Nutrition Research

Summary

Comparison of healthy brain and advanced Alzheimer's

Several nutrients have essential functions in the nervous system, participating in energy metabolism, neurotransmitter synthesis, and antioxidant defense. Patients with Alzheimer’s disease (AD) tend to have low levels of these nutrients in their blood and cerebrospinal fluid (CSF), which is thought to reflect the nutritional status of the brain. It is unclear if this low nutrient status is a consequence of AD progression, poor diet quality associated with cognitive decline, or if it is a causative factor in disease onset and progression. In any case, increased intake of nutrients important for nervous system function is being tested as a strategy to influence the development and symptoms of AD. Overall, nutrient supplementation in AD patients successfully increases nutrient levels in the CSF but has shown no beneficial effects in the clinical course of the disease. For vitamin C, vitamin E, and essential fatty acids, a beneficial effect of nutrient supplementation to prevent or delay the progression of AD may depend on the presence of vascular risk factors, an existing nutrient deficiency, or a certain genetic predisposition.

Disease Overview

Alzheimer’s disease is the most common cause of dementia in older adults. At early stages of Alzheimer’s disease, before symptoms are present, accumulation of abnormal protein deposits (called amyloid plaques) and tangles of fibers (called neurofibrillary tangles) cause nerve cells in the brain to work less efficiently. Over time, affected nerve cells become damaged, completely lose their function, and die. The regions of the brain that they access begin to shrink.

The protein deposits and tangles that characterize Alzheimer’s disease tend to begin in areas of the brain important for learning and memory. Although the rate of progression varies from person to person, damage spreads in a predictable pattern to other regions of the brain, eventually affecting many cognitive, behavioral, and vital body functions.

At this time, there is no cure for Alzheimer's disease. However, scientists are researching ways in which nutrients influence Alzheimer’s disease prevention and treatment. See below for specific information about nutrients and dietary factors relevant to Alzheimer's disease.

DEFINITIONS
Alzheimer’s disease – a disease characterized by abnormal clumping and tangles of proteins in the brain, thus interfering with nerve cell function
Dementia – a loss of cognitive and behavioral abilities to an extent that interferes with daily life
Cognition – the mental process of thought; includes brain functions like attention, memory, planning, developing strategies, and problem solving
Cognitive decline – a general term that describes any loss of cognition; it could refer to a decline in any of the different types of thought processes listed above

Nutrition Research

DEFINITIONS
Test tube (in vitro) experiment - a research experiment performed in a test tube, culture dish, or other artificial environment outside of a living organism; in vitro is a Latin phrase meaning in glass
Animal experiment - a research experiment performed in a laboratory animal; many different animal species are studied in the laboratory, including terrestrial (land), aquatic (water), and microscopic animals
Observational study - a human research study in which no experimental intervention or treatment is applied, and participants are simply observed over time
Randomized controlled trial - a human research study in which participants are assigned by chance alone to receive either an experimental agent (the treatment group) or a placebo (the control group)
Placebo - a chemically inactive substance

 

Essential Fatty Acids

What they do

General

  • Essential fatty acids (EFAs) are a type of polyunsaturated fatty acid that must be obtained from the diet.
  • EFAs are structural components of every cell in the body, are converted to compounds that influence inflammation and immunity, and serve as an important source of energy.

Alzheimer’s-specific

  • The long-chain omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may protect the brain by reducing inflammation, improving blood flow, and reducing abnormal clumping of the protein β-amyloid.
What we know
  • Low levels of DHA are associated with an increased risk of developing Alzheimer’s disease.
  • Diets rich in long-chain omega-3 polyunsaturated fatty acids are associated with a lower risk of cognitive decline.
  • Randomized controlled trials testing the effect of long-chain omega-3 polyunsaturated fatty acids on the symptoms and progression of Alzheimer’s disease have reported mixed results.
    • Overall, the data favor a role for diets rich in long-chain omega-3 polyunsaturated fatty acids (from fatty fish) in slowing cognitive decline but not for omega-3 supplementation in the prevention or treatment of Alzheimer’s disease.
    • A beneficial effect of omega-3 supplements may depend on accompanying conditions, such as the involvement of a vascular issue or having a certain genetic predisposition (the presence of apolipoprotein epsilon 4 [APOE e4]).
HIGHLIGHT
The apolipoprotein E (APOE) gene produces a protein involved in transporting and delivering lipids through the bloodstream. At least three slightly different versions of APOE occur in the population. Those who inherit one particular version of APOE, called apolipoprotein E epsilon 4 (APOE e4), have an increased risk of developing Alzheimer's disease.

