of a cell, excluding the nucleus.
the water-soluble contents of a cell's cytoplasm, excluding the organelles.

Glossary: D

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De novo synthesis
the formation of an essential molecule from simple precursor molecules.
the removal of necrotic or infected tissue or foreign material from a wound.
a chemical reaction involving the removal of a carboxyl (-COOH) group from a compound.
significant impairment of intellectual abilities, such as attention, orientation, memory, judgment or language. By definition, dementia is not due to major depression or psychosis. Alzheimer’s disease is the most common cause of dementia in older adults.
loss of the myelin sheath that surrounds a nerve fiber.
a branched extension of a neuron that receives signals from other neurons.
Dendritic cell
an immune cell that functions in antigen presentation and activation of T lymphocytes. Dendritic cells have a branched morphology that resembles dendrites of a neuron.
Dental caries
cavities or holes in the outer two layers of a tooth—the enamel and the dentin. Dental caries are caused by bacteria, which metabolize carbohydrates (sugars) to form organic acids that dissolve tooth enamel.
Depletion-repletion study
a nutritional study designed to determine the requirement for a specific nutrient. Generally, subjects are placed on a diet designed to deplete them of a specific nutrient over time. Once depletion is achieved, gradually increasing amounts of the nutrient under study are added to the diet until the individual shows evidence of sufficiency or repletion.
inflammation of the skin. This term is often used to describe a skin rash.
any skin disease, especially one not characterized by inflammation.
the layers of skin below the epidermis that support the epidermis in both structure and function. Although the majority of cells in this layer are fibroblasts supported by a collagen network, blood vessels, immune cells, and adipose tissue are also found in the dermis.
dual-energy X-ray absorptiometry. A precise instrument that uses the energy from very small doses of X-rays to determine bone mineral density (BMD) and to diagnose and follow the treatment of osteoporosis.
Diabetes mellitus
a chronic metabolic disease, characterized by abnormally high blood glucose (sugar) levels, resulting from the inability of the body to produce or respond to insulin. Type 1 diabetes mellitus, formerly known as insulin-dependent or juvenile-onset diabetes, is usually the result of autoimmune destruction of the insulin secreting β-cells of the pancreas. The most common form of diabetes is type 2 diabetes mellitus, formerly known as noninsulin-dependent or adult onset diabetes, which develops when the tissues of the body become less sensitive to insulin secreted by the pancreas.
Diabetic ketoacidosis
a potentially life-threatening condition characterized by ketosis (elevated levels of ketone bodies in the blood) and acidosis (increased acidity of the blood). Ketoacidosis occurs when diabetes is not adequately controlled.
a medical procedure to filter waste products from the blood. Dialysis is needed to perform the work of the kidneys if they can no longer function effectively. Two types of dialysis are hemodialysis and peritoneal dialysis.
Diastolic blood pressure
the lowest arterial blood pressure during the heart beat cycle, and the second number in a blood pressure reading (e.g., 120/80).
changes in a cell resulting in its specialization for specific functions, such as those of a nerve cell. In general, differentiation of cells leads to a decrease in proliferation.
a passive process, in which particles in solution move from a region of higher concentration to one of lower concentration.
a complex of two molecules, usually proteinsHeterodimers are complexes of two different molecules, while homodimers are complexes of two of the same molecule.
an agent that increases the formation of urine by the kidneys, resulting in water loss from the individual using the diuretic. 
inflammation or infection of diverticula in the colon (see diverticulosis), characterized by abdominal pain, fever, and constipation. 
a condition characterized by the formation of small pouches (diverticula) in the colon. Although most people with diverticulosis experience no symptoms, about 15-20% may develop pain or inflammation, known as diverticulitis
deoxyribonucleic acid; a double-stranded nucleic acid composed of many nucleotides. The nucleotides in DNA are each composed of a nitrogen-containing base (adenine, guanine, cytosine, or thymine), a five-carbon sugar (deoxyribose), and a phosphate group. The sequence of bases in DNA encodes the genetic information required to synthesize proteins.
DNA adduct
the complex formed when a chemical forms a covalent bond with DNA.
Dominant trait
a trait that is expressed when only one copy of the gene responsible for the trait is present.
refers to a study in which neither the investigators administering the treatment nor the participants know which participants are receiving the experimental treatment and which are receiving the placebo.
dietary reference intake. Refers to a set of at least four nutrient-based reference values (RDA, AI, UL, EAR), each with a specific use in defining recommended dietary intake levels for individual nutrients in the US. The DRIs are determined by expert panels appointed by the Food and Nutrition Board of the Institute of Medicine.
daily value. Refers to the dietary reference values required as the basis for declaring nutrient content on all products regulated by the US Food and Drug Administration (FDA), including nutritional supplements. The DVs for vitamins and minerals reflect the most up-to-date Dietary Reference Intakes.
an imbalance of intestinal microbiota.
impaired control of voluntary movement. Dyskinesia is sometimes a side effect of long-term use of antipsychotic medications.
a disorder of lipoprotein metabolism.

Glossary: E

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estimated average requirement; a nutrient intake value that is estimated to meet the requirement of half of the healthy individuals in a particular life stage and gender group.
a diagnostic test that uses ultrasound to make images of the heart. It can be used to assess the health of the valves and chambers of the heart, as well as to measure cardiac output.
seizures in a woman caused by pregnancy-induced hypertension; a significant cause of maternal mortality.
Ecologic study
an epidemiological study that examines the relationships between exposures and disease rates in a series of populations (e.g., different countries). Ecologic studies often rely on published statistics, such as food disappearance data or disease-specific death rates.
swelling; accumulation of excessive fluid in subcutaneous tissues (beneath the skin).
a chemical messenger derived from a 20-carbon polyunsaturated fatty acid, such as arachidonic acid and eicosapentaenoic acid. Eicosanoids play critical roles in immune and inflammatory responses.
a flexible structural protein similar to collagen; elastin is found in the dermal layer of skin and other parts of the body.
Electrocardiogram (ECG)
a recording of the electrical activity of the heart, used to diagnose cardiac arrhythmias, myocardial ischemia and myocardial infarction.
Electroencephalogram (EEG)
a recording of the electrical activity of the brain, used to diagnose neurological conditions like seizure disorders (epilepsy).
ionized (dissociated into positive and negative ions) salts in the body fluids. Major electrolytes in the body include sodium, potassium, magnesium, calcium, chloride, bicarbonate, and phosphate.
a stable atomic particle with a negative charge.
Electron transport chain
a group of electron carriers in mitochondria that transport electrons to and from each other in a sequence, in order to generate ATP.
one of the 103 chemical substances that cannot be divided into simpler substances by chemical means. For example, hydrogen, magnesium, lead, and uranium are all chemical elements. Trace elements are chemical elements that are required in very small (trace) amounts in the diet to maintain health. For example, copper, selenium, and iodine are considered trace elements.
a chronic obstructive pulmonary (lung) disease, characterized by damage to the small air sacs (alveoli) and difficulty breathing. Damage to the alveoli decreases their elasticity and results in hyperinflation of the lungs, which impairs gas exchange. Smoking is the most common cause of emphysema.
the hard, white, outermost layer of a tooth.
either of two optical isomers that are mirror images of each other.
a disease of the brain that alters brain function.
Endocrine system
the glands and parts of glands that secrete hormones that integrate and control the body's metabolic activity. Endocrine glands include the pituitary, thyroid, parathyroids, adrenals, pancreas, ovaries, and testes.
A type of cellular uptake that involves invagination of the cell membrane at the site of ligand binding followed by internalization of the substance inside a membrane-bound vesicle.
arising from within the body. Endogenous synthesis refers to the synthesis of a compound by the body.
the inner lining of the uterus.
Endothelium-dependent vasodilation
arterial vasodilation resulting from the production of nitric oxide in the vascular endothelium.
toxins released by certain bacteria.
the addition of nutrients to replace losses that may occur in food processing.
a cell that lines the luminal (inner) surface of the intestine.
a biological catalyst; that is, a substance that increases the speed of a chemical reaction without being changed in the overall process. Enzymes are vitally important to the regulation of the chemistry of cells and organisms.
Epidemiological study
a study examining disease occurrence in a human population.
the outer layers of skin above the dermis. The epidermis consists of overlapping layers of keratinocytes in various stages of development, eventually forming the barrier that protects underlying cell layers from the environment.
a system of tubules emerging from the testes, which serves as a storage site for sperm during their maturation.
also known as seizure disorder. Individuals with epilepsy experience seizures, which are the result of uncontrolled electrical activity in the brain. A seizure may cause a physical convulsion, minor physical signs, thought disturbances, or a combination of symptoms.
layer of cells that lines a body cavity or covers an external surface of the body.
reddening of the skin; often used as an indice of inflammation caused by ultraviolet exposure.
red blood cell.
relating to erythrocytes.
the production of red blood cells.
a hormone produced by specialized cells in the kidneys that stimulates the bone marrow to increase the production of red blood cells. Recombinant erythropoietin is used to treat anemia in patients with end stage renal failure.
the portion of the gastrointestinal tract that connects the throat (pharynx) to the stomach.
the product of a reaction between a carboxylic acid and an alcohol that involves the elimination of water. For example a cholesterol ester is the product of a reaction between a fatty acid and cholesterol.
a hormone that binds to estrogen receptors in the nuclei of cells and promotes the transcription of estrogen-responsive genes. Endogenous estrogens are steroid hormones produced by body. Exogenous estrogens are synthetic or natural compounds that have estrogenic activity (i.e., bind the estrogen receptor and promote estrogen-responsive gene transcription).
the causes or origin of a disease.
normal blood glucose concentrations.
the toxicity that results from the continuous stimulation of nerve cells by neurotransmitters.
the elimination of wastes from blood or tissues.
Executive function
a set of mental processes that helps connect past experience with present action. Executive functions include planning, organizing, strategizing, remembering details, and managing time and space.
benign outgrowth of bone from the surface of an existing bone.
Extracellular fluid (ECF)
the volume of body fluid excluding that in cells. ECF includes the fluid in blood vessels (plasma) and fluid between cells (interstitial fluid).
Ex vivo
"outside a living organism."

Glossary: F

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Familial adenomatous polyposis
a hereditary syndrome characterized by the formation of many polyps in the colon and rectum, some of which may develop into colorectal cancer.
Fatty acid
an organic acid molecule consisting of a chain of carbon molecules and a carboxylic acid (-COOH) group. Fatty acids are found in fats, oils, and as components of a number of essential lipids, such as phospholipids and triglycerides. Fatty acids can be burned by the body for energy.
Femoral neck
a portion of the thighbone (femur). The femoral neck is found near the hip, at the base of the head of femur, which makes up the ball of the hip joint. Fractures of the femoral neck sometimes occur in individuals with osteoporosis.
Fetal macrosomia
a newborn of birth weight >4,000 grams (>8 pounds 13 ounces).
an anaerobic process that involves the breakdown of dietary components to yield energy.
a cell that secretes extracellular matrix proteins, such as collagen, which give skin its structure. These cells are mostly found in the dermis and connective tissue.
Fibrocystic breast changes (FCC)
a benign (noncancerous) condition of the breasts, characterized by lumpiness and discomfort in one or both breasts.
First-pass metabolism
a phenomenon of drug metabolism whereby the concentration of a drug is greatly reduced before it reaches the systemic circulation due to action from the gastrointestinal tract and liver.
Food frequency questionnaire
a method of dietary assessment in which study participants are given a validated list of food and beverages and asked to report the frequency and portion size consumed over a given period of time.
Forced expiratory volume (FEV1)
the volume of air that can be expelled during the first second of a forced expiration. FEV1 is used to assess pulmonary (lung) function.
the addition of nutrients to foods to prevent or correct a nutritional deficiency.
a break in a bone or cartilage, often but not always the result of trauma.
Free radical
a very reactive atom or molecule typically possessing a single unpaired electron.
describes a group of circulating proteins that have become irreversibly bound to glucose. Fructosamine assays provide information about blood glucose control two to three weeks prior to sample collection.
a very sweet six-carbon sugar abundant in plants. Fructose is increasingly common in sweeteners such as high-fructose corn syrup.

Glossary: G

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a small sac adjacent to the liver. The gallbladder stores bile, which is secreted by the liver, and releases it into the small intestine through the common bile duct.
crystals formed by the precipitation of cholesterol or bilirubin in the gallbladder. Gallstones may be asymptomatic (without symptoms) or they may result in inflammation and infection of the gallbladder.
pertaining to the stomach.
Gastric mucosa
a mucus membrane lining of the interior of the stomach that protects the underlying stomach tissue.
inflammation of the lining of the stomach.
Gastroesophageal reflux disease (GERD)
a condition in which stomach contents, including acid, back up (reflux) into the esophagus, causing inflammation and damage to the esophagus. GERD can lead to scarring of the esophagus and may increase the risk of cancer of the esophagus in some patients.
referring to or affecting the digestive tract, which includes the mouth, pharynx (throat), esophagus, stomach, and intestines.
a region of DNA that controls a specific hereditary characteristic, usually corresponding to a single protein.
Gene expression
the process by which the information coded in genes (DNA) is converted to proteins and other cellular structures. Expressed genes include those that are transcribed to mRNA and translated to protein, as well as those that are only transcribed to RNA (e.g., ribosomal and transfer RNAs).
all of the genetic information (encoded in DNA) possessed by an organism.
the genetic makeup of an individual cell or organism.
the period of time between fertilization and birth. In humans, normal gestation is about 40 weeks.
the soft tissue lining the mouth (i.e., gums).
inflammation of the gingiva.
Glomerulus (plural glomeruli)
a tuft of capillaries that makes up part of the filtering unit of the kidney (nephron).
the production of glucose from non-carbohydrate precursors, such as amino acids (the building blocks of proteins).
a six-carbon sugar which plays a major role in the generation of energy for living organisms.
Glucose tolerance
the ability of the body to maintain normal glucose levels when challenged with a carbohydrate load (see impaired glucose tolerance).
a glycoside that contains glucose as its carbohydrate (sugar) moiety.
an excitatory neurotransmitter. Under certain circumstances glutamate may become toxic to neurons. Glutamate excitotoxicity appears to play a role in nerve cell death in some neurodegenerative disorders.
a tripeptide consisting of glutamate, cysteine, and glycine. Glutathione is an endogenous, intracellular antioxidant and is also required for some phase II biotransformation reactions.
Glycated hemoglobin
glucose-bound hemoglobin. A test for glycated hemoglobin measures the percentage of hemoglobin that is glucose bound. Since glucose remains bound to hemoglobin for the life of a red blood cell (~120 days), glycated hemoglobin values reflect blood glucose control over the past four months.
Glycemic index (GI)
an index of the blood glucose-raising potential of the carbohydrate in different foods. The GI is calculated as the area under the blood glucose curve after a test food is eaten, divided by the corresponding area after a control food (glucose or white bread) is eaten. The value is multiplied by 100 to represent a percentage of the control food.
Glycemic load (GL)
an index that simultaneously describes the blood glucose-raising potential of the carbohydrate in a food and the quantity of carbohydrate in a food. The GL of a food is calculated by multiplying the GI by the amount of carbohydrate in grams provided by a food and dividing the total by 100.
a large polymer (repeating units) of glucose molecules, used to store energy in cells, especially muscle and liver cells.
the metabolic pathway in the cytosol that degrades glucose, producing energy in the form of ATP.
a compound containing a sugar molecule that can be cleaved by hydrolysis to a sugar and a nonsugar component (aglycone).
enlargement of the thyroid gland. Goiter is one of the earliest and most visible signs of iodine deficiency. The thyroid enlarges in response to persistent stimulation by TSH. In mild iodine deficiency, this adaptive response may be enough to provide the body with sufficient thyroid hormone. However, more severe cases of iodine deficiency result in hypothyroidism. Thyroid enlargement may also be caused by factors other than iodine deficiency, especially in iodine sufficient countries, such as the US.
a substance that induces goiter formation by interfering with thyroid hormone production or utilization.
a condition characterized by abnormally high blood levels of uric acid (urate). Urate crystals may form in joints, resulting in inflammation and pain. Urate crystals may also form in the kidney and urinary tract, resulting in kidney stones. The tendency to develop elevated blood uric acid levels and gout is often inherited.
Granular layer
the layer of the epidermis below the stratum corneum.
Gray matter
the darker-colored tissue in the central nervous system that contains mostly cell bodies and dendrites.
guanosine triphosphate. A high-energy molecule, required for a number of biochemical reactions, including nucleic acid and protein synthesis (formation).

Glossary: H

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a set of DNA variations (polymorphisms) at adjacent locations on a chromosome; these DNA variations are inherited together.
Hartnup disease
a genetic disorder resulting in defective absorption of the amino acid, tryptophan.
high-density lipoproteins. HDL transport cholesterol from the tissues to the liver where it can be eliminated in bile. HDL-cholesterol is considered "good cholesterol," because higher blood levels of HDL-cholesterol are associated with lower risk of cardiovascular disease.
the percentage of red blood cells in whole blood.
the branch of medicine that studies the nature, function, disorders, and diseases of the blood, spleen, and lymph glands.
compounds of iron complexed in a characteristic ring structure known as a porphyrin ring.
the process of removing blood from an artery, removing waste products from the blood through dialysis, and returning blood to the body through a vein. Hemodialysis is used to treat end-stage renal failure.
the oxygen-carrying pigment in red blood cells.
Hemoglobin A1c
the main fraction of glycated (glucose-bound) hemoglobin. Since glucose remains bound to hemoglobin for the life of a red blood cell (~120 days), hemoglobin A1C values reflect blood glucose control over the past four months.
rupture of red blood cells.
Hemolytic anemia
anemia resulting from hemolysis.
excessive or uncontrolled bleeding.
Hemorrhagic stroke
a stroke that occurs when a blood vessel ruptures and bleeds into the brain.
dilated or enlarged veins of the anus and lower rectum.
the arrest of bleeding.
relating to the liver.
Hepatic encephalopathy
a spectrum of neuropsychiatric signs or symptoms in individuals with acute or chronic liver disease.
literally, inflammation of the liver. Hepatitis caused by a virus is known as viral hepatitis. Other causes of hepatitis include toxic chemicals and alcohol abuse.
Hepatocellular carcinoma
the most common type of primary liver cancer.
a parenchymal cell of the liver.
an abnormally enlarged liver.
Hereditary hemochromatosis
a genetic disorder that results in iron overload despite normal dietary intake of iron.
Hereditary spherocytosis
a hereditary form of anemia characterized by abnormally shaped red blood cells which are spherical and abnormally fragile. The increased fragility of these red blood cells leads to hemolytic anemia (anemia caused by the rupture of red blood cells).
a dimer or complex of two different molecules, usually proteins.
variability in study design and outcomes; the quality of being diverse and not comparable.
possessing two different forms (alleles) of a specific gene.
the study of cells and tissues at the microscopic level.
protein that binds to DNA and packages it into compact structures to form nucleosomes.
human immunodeficiency virus; the virus that causes AIDS.
a state of balance.
a sulfur-containing amino acid, which is an intermediate in the metabolism of another sulfur-containing amino acid, methionine.  Elevated homocysteine levels in the blood have been associated with increased risk of cardiovascular disease.
a dimer or complex of two of the same molecule, usually a protein.
having the same appearance, structure, or evolutionary origin.
possessing two identical forms (alleles) of a specific gene.
a chemical released by a gland or a tissue, which affects or regulates the activity of specific cells or organs. Complex bodily functions, such as growth and sexual development, are regulated by hormones.
Hot flushes
sensations of heat in the skin, particularly the face, neck, and chest; also known as hot flashes. Hot flushes are most often related to declining estrogen levels during the perimenopause (period surrounding menopause).
Human papilloma virus (HPV)
a group of viruses that may cause papillomas (growths or warts) on the skin or other parts of the body, including the genitals and the larynx (voice box). Infection with particular strains of HPV is associated with increased risk of cervical cancer.
Huntington's disease
an inherited degenerative disorder of the brain. Its symptoms include movement disorders and impaired cognitive function. Symptoms of Huntington's disease, previously known as Huntington's chorea, typically develop in the fourth decade of life and progressively deteriorate over time.
cleavage of a chemical bond by the addition of water. In hydrolysis reactions, a large compound may be broken down into smaller compounds when a molecule of water is added.
a molecule that has a high affinity for water and will readily dissolve in water.
Hydrophobic (lipophilic)
a molecule that repels water and thus will not dissolve in water.
a calcium phosphate salt. Hydroxyapatite is the main mineral component of bone and teeth and is what gives them their rigidity.
a chemical reaction involving the addition of a hydroxyl (-OH) group to a compound.
an abnormally high blood glucose concentration; symptoms include increased thirst, increased urination, and general fatigue.
abnormally elevated blood levels of homocysteine; associated with increased risk of cardiovascular disease.
excessively high levels of plasma homocysteine.
irregular thickening of the stratum corneum due to increased number of corneocyte layers.
an abnormally high concentration of lipids in the blood.
refers to increased interactions between β-amyloid peptides and copper in Alzheimer's disease.
excessive growth of bone tissue.
excess secretion of parathyroid hormone by the parathyroid glands resulting in the disturbance of calcium metabolism. Symptoms may include increased blood levels of calcium (hypercalcemia), decreased blood levels of phosphorus, loss of calcium from bone, and kidney stone formation.
excessive cell growth.
high blood pressure. According to the 2017 Clinical Practice Guidelines, hypertension is defined as a systolic blood pressure of 130 mm Hg or higher or a diastolic blood pressure of 80 mm Hg or higher. 
an excess of thyroid hormone which may result from an overactive thyroid gland or nodule, or from taking too much thyroid hormone.
the enlargement of a tissue or organ due to an increase in the size of its cells.
an abnormally low blood glucose concentration. Symptoms may include nausea, sweating, weakness, faintness, confusion hallucinations, headache, loss of consciousness, convulsions, or coma.
a deficiency of parathyroid hormone, which may be characterized by low blood calcium levels (hypocalcemia).
an area at the base of the brain that regulates bodily functions, such as body temperature, hunger, and thirst.
an educated guess or proposition that is advanced as a basis for further investigation. A hypothesis must be subjected to an experimental test to determine its validity.
a deficiency of thyroid hormone that is normally made by the thyroid gland, located in the front of the neck.

Glossary: I

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of unknown cause. 
a surgically created connection between the ileum (part of the small intestine) and an opening in the abdominal wall (stoma) that allows for the evacuation of feces when a portion of the bowel has been removed.
the third and final section of the small intestine.
Impaired glucose tolerance
a metabolic state between normal glucose regulation and overt diabetes. Impaired glucose tolerance is defined medically as a plasma glucose concentration between 140 and 199 mg/dL (7.8-11.0 mmol) two hours after the ingestion of 75 g of glucose during an oral glucose tolerance test.
inability to control the evacuation of urine or feces.
initiation of or increase in the expression of a gene in response to a physical or chemical stimulus (inducer).
a response to injury or infection, characterized by redness, heat, swelling, and pain. Physiologically, the inflammatory response involves a complex series of events, leading to the migration of white blood cells to the inflamed area.
Inflammatory bowel disease
a group of autoimmune diseases that affect the small and large intestines.
not dissolvable. With respect to bioavailability, certain substances form insoluble complexes that cannot be dissolved in digestive secretions, and therefore cannot be absorbed by the digestive tract.
a peptide hormone secreted by the β-cells of the pancreas required for normal glucose metabolism.
Insulin resistance
diminished responsiveness to insulin.
Insulin sensitivity
the ability of tissues to respond to insulin.
Intermittent claudication
a condition characterized by leg pain or weakness on walking that diminishes or resolves with rest. It is usually associated with peripheral arterial disease.
International normalized ratio (INR)
the preferred method for reporting prothrombin time, a measure of coagulation status that may be used to evaluate the therapeutic efficacy of anticoagulants, such as warfarin. The INR is a method for standardizing prothrombin time results so as to minimize variability between laboratories.
Intervention trial
an experimental study (usually a clinical trial) used to test the effect of a treatment or intervention on a health- or disease-related outcome.
Intestinal microbiota
the collection of microbial species that live specifically in the lower gastrointestinal tract (colon).
Intracellular fluid (ICF)
the volume of fluid inside cells.
Intraperitoneal (ip) injection
injection into the peritoneum.
within a vein.
Inverse association
a relationship between two variables in which they move in opposite directions.
In vitro
literally "in glass," referring to a test or research done in the test tube, outside a living organism.
In vivo
"inside a living organism." An in vivo assay evaluates a biological process occurring inside the body.
an atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons.
Ion channel
a protein embedded in a cell membrane that serves as a crossing point for the regulated transfer of an ion or a group of ions across the membrane.
a state of insufficient blood flow to a tissue.
Ischemic stroke
a stroke resulting from insufficient blood flow to an area of the brain, which may occur when a blood vessel supplying the brain becomes obstructed by a clot.
having the same caloric density.
one of two or more compounds that has the same number and kind of atoms but differs in the way the atoms are arranged.
a different form of the same chemical element. Isotopes have the same number of protons but different numbers of neutrons.

Glossary: J, K

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a yellowish staining of the skin and whites of the eyes due to increased bilirubin (a bile pigment) levels in the blood. Jaundice can be an indicator of red blood cells rupturing (hemolysis), or disease of the liver or gallbladder.
the process of cell differentiation of a keratinocyte through the different layers of the epidermis. At the end of keratinization, the cell is wider and flatter and attached to its neighboring cells by a variety of protein and lipid attachments.
primary cell type of the epidermis; these cells produce the structural protein keratin, which comprise the epidermal barrier.
Ketone bodies
any of three acidic chemicals (acetate, acetoacetate, and β-hydroxybutyrate). Ketone bodies may accumulate in the blood (ketosis) when the body has inadequate glucose to use for energy and must increase the use of fat for fuel. Ketone bodies are acidic, and very high levels in the blood are toxic and may result in ketoacidosis.
Kidney stones
solid masses resulting from the crystallization of minerals and other compounds found in urine. Common types of kidney stones include those composed of calcium oxalate, calcium phosphate and urate. Kidney stones may form in the kidneys, ureters, or urinary bladder.

Glossary: L

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Langerhan cell
an antigen-presenting cell involved in epidermal immunity.
spasm that causes closure of the larynx, interfering with breathing.
the area of the throat (pharynx) that contains the vocal cords.
low-density lipoprotein. LDLs transport cholesterol from the liver to the tissues of the body. Elevated serum LDL-cholesterol is associated with increased cardiovascular disease risk.
Left ventricular hypertrophy (LVH)
abnormal thickening of the wall of the left ventricle (lower chamber) of the heart muscle. The ventricles have muscular walls in order to pump blood from the heart through the arteries, but LVH occurs when the ventricle must pump against abnormally high volume or pressure loads. LVH may accompany congestive heart failure (CHF).
members of the large family of plants known as leguminosae. In this context the term refers to the fruit or seeds of leguminous plants (e.g., peas and beans) that are used for food.
the transparent structure inside the eye that focuses light rays onto the retina (the nerve cells at the back of the eye).
hormone secreted by adipose tissue that helps to regulate of food intake, body weight, and energy homeostasis.
Leptin resistance
resistance to the action of leptin.
an acute or chronic form of cancer that involves the blood-forming organs. Leukemia is characterized by an abnormal increase in the number of white blood cells in the tissues of the body, with or without a corresponding increase of those in the circulating blood, and is classified according to the type of white blood cell most prominently involved.
white blood cell. Leukocytes are part of the immune system. Monocytes, lymphocytes, neutrophils, basophils, and eosinophils are different types of leukocytes.
cell-signaling molecule involved in inflammation. Lipoxygenases catalyze the formation of leukotrienes from eicosanoids, such as arachidonic acid and eicosapentaenoic acid (EPA).
a substance that binds to another molecule, forming a complex.
Lipid peroxidation
the process by which lipids are oxidatively modified; so named because lipid hydroperoxides are formed in the process.
a chemical term for fat. Lipids found in the human body include fatty acids, phospholipids, and triglycerides.
the production of fatty acids.
Lipoic acid
a cofactor, essential for the oxidation of α-keto acids, such as pyruvate, in metabolism.
the breakdown of lipids by hydrolysis.
Lipoprotein(a) [Lp(a)]
a lipoprotein particle in which the protein (apolipoprotein B-100) is chemically linked to another protein apolipoprotein(a). Increased blood levels of Lp(a) are associated with an increased risk of cardiovascular disease.
particle composed of lipids and protein that allows for the transport of lipids through the bloodstream. A lipoprotein particle is composed of an outer layer of phospholipids, which renders it soluble in water, and a hydrophobic core that contains triglycerides and cholesterol esters. Different types of lipoproteins are distinguished by their surface proteins (apoproteins), their size, and the types and amounts of lipids they contain.
Lumbar spine
the portion of the spine between the chest (thorax) and the pelvis. It is commonly referred to as the small of the back.
the channel within a tube such as a blood vessel or the intestine.
see systemic lupus erythematosus (SLE).
leukocyte (white blood cells) that plays important roles in the immune system. T lymphocytes (T cells) differentiate into cells that can kill infected cells or activate other cells in the immune system. B lymphocytes (B cells) differentiate into cells that produce antibodies.
a cellular organelle containing hydrolytic enzymes specialized for breaking down cellular debris. Lysosomal enzymes are separated from the rest of the cell by a lysosomal membrane and function optimally at an acidic pH.

Glossary: M

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Macrocytic anemia
low red blood cell count, characterized by the presence in the blood of larger than normal red blood cells.
nutrients required in relatively large amounts; macronutrients include carbohydrates, proteins, and lipids.
white blood cell that engulfs and degrades pathogens (bacteria) and cellular debris. Macrophages are activated or transformed monocytes.
a small area of the retina where vision is the sharpest. The macula is located in the center of the retina and provides central vision.
Magnetic Resonance Imaging (MRI)
a special imaging technique that uses a powerful magnet and a computer to provide clear images of soft tissues. Tissues that are well-visualized using MRI include the brain and spinal cord, abdomen, and joints.
Malabsorption syndrome
a disease or condition that results in poor absorption of nutrients from food.
an infectious disease caused by parasitic microorganisms called plasmodia. Malaria can be spread among humans through the sting of certain types of mosquitos (Anopheles) or by a contaminated needle or transfusion. Malaria is a major health problem in the tropics and subtropics, affecting over 200 million people worldwide.
Matrix metalloproteinase (MMP)
a proteolytic enzyme that degrades extracellular matrix proteins, such as collagen and elastin.
M cells
membranous or microfold cells; specialized cells in the intestinal epithelium that internalize pathogenic microorganisms to the gut-associated lymphoid tissue.
Measurement error
the difference between a measured value and its true value.
Megaloblastic anemia
low red blood cell count, characterized by the presence in the blood of large, immature, nucleated cells (megaloblasts) that are forerunners of red blood cells. Red blood cells, when mature, have no nucleus.
a dark brown pigment found in the skin.
a pigment-containing cell of the epidermis. The pigment, melanin, absorbs ultraviolet light and protects the skin from damage. Unlike keratinocytes, melanocytes are not shed over time.
Membrane potential
the electrical potential difference across a membrane. The membrane potential is a result of the concentration differences between potassium and sodium across cell membranes, which are maintained by ion pumps. A large proportion of the body's resting energy expenditure is devoted to maintaining the membrane potential, which is critical for nerve impulse transmission, muscle contraction, heart function, and the transport of nutrients and metabolites in and out of cells.
the first occurrence of menstruation.
Mendelian randomization study
genetic study conducted to assess whether genetic determinants of a risk factor are related to clinical outcomes.
the permanent cessation of menstruation.
the cyclic loss of blood by a woman from her uterus (womb) when she is not pregnant. Menstruation generally occurs every four weeks after a woman has reached sexual maturity and prior to menopause.
a statistical technique used to combine the results from different studies to obtain a quantitative estimate of the overall effect of a particular intervention or exposure on a defined outcome.
Metabolic syndrome
a combination of medical conditions that places one at risk for cardiovascular disease and type 2 diabetes. (Metabolic syndrome is also called metabolic syndrome X, syndrome X, and insulin resistance syndrome.) Diagnostic criteria include the presence of three or more of the following conditions:
  • Abdominal obesity (waist circumference: ≥40 inches [102 cm] for men, ≥35 inches [88 cm] for women)
  • Elevated triglycerides (≥150 mg/dL or on drug treatment for elevated triglycerides)
  • High blood pressure (≥130 mm Hg for systolic blood pressure and/or ≥85 mm Hg for diastolic blood pressure, or taking anti-hypertensive drugs)
  • Glucose intolerance/insulin resistance (fasting blood glucose ≥100 mg/dL, or on drug treatment for elevated glucose)
  • Decreased HDL cholesterol (<40 mg/dL for men and <50 mg/dL for women, or on drug treatment for low HDL cholesterol)
the sum of the processes (reactions) by which a substance is assimilated and incorporated into the body or detoxified and excreted from the body.
a compound derived from the metabolism of another compound is said to be a metabolite of that compound.
to spread from one part of the body to another. Cancer is said to metastasize when it spreads from the primary site of origin to a distant anatomical site.
a sulfur containing amino acid, required for protein synthesis and other vital metabolic processes. It can be obtained through the diet in protein or synthesized from homocysteine.
a biochemical reaction resulting in the addition of a methyl group (-CH3) to another molecule.
an aggregate or cluster of amphipathic molecules in water. Amphipathic molecules have a polar or hydrophilic end and a nonpolar or hydrophobic end. In micelles, amphipathic molecules orient with their hydrophobic ends in the interior and their hydrophilic ends on the exterior surface, exposed to water.
a nutrient required by the body in small amounts, such as a vitamin or a mineral.
small non-coding RNA involved in the regulation of gene expression.
underdevelopment of the external ear.
Migraine headache
a type of headache thought to be related to abnormal sensitivity of blood vessels (arteries) in the brain to various triggers resulting in rapid changes in the artery size due to spasm (constriction). Other arteries in the brain and scalp then open (dilate), and throbbing pain is perceived in the head. The tendency toward migraine appears to involve serotonin, a neurotransmitter that can trigger the release of vasoactive substances in the blood vessels.
nutritionally significant element. Elements are composed of only one kind of atom. Minerals are inorganic, i.e., they do not contain carbon as do vitamins and other organic compounds.
Minimal Erythemal Dose (MED)
the lowest dose of ultraviolet radiation (UVR) that will produce a detectable erythema 24 hours after UVR exposure.
energy-producing structures within cells. Mitochondria possess two sets of membranes: a smooth continuous outer membrane and an inner membrane arranged in folds. Among other critical functions, mitochondria convert nutrients into energy via the electron transport chain.
the process of cell division.
mm Hg
millimeters of mercury. The unit of measure for blood pressure.
a portion of something, such as a functional group of a molecule.
the fundamental unit for measuring chemical compounds (abbreviated mol). One mole equals the molecular weight of a compound in grams. The number of molecules in a mole is equal to 6.02 x 1023 (Avogadro's number).
Molecular chaperone
a class of proteins that facilitates in the folding and assembly of other proteins.
white blood cell that is the precursor to a macrophage.
a molecule that can be chemically bound as a unit of a polymer.
the use of a single medication to treat a condition.
Monounsaturated fatty acid
a fatty acid with only one double bond between carbon atoms.
short for messenger ribonucleic acid (RNA). These molecules are the ‘message’ that encodes the proteins produced in cells. Increases or decreases in mRNA levels will alter protein production in cells.
a glycoprotein that lubricates and protects body surfaces.
relating to the mucous membranes of the skin.
refers to diseases or conditions that are the result of interactions between multiple genetic and environmental factors.
Multiple sclerosis (MS)
an autoimmune disorder in which the myelin sheaths of nerves in the brain and spinal cord are damaged, resulting in progressive neurological symptoms.
an agent that can induce mutation.
a change in a gene; in other words, a change in the sequence of base-pairs in the DNA that makes up a gene. Mutations in a gene may or may not result in an altered gene product.
the fatty substance that covers myelinated nerves. Myelin is a layered tissue surrounding the axons or nerve fibers. This sheath acts as a conduit in an electrical system, allowing rapid and efficient transmission of nerve impulses.
the formation of the myelin sheath around a nerve fiber.
derived from bone marrow.
Myocardial infarction (MI)
death (necrosis) of heart muscle tissue due to an interruption in its blood supply. Commonly known as a heart attack, an MI usually results from the obstruction of a coronary artery by a clot in people who have coronary atherosclerosis.
Myocardial stunning
a temporary dysfunction of the cardiac myocardium (contractile abormality) following ischemia and reperfusion.
an inflammation of the heart muscle.
muscle cell.
a heme-containing pigment in muscle cells that binds and stores oxygen.
any disease of muscle.

Glossary: N

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Natural killer (NK) cells
cytotoxic lymphocytes important for the innate immune response that kills pathogens. NK cells also have important roles in killing cancer cells.
unprogrammed cell death, in which cells break open and release their contents, promoting inflammation. Necrotic cell death may be the result of injury, infection, or infarction.
a term referring to a rapid and abnormal growth of tissue. Neoplasms can be benign or malignant.
kidney damage or disease.
Nerve impulse
the electrochemical signal transmitted in the cell membrane of a neuron or muscle cell. Also called action potential.
Nested case-control study
a case-control study within a cohort study; cases of a disease that occur in a defined cohort are identified, and a specified number of matched controls is then selected from the larger cohort for comparison.
Neural Tube Defect (NTD)
a birth defect caused by abnormal development of the neural tube, the structure which gives rise to the central nervous system. Neural tube defects include anencephaly and spina bifida.
Neurodegenerative disease
disease resulting from the degeneration or deterioration of nerve cells (neurons). Alzheimer's disease and Parkinson’s disease are neurodegenerative diseases.
the formation and development of nerves, nerve tissue, or the nervous system.
or neurological; involving nerves or the nervous system (brain, spinal cord, and all sensory and motor nerves).
cell of the nervous system that conducts nerve impulses. Also called nerve cell.
nerve damage or disease.
toxic or damaging to nervous tissue (brain and peripheral nerves). 
a chemical that is released from a nerve cell and results in the transmission of an impulse to another nerve cell or organ (e.g., a muscle). Acetylcholine, dopamine, norepinephrine, and serotonin are neurotransmitters.
an abnormally low number of neutrophils.
white blood cell that internalizes and destroys pathogens, such as bacteria. Neutrophils are also called polymorphonuclear leukocytes because they are white blood cells with multi-lobed nuclei.
US National Institutes of Health. Administered under the US Department of Health and Human Services (HHS), the NIH are more than 20 separate institutes and centers devoted to medical research.
Nitric oxide
a gaseous signaling molecule synthesized from the amino acid arginine by enzymes called nitric oxide synthases. In the vascular endothelium, nitric oxide promotes arterial vasodilation.
having normal blood pressure, i.e., a systolic blood pressure <120 mm Hg and a diastolic blood pressure <80 mm Hg.
Nucleic acid
DNA (deoxyribonucleic acid) and RNA (ribonucleic acid); long polymer of nucleotides.
repeating unit of chromatin that consists of DNA that is coiled around histones.
a compound composed of a nitrogen-containing base (adenine, guanine, cytosine, uracil, or thymine) linked to either ribose or deoxyribose.
subunit of nucleic acids. Nucleotides are composed of a nitrogen-containing base (adenine, guanine, cytosine, uracil, or thymine), a five-carbon sugar (ribose or deoxyribose), and one or more phosphate groups.
a membrane-bound cellular organelle, which contains DNA organized into chromosomes.

Glossary: O

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a condition of increased body fat; defined as a body mass index (BMI) ≥30 for adults.
Observational study
a study in which no experimental intervention or treatment is applied. Participants are simply observed over time.
relating to the eye.
Odds ratio (OR)
a measure of association comparing the odds of an outcome in the exposed group to the odds of an outcome in the non-exposed (control) group. The OR is an approximation of the relative risk.
Omega-3 index
the amount of eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) in red blood cell membranes expressed as the percent of total red blood cell membrane fatty acids.
the field of medicine dealing with cancer and tumors.
One-carbon unit
a biochemical term for functional groups containing only one carbon in addition to other atoms. One-carbon units transferred by folate coenzymes include methyl (-CH3), methylene (-CH2-), formyl (-CH=O), formimino (-CH=NH), and methenyl (-CH=).  Many biosynthetic reactions involve the addition of a one-carbon unit to a precursor molecule.
Open-label trial
a clinical trial in which the investigators and participants are aware of the treatment (i.e., it is not double-blind).
Optimum health
in addition to freedom from disease, the ability of an individual to function physically and mentally at his or her best.
Oral (po) administration
administration of a substance by mouth.
a specialized component of a cell, such as the mitochondrian or lysosome, so named because they are analogous to organs.
refers to carbon-containing compounds, generally synthesized by living organisms.
a term used to describe the mouth and throat.
a degenerative joint condition that is characterized by the breakdown of articular cartilage (cartilage within the joint).
bone cell that is responsible for the formation of new bone mineral in the bone remodeling process.
bone cell that is responsible for the breakdown or resorption of bone in the bone remodeling process.
a type of bone cell formed from an osteoblast once it becomes embedded deep within the organic matrix.
a disease of adults that is characterized by softening of the bones due to loss of bone mineral. Osteomalacia is characteristic of vitamin D deficiency in adults, while children with vitamin D deficiency suffer from rickets.
death of bone tissue.
a condition of low bone mass clinically defined as having a T-score one to 2.5 standard deviations (SD) below that of the average young adult (30 years of age) female.
a condition of increased bone fragility and susceptibility to bone fracture due to a loss of bone mineral density (BMD)
a form of malnutrition where nutrients are supplied in excess of the body’s needs.
reactive oxygen species.
a chemical reaction that removes electrons from an atom or molecule.
Oxidative damage
damage to cells caused by reactive oxygen species.
Oxidative stress
a condition, in which the effects of pro-oxidants (e.g., free radicals, reactive oxygen and reactive nitrogen species) exceed the ability of antioxidant systems to neutralize them.

Glossary: P,Q

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a small organ located behind the stomach and connected to the duodenum (part of the small intestine). The pancreas synthesizes enzymes that help digest food in the small intestine and hormones, including insulin, that regulate blood glucose levels.
Papillary dermis
the uppermost layer of the dermis.
Parathyroid glands
glands located behind the thyroid gland in the neck. The parathyroid glands secrete a hormone called parathyroid thormone (PTH) that is critical to calcium and phosphorus metabolism
Parenteral nutrition
intravenous administration of nutrition.
Parkinson's disease
a disease of the nervous system caused by degeneration of a part of the brain called the basal ganglia, as well as by low production of the neurotransmitter dopamine. Symptoms include muscle rigidity, tremors, and slow voluntary movement.
the state of being open or unobstructed.
disease-causing agents, such as viruses or bacteria.
the biological mechanisms underlying the development of a disease.
the branch of medicine that studies the causes and effects of disease.
Peptic ulcer disease
a disease characterized by ulcers or breakdown of the inner lining of the stomach or duodenum. Common risk factors for peptic ulcer disease include the use of nonsteroidal anti-inflammatory drugs (NSAIDs) and infection with Helicobacter pylori.
a chain of amino acids. A protein is made up of one or more peptides.
Peptide hormone
a hormone that is a protein, as opposed to a steroid hormone, which is made from cholesterol. Insulin is an example of a peptide hormone.
through the skin.
Percutaneous transluminal coronary angioplasty (PTCA)
a nonsurgical technique, in which a balloon catheter is inserted into a peripheral artery and passed into an occluded coronary artery, where the balloon is inflated to dilate the artery.
around the time of menopause; often refers to the transitional period before menopause.
the period of time just before and after birth (varyingly defined as the time period starting between 20 to 28 weeks’ gestation and ending one to four weeks after birth).
the tissues and gingiva surrounding the teeth.
Peripheral arterial disease
atherosclerosis of the arteries of the extremities.
Peripheral neuropathy
a disease or degenerative state affecting the nerves of the extremities (arms and legs). Symptoms may include numbness, pain, and muscle weakness.
Peripheral vascular disease
atherosclerosis of the vessels of the extremities, which may result in insufficient blood flow or pain in the affected limb, particularly during exercise.
Peritoneal dialysis
a procedure in which a special dialysis solution is introduced through a tube in the peritoneum. The dialysis solution pulls wastes and extra fluid from the body when the dialysis solution is drained through the same tube. The most common form is called continuous ambulatory peritoneal dialysis and can be performed at home without a machine.
a membrane that lines the walls of the abdominal cavity.
Pernicious anemia
the end stage of an autoimmune inflammation of the stomach, resulting in destruction of stomach cells by one's own antibodies.  Progressive destruction of the cells that line the stomach cause decreased secretion of acid and enzymes required to release food bound vitamin B12.  Antibodies to intrinsic factor (IF) bind to IF preventing formation of the IF-B12 complex, further inhibiting vitamin B12 absorption.
PET scan
positron emission tomography scan. A diagnostic imaging technique that uses a sophisticated camera and computer to produce images of how a person's body is functioning. A PET scan shows the difference between healthy and abnormally functioning tissues.
a measure of acidity or alkalinity.
a specialized cell, such as a macrophage, that engulfs and digests invading microorganisms through the process of phagocytosis.
process by which phagocytes engulf and digest invading microorganisms and foreign particles.
an intracellular vesicle containing the foreign material engulfed by the phagocyte.
the study of the absorption, distribution, metabolism, and elimination of drugs and other compounds.
Pharmacological dose
the dose or intake level of a nutrient many times the level associated with the prevention of deficiency or the maintenance of health. A pharmacologic dose is generally associated with the treatment of a disease state and considered to be a dose at least 10 times greater than that needed to prevent deficiency.
Phase I clinical trial
a clinical trial in a small group of people aimed at determining bioavailability, optimal dose, safety, and early evidence of the efficacy of a new therapy.
Phase II clinical trial
a clinical trial designed to investigate the effectiveness of a new therapy in larger numbers of people and to further evaluate short-term side effects and safety of the new therapy.
Phase III clinical trial
once a drug or treatment has been shown to be efficacious and safe in phase I and II clinical trials, a large, phase III clinical trial must be conducted before the drug or treatment receives formal FDA approval.
Phenolic compounds
a class of chemical compounds consisting of a hydroxyl functional group (-OH) attached to an aromatic hydrocarbon group. An aromatic hydrocarbon has a ring structure like that of benzene. Polyphenolic compounds contain more than one phenolic group.
Phenylketonuria (PKU)
an inherited disorder resulting in the inability to process the amino acid, phenylananine. If not treated, the disorder may result in mental retardation. Treatment is a diet low in phenylalanine. Newborns are screened for PKU, in order to determine the need for treatment before brain damage occurs.
the removal of blood from a vein. Phlebotomy may be used to obtain blood for diagnostic tests or to treat certain conditions, for example, iron overload in hemochromatosis.
lipid in which phosphoric acid, as well as fatty acids, are attached to a glycerol backbone. Phospholipids are important structural components of cell membranes.
the creation of a phosphate derivative of an organic molecule. This is usually achieved by transferring a phosphate group (-PO4) from ATP to another molecule.
skin damage induced by ultraviolet (UV) light that is absorbed in an uncontrolled manner by molecules in the body. Depending on the dose, UV light can cause cell death and an inflammatory response.
Physiologic dose
the dose or intake level of a nutrient associated with the prevention of deficiency or the maintenance of health.  A physiologic dose of a nutrient is not generally greater than that which could be achieved through a conscientious diet, as opposed to the use of supplements.
biologically active, non-nutrient compound synthesized by plants.
a plant-derived compound with estrogenic activity.
a compound that gives a plant or animal cell color by the selective absorption of different wavelengths of light.
Pilosebaceous unit
hair follicles in the skin that are associated with a sebaceous gland.
Pilot study
a preliminary study conducted on a small scale in order to prepare for a larger study.
Pituitary gland
a small oval gland located at the base of the brain that secretes hormones regulating growth and metabolism. The pituitary gland is divided into two separate glands, the anterior and posterior pituitary glands, which each secrete different hormones.
an inert treatment that is given to a control group while the experimental group is given the active treatment. Placebo-controlled studies are conducted to make sure that the results are due to the experimental treatment, rather than another factor associated with participating in the study.
the organ that connects the fetus to the pregnant woman's uterus, allowing for the exchange of oxygen, carbon dioxide, nutrients, and waste between woman and fetus.
Placental abruption
premature separation of the placenta from the wall of the uterus. Abruption is a potentially serious problem both for the woman and fetus.
whole blood without blood cells; that is, red blood cells and white blood cells have been removed. Plasma is separated from blood cells using a centrifuge. Unlike serum, plasma retains clotting factors because it is obtained from blood that is not allowed to clot.
irregularly shaped cell fragments that assist in blood clotting.
a disease of the lungs characterized by inflammation and accumulation of fluid in the lungs. Pneumonia may be caused by infectious agents (e.g., viruses or bacteria) or by inhalation of certain irritants.
a large molecule formed by combining many similar smaller molecules (monomers) in a regular pattern.
a nucleotide difference (variant) in the DNA sequence of a gene. Most polymorphisms are harmless and are part of normal human genetic variation, but some polymorphisms affect the function of the gene product (protein).
a benign (non-cancerous) mass of tissue that forms on the inside of a hollow organ, such as the colon.
Polyphenolic compound
a phenolic compound that contains more than one phenolic group.
Polyunsaturated fatty acid
a fatty acid with more than one double bond between carbons.
after eating or after a meal.
a non-digestible, fermentabl fiber that influences the composition of the intestinal microbiota.
a molecule which is an ingredient, reactant, or intermediate in a synthetic pathway for a particular product.
a condition characterized by a sharp rise in blood pressure during the third trimester of pregnancy. High blood pressure may be accompanied by edema (swelling) and proteinuria (protein in the urine). In some cases, untreated preeclampsia can progress to eclampsia, a life-threatening situation for the woman and child.
the proportion of a population with a specific disease or condition at a given point in time.
live cultures of microorganisms that, when administered in sufficient amounts, benefits the overall health of the host.
a carcinogen precursor that must be modified or metabolized to become an active carcinogen.
a precursor to a drug, i.e., an inactive compound that can be metabolized in the body to produc an active drug.
predicted outcome based on the course of a disease.
the reproduction or multiplication of cells.
DNA sequence to which RNA polymerase binds to initiate transcription.
an atom or molecule that promotes oxidation of another atom or molecule by accepting electrons. Examples of pro-oxidants include free radicals, reactive oxygen species (ROS), and reactive nitrogen species (RNS).
prevention, often refers to a treatment used to prevent a disease. 
Prospective cohort study
an observational study in which a group of people—known as a cohort—are interviewed or tested for risk factors (e.g., nutrient intake), and then followed up at subsequent times to determine their status with respect to a disease or health outcome.
cell-signaling molecule that is involved in inflammation. Cyclooxygenases catalyze the formation of prostaglandins from eicosanoids, such as arachidonic acid and eicosapentaenoic acid (EPA).
a gland in men, located at the base of the bladder and surrounds the urethra. The prostate produces fluid that forms part of semen. If the prostate becomes enlarged it may exert pressure on the urethra and cause urinary symptoms. Prostate cancer is one of the most common types of cancer in men.
Prostate-specific antigen (PSA)
a compound normally secreted by the prostate that can be measured in the blood. If prostate cancer is developing, the prostate secretes larger amounts of PSA. Blood tests for PSA are used to screen for prostate cancer and to follow up on prostate cancer treatment.
a complex organic molecule composed of amino acids in a specific order. The order is determined by the sequence of nucleic acids in a gene coding for the protein. Proteins are required for the structure, function, and regulation of the body's cells, tissues, and organs, and each protein has unique functions.
a large compound comprised of protein and polysaccharide units known as glycosaminoglycans (GAGs). GAGs are polymers of sugars and amino sugars, such as glucosamine or galactosamine. Proteoglycans are integral components of structural tissues like bone and cartilage.
the breakdown of proteins by protease enzymes.
an elementary particle identical to the nucleus of a hydrogen atom, which along with neutrons, is a constituent of all other atomic nuclei. A proton carries a positive charge equal and opposite to that of an electron.
a chronic skin condition often resulting in a red, scaly rash located over the surfaces of the elbows, knees, scalp, and around or in the ears, navel, genitals, or buttocks. Approximately 10-15% of patients with psoriasis develop joint inflammation (psoriatic arthritis). Psoriasis is thought to be an autoimmune condition.
Pyruvate kinase deficiency
a hereditary deficiency of the enzyme pyruvate kinase. Pyruvate kinase deficiency results in hemolytic anemia.
one-fourth of a sample or population.
one-fifth of a sample or population.

Glossary: R

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Racemic mixture
a mixture of equal amounts of isomers that are mirror images of each other (enantiomers).
Radiation therapy
the local use of radiation to destroy cancer cells or stop them from dividing and growing.
Randomized controlled trial (RCT)
a clinical trial with at least one active treatment group and a control (placebo) group. In RCTs, participants are chosen for the experimental and control groups at random and are not told whether they are receiving the active or placebo treatment until the end of the study. This type of study design can provide evidence of causality.
Randomized design
an experiment in which participants are chosen for the experimental and control groups at random, in order to reduce bias caused by self-selection into experimental and control groups. This type of study design can provide evidence of causality.
recommended dietary allowance. Established by the Food and Nutrition Board of the US Institute of Medicine, the RDA is the average daily dietary intake level of a nutrient sufficient to meet the requirements of nearly all healthy individuals in a specific life stage and gender group.
Reactive nitrogen species (RNS)
highly reactive chemicals, containing nitrogen, that react easily with other molecules, resulting in potentially damaging modifications.
Reactive oxygen species (ROS)
highly reactive chemicals, containing oxygen, that react easily with other molecules, resulting in potentially damaging modifications.
Recall bias
a type of measurement error caused by inaccuracies in the recollection of study participants regarding past behaviors and experiences.
a specialized molecule inside or on the surface of a cell that binds a specific chemical (ligand). Ligand binding usually results in a change in activity within the cell.
Recessive trait
a trait that is expressed only when two copies of the gene responsible for the trait are present.
the last portion of the large intestine, connecting the sigmoid colon (above) to the anus (below). The rectum stores stool until it is evacuated from the body.
Redox reaction
another term for an oxidation-reduction reaction. A redox reaction is any reaction in which electrons are removed from one molecule or atom and transferred to another molecule or atom. In such a reaction one substance is oxidized (loses electrons) while the other is reduced (gains electrons).
Reducing equivalent
an amount of a reducing compound that donates the equivalent of one mole of electrons or hydrogen ions in a redox reaction.
a chemical reaction in which a molecule or atom gains electrons.
a rapid process of cell growth by which the epidermis repairs itself after a wounding event. The goal of reepithelialization is to re-establish a functional barrier that protects underlying cells from environmental exposures.
Relative Risk (RR)
the probability of a negative outcome in the exposed group divided by the probability of the negative outcome in the non-exposed (control) group.
refers to the kidneys.
in nutrition, having fulfilled nutrient requirements.
Residual confounding
results when investigators fail to completely control for confounders by adjustment in statistical analyses.
a single unit within a polymer, such as an amino acid within a protein.
the process of breaking down or assimilating something. With respect to bone, resorption refers to the breakdown of bone by osteoclasts, resulting in the release of calcium and phosphate (bone mineral) into the blood.
Response element
a sequence of nucleotides in a gene that can be bound by a protein. Proteins that bind to response elements in genes are sometimes called transcription factors or binding proteins. Binding of a transcription factor to a response element regulates the production of specific proteins by inhibiting or enhancing the transcription of genes that encode those proteins.
with respect to the coronary arteries, restenosis refers to the reocclusion of a coronary artery after it has been dilated using coronary angioplasty.
the nerve layer that lines the back of the eye. In the retina, images created by light are converted to nerve impulses, which are transmitted to the brain via the optic nerve.
Retrospective study
an epidemiological study that looks back in time. A retrospective study begins after the exposure and the disease have occurred. Most case-control studies are retrospective.
Reverse causation
a concept that refers to the counterintuitive direction in a cause-and-effect association, when it is the effect that influences the cause; E.g., if low vitamin D status is common in people affected by multiple sclerosis (MS), it might be because those with MS spend less time outdoors and therefore synthesize less vitamin D in their skin (reverse causation), rather than because poor vitamin D status increases the risk of MS.
Rheumatoid arthritis
a chronic autoimmune disease characterized by inflammation of the synovial lining of the joints. Rheumatoid arthritis may also affect other organs of the body, including the skin, eyes, lungs, and heart.
a molecule consisting of a five-carbon sugar (ribose), a nitrogen-containing base, and one or more phosphate groups.
often the result of vitamin D deficiency. Rickets affects children while their bones are still growing. It is characterized by soft and deformed bones and is the result of an impaired incorporation of calcium and phosphate into the skeleton.
the probability of a negative outcome occurring.
ribonucleic acid; a single-stranded nucleic acid composed of many nucleotides. The nucleotides in RNA are composed of a nitrogen-containing base (adenine, guanine, cytosine, or uracil), a five-carbon sugar (ribose) and a phosphate group. RNA functions in the translation of the genetic information encoded in DNA to proteins.
the first part of the stomach of a ruminant.
an animal that chews cud. Ruminant animals include cattle, goats, sheep, and deer.

Glossary: S

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a state of fullness.
Saturated fatty acid
a fatty acid with no double bonds between carbon atoms.
Scavenge (free radicals)
to combine readily with free radicals, preventing them from reacting with other molecules.
a debilitating brain disorder that affects about 1% of the world’s population. Symptoms may include hallucinations, delusions, thought disorders, disorders of movement, cognitive deficits, lack of emotional expression, or impaired ability to speak, plan, and interact with others. Although its cause is not known, schizophrenia is thought to result from a combination of genetic and environmental factors.
a disorder caused by lack of vitamin C. Symptoms include anemia, bleeding gums, tooth loss, joint pain, and fatigue. Scurvy is treated by supplying foods high in vitamin C, as well as with vitamin C supplements.
Sebaceous gland
gland found at the base of hair follicles that secretes sebum.
a sebum-producing cell in the skin.
a waxy/oily substance secreted by mammals that coats the outer layer of the skin.
uncontrolled electrical activity in the brain, which may produce a physical convulsion, minor physical signs, thought disturbances, or a combination of symptoms.
Senile plaque
plaques made by deposits of β-amyloid peptides in Alzheimer's disease.
5-hydroxytryptamine. Serotonin is a neurotransmitter that may also function as a vasoconstrictor (substance that causes blood vessels to narrow).
whole blood without clotting factors. Serum is separated from blood cells using a centrifuge. Unlike plasma, serum lacks clotting factors because it is obtained from blood that has been allowed to clot.
Short bowel syndrome
a malabsorption syndrome resulting from the surgical removal of an extensive portion of the small intestine.
Sickle cell anemia
a hereditary disease in which a mutation in the gene for one of the proteins that comprises hemoglobin results in the formation of defective hemoglobin molecules known as hemoglobin S. Individuals who are homozygous for this mutation (possess two genes for hemoglobin S) have red blood cells that change from the normal discoid shape to a sickle shape when the oxygen supply is low. These sickle-shaped cells are easily trapped in capillaries and damaged, resulting in severe anemia. Individuals who are heterozygous for the mutation (possess one gene for hemoglobin S and one normal hemoglobin gene) have increased resistance to malaria.
Sideroblastic anemia
a group of anemias that are all characterized by the accumulation of iron deposits in the mitochondria of immature red blood cells. These abnormal red blood cells do not mature normally, and many are destroyed in the bone marrow before reaching the circulation. Sideroblastic anemias can be hereditary, idiopathic (unknown cause), or caused by such diverse factors as certain drugs, alcohol, or copper deficiency.
Signal transduction pathway
a cascade of events that allows a signal outside a cell to result in a functional change inside the cell. Signal transduction pathways play important roles in regulating numerous cellular functions in response to changes in a cell’s environment.
Sleep apnea
a sleep disorder characterized by repeated cessation of breathing.
Small intestine
the part of the digestive tract that extends from the stomach to the large intestine. The small intestine includes the duodenum (closest to the stomach), the jejunum, and the ileum (closest to the large intestine).
capable of being dissolved.
the polyol (sugar alcohol) corresponding to glucose.
the formation and development of mature spermatozoa.
the mature male reproductive cell.
Spina bifida
a birth defect, also known as a neural tube defect, resulting from failure of the lower end of the neural tube to close during embryonic development. Spina bifida, the most common cause of infantile paralysis, is characterized by a lack of protection of the spinal cord by its membranes and vertebral bones.
intercellular edema in the epidermis.
also known as celiac sprue and celiac disease, it is an inherited disease in which the intestinal lining is inflamed in response to the ingestion of a protein known as gluten. Treatment of celiac disease involves the avoidance of gluten, which is present in many grains, including wheat, rye, oats, and barley. Inflammation and atrophy of the lining of the small intestine leads to impaired nutrient absorption.
a drug that inhibits the enzyme, 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase, thus decreasing endogenous synthesis of cholesterol and lowering blood cholesterol concentrations.
the state of nutrition of an individual with respect to a specific nutrient. Diminished or low status indicates inadequate supply or stores of a specific nutrient for optimal physiological functioning.
the accumulation of fat in the liver.
obstruction or narrowing of a passage. Coronary stenosis refers specifically to obstruction or narrowing of a coronary artery, which supplies blood to the heart muscle (myocardium).
a molecule related to cholesterol. Many important hormones, such as estrogen and testosterone, are steroids.
Steroid hormone receptor
a protein within a cell which binds to a specific steroid hormone. Binding of the steroid hormone changes the shape of the receptor protein and activates it, allowing it to activate gene transcription. In this way, a steroid hormone can activate the synthesis of specific proteins.
Stratum corneum
the outer layer of skin; consists of corneocytes that are connected by various proteins and lipids to form a tight barrier around underlying tissue.
Stress fracture
a hairline or microscopic break in a bone, usually due to repetitive stress rather than trauma. Stress fractures are usually painful, and may be undetectable by X-ray. Although they may occur in almost any bone, common sites of stress fractures are the tibia (lower leg) and metatarsals (foot). 
damage that occurs to a part of the brain when its blood supply is suddenly interrupted (ischemic stroke) or when a blood vessel ruptures and bleeds into the brain (hemorrhagic stroke). A stroke is also called a cerebrovascular accident (CVA).
without clinical signs or symptoms; sometimes used to describe the early stage of a disease or condition, before symptoms are detectable by clinical examination or laboratory tests.
under the skin.
a reactant in an enzyme-catalyzed reaction.
a disaccharide composed of two monosaccharides: glucose and fructose. Also known as cane sugar or table sugar.
a nutrient or phytochemical supplied in addition to that which is obtained in the diet.
cell-cell junction that allows chemical or electrical signals to be passed from a neuron to another neuron or muscle cell.
Synaptic plasticity
the ability of neurons to change the number or strength of their synaptic connections. Synaptic plasticity is believed to underlie the processes of learning and memory.
a combination of symptoms that occur together and is indicative of a specific condition or disease.
when the effect of two treatments together is greater than the sum of the effects of the two individual treatments, the effect is said to be synergistic.
the formation of a chemical compound from its elements or precursor compounds.
Systematic review
a structured review of the literature designed to answer a clearly formulated question. Systematic reviews use systematic and explicitly predetermined methods to identify, select and critically evaluate research relevant to the question, and to collect and analyze data from the studies that are included in the review. Statistical methods, such as meta-analysis, may be used to summarize the results of the included studies.
Systemic lupus erythematosus (SLE)
a chronic autoimmune disease characterized by inflammation of the connective tissue. SLE is more common in women than men and may result in inflammation and damage to the skin, joints, blood vessels, lungs, heart, and kidneys.
Systolic blood pressure
the highest arterial pressure measured during the heart beat cycle, and the first number in a blood pressure reading (e.g., 120/80).

Glossary: T

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any of a large group of plant-derived compounds. Tannins tend to be bitter tasting and may function in pigment formation and plant protection. 
broken capillaries in the skin.
the segment of DNA at each end of a chromosome.
an agent that interferes with normal development of an embryo or fetus.
one-third of a sample or population.
a condition of prolonged and painful spasms of the voluntary muscles, especially the fingers and toes (carpopedal spasm), as well as the facial musculature.
Thalassemia major
Beta thalassemia is a genetic disorder that results in abnormalities of the globin (protein) portion of hemoglobin. An individual who is homozygous for the β thalassemia gene (has two copies of the β thalassemia gene) is said to have thalassemia major. Infants born with thalassemia major develop severe anemia a few months after birth, accompanied by pallor, fatigue, poor growth, and frequent infections. Blood transfusions are used to treat thalassemia major but cannot cure it. 
Thalassemia minor
Individuals who are heterozygous for the β thalassemia gene (carry one copy of the β thalassemia gene) are said to have thalassemia minor or thalassemia trait. These individuals are generally healthy but can pass the β thalassemia gene to their children and are said to be carriers of the β thalassemia gene.
the process of controlling body temperature to prevent both excessive cooling and warming.
the point at which a physiological effect begins to be produced, for example, the degree of stimulation of a nerve which produces a response or the level of a chemical in the diet that results in a disease.
a butterfly-shaped gland in the neck that secretes thyroid hormones. Thyroid hormones regulate a number of physiologic processes, including growth, development, metabolism, and reproductive function.
Thyroid follicular cancer
a cancer of the thyroid gland that constitutes about 30% of all thyroid cancers. It has a greater rate of recurrence and metastases (spreading to other organs) than thyroid papillary cancer.
Thyroid papillary cancer
the most common form of thyroid cancer, which most often affects women of childbearing age. Thyroid papillary cancer has a lower rate of recurrence and metastases (spreading to other organs) than thyroid follicular cancer.
applied to the skin or other body surface.
Total Parenteral Nutrition (TPN)
intravenous (I.V.) feeding that provides patients with essential nutrients when they are too ill to eat normally.
a condition caused by poisoning.
Trabecular bone
also known as spongy or cancellous bone, the type of bone found within the ends of long bones and inside flat bones and spinal vertebrae.
(DNA transcription); the process by which one strand of DNA is copied into a complementary sequence of RNA.
Transcription factor
a protein that functions to initiate, enhance, or inhibit the transcription of a gene. Transcription factors can regulate the formation of a specific protein encoded by a gene. 
Trans fat
hydrogenated or partially hydrogenated oils.
Transient ischemic attack (TIA)
sometimes called a small or mini stroke. TIAs are caused by a temporary disturbance of blood supply to an area of the brain, resulting in a sudden, brief (usually less than one hour) disruptions in certain brain functions.
(RNA translation); the process by which the sequence of nucleotides in a messenger RNA (mRNA) molecule directs the incorporation of amino acids into a protein.
an injury or wound.
trembling or shaking of a part or all of the body.
lipid consisting of three fatty acid molecules bound to a glycerol backbone. Triglycerides are the principal form of fat in the diet, although they are also synthesized endogenously. Triglycerides are stored in adipose tissue and represent the principal storage form of fat. Elevated serum triglycerides are a risk factor for cardiovascular disease.
a hereditary disorder characterized by increased urinary excretion of trimethylamine, a compound with a “fishy” or foul odor.
a clinical measure of bone mineral density (BMD) obtained by dual X-ray absorptiometry (DEXA).
an infection caused by bacteria called mycobacterium tuberculosis. Many people infected with tuberculosis have no symptoms because it is dormant. Once active, tuberculosis may cause damage to the lungs and other organs. Active tuberculosis is also contagious and is spread through inhalation. Treatment of tuberculosis involves taking antibiotics and vitamins for at least six months.
an infectious disease spread by the contamination of food or water supplies with the bacteria called salmonella typhi. Food and water can be contaminated directly by sewage or indirectly by flies or poor hygiene. Though rare in the US, it is common in some parts of the world. Symptoms include fever, abdominal pain, diarrhea, and a rash. It is treated with antibiotics and intravenous fluids. Vaccination is recommended to those traveling to areas where typhoid is common.

Glossary: U

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tolerable upper intake level. Established by the Food and Nutrition Board of the US Institute of Medicine, the UL is the highest level of daily intake of a specific nutrient likely to pose no risk of adverse health effects in almost all individuals of a specified age.
Ulcerative colitis
a chronic inflammatory disease of the colon and rectum. Symptoms of ulcerative colitis include abdominal pain, cramping, and bloody diarrhea.
a test in which high-frequency sound waves (ultrasound) are bounced off tissues and the echoes are converted into a picture (sonogram).
Unsaturated fatty acid
a fatty acid with at least one double bond between carbons.
an excessive concentration of urea and other nitrogenous waste products in the blood that are normally excreted by the kidneys.
Uric acid
an antioxidant produced by the body.

Glossary: V

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Vascular dementia
dementia resulting from cerebrovascular disease, for example, a cerebrovascular accident (stroke).
Vascular endothelium
the single cell layer that lines the inner surface of blood vessels. Healthy endothelial function promotes vasodilation and inhibits platelet aggregation (clot formation).
the creation of new blood vessels or the extension of existing blood vessels into tissue.
narrowing of a blood vessel.
relaxation or opening of a blood vessel.
the material in which a treatment compound is dissolved.
the two lower chambers of the heart that pump blood to the body (left) and the lungs (right).
of or pertaining to a vertebra, 1 of the 23 bones that comprise the spine.
literally a small bag or pouch. Inside a cell, a vesicle is a small organelle surrounded by its own membrane.
marked by a rapid, severe, or damaging course.
a microorganism, which cannot grow or reproduce apart from a living cell. Viruses invade living cells and use the synthetic processes of infected cells to survive and replicate.
an organic (carbon-containing) compound necessary for normal physiological function that cannot be synthesized in adequate amounts and must therefore be obtained in the diet.
Very-low-density lipoprotein cholesterol. VLDLs transport lipids in the bloodstream.

Glossary: W, X, Y, Z

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a chemical compound that is foreign to the organism. Xenobiotics may include dietary factors, toxins, pharmaceuticals, and pollutants.
Xenobiotic metabolism
a series of enzymatic reactions that convert a foreign chemical compound into an inert substance that can be safely excreted from the body. The three phases of xenobiotic metabolism include: (i) activation, (ii) functionalization, and (iii) efflux.
a transplant of tissue from a donor of one species to a recipient of another species.
Zollinger-Ellison syndrome
a rare disorder caused by a tumor called a gastrinoma, most often occurring in the pancreas. The tumor secretes the hormone gastrin, which causes increased production of gastric acid leading to severe recurrent ulcers of the esophagus, stomach, and the upper portions of the small intestine.

Nutrient Index

Articles on the following nutrients, phytochemicals, food, and beverages are available in the Linus Pauling Institute's Micronutrient Information Center:

Disease Index

Cardiovascular Disease

  • Inflammation (see MIC article)

Relevant Links

US Government Sites

Dietary Reference Intakes (DRI) and Recommended Dietary Allowances (RDA)

Full text versions of the recent reports by the Food and Nutrition Board of the Institute of Medicine on recommended intakes of specific nutrients

Other Health-related Links