For references and more information, see the section on Alzheimer’s disease in the Essential Fatty Acids article.

There are two essential fatty acids: linoleic acid (an omega-6 polyunsaturated fatty acid) and alpha-linolenic acid (an omega-3 polyunsaturated fatty acid). These fatty acids are considered essential nutrients because they cannot be made in the body and must be consumed in the diet. Vegetable oils, especially safflower oil, sunflower oil, and corn oil, are a good source of linoleic acid.Flax and chia sees, walnuts, canola oil, and soybean oil are good sources of alpha-linoleic acid. Inside body tissues, the essential fatty acids are converted to long-chain fatty acids. Due to low efficiency of conversion, it is recommended to obtain eicosapentaenoic acid (EPA) and docosapentaenoic acid (DHA) from additional sources. Oily fish, fish oil supplements, krill oil supplements, and algae oil supplements are good sources of EPA and DHA.

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Choline

What it does

General

  • Humans can synthesize small amounts of choline but not enough to support health. Therefore, choline must be consumed in the diet and is considered an essential nutrient.
  • Choline functions as a vital structural component of cell membranes and some proteins.

Alzheimer’s-specific

  • Alzheimer’s disease has been associated with low levels of the neurotransmitter acetylcholine. Because choline is a precursor to acetylcholine, scientists have tested if choline supplements can increase acetylcholine levels in the brains of Alzheimer’s patients.
What we know
  • Overall, randomized controlled trials that tested supplementation with large doses of lecithin (a source of choline) have shown no effect of lecithin on measures of cognitive function in Alzheimer’s patients.

For references and more information, see the section on Neurodegenerative diseases in the Choline article.

Choline Flashcard. Main Functions: 1) structural component of all cell membranes, 2) transport and metabolism of fat and cholesterol, 3) helps make some important neurotransmitters, and 4) helps maintain normal levels of homocysteine in the blood. Good sources: egg (1 large), 147 mg; meat (beef and poultry), beef (3 ounces), 97 mg; seafood (fish and shellfish), scallop (steamed, 3 ounces) 94 mg (mg=milligrams; a three-ounce serving of meat or fish is about the size of a deck of cards; Daily Recommnedation: 550 mg for all men and 425 mg for all women; Special Notes: 1) Choline can be made in the body, but it is not enough to support health. Therefore, it must also be consumed in the diet. 2) A varied diet should provide enough choline for most people, but strict vegetarians who don't consume milk or eggs may be at risk of inadequate choline intake.

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Copper

What it does

General

  • Copper is an essential trace mineral that assists in energy production, iron utilization, antioxidant defense, and the synthesis of neurotransmitters and connective tissue.

Alzheimer’s-specific

  • Copper is normally bound to proteins in the blood; high levels of unbound copper have been found in Alzheimer’s patients.
  • Exposure to high levels of unbound copper may contribute to metal accumulation in sensitive areas of the brain, oxidative stress, plaque formation, and damage to nervous tissue.
What we know
  • Observational studies suggest that a diet that is high in both copper and saturated fat may foster cognitive decline in elderly subjects.
  • The role of copper in the development and progression of Alzheimer’s disease is unclear at this time; there is evidence that either copper supplementation or administration of copper-binding agents could stabilize some features of Alzheimer’s disease.
  • The complicated relationship between copper and Alzheimer’s disease is an area of active research.

For references and more information, see the section on Neurodegenerative diseases in the Copper article.

 

Copper Flashcard. Main Functions: 1) frees iron from storage so it can be used to make red blood cells, 2) assists antioxidant enzymes, and 3) assists in the formation and maintenance of connective tissue. Good Sources: shellfish (oysters, clams, crab), oysters, 6 medium = 2,397 micrograms; nuts (hazelnuts, almonds), cashew nuts, raw, 1 ounce or 18 cashews = 622 micograms; legumes (beans, peas, lentils), lentils (cooked), 1 cup=497 micrograms; Daily Recommendation: 900 micrograms for all adults; Special Notes: 1) Liver (from lamb, veal, beef, and geese) is also a rich source of copper. 2) Copper is widely distributed in food; a varied diet should provide enough copper to meet the daily recommendation. 3) Copper toxicity is rare. The Tolerable Upper Intake Level (UL) for adults is 10,000 micrograms/day from food and supplements.

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Folate

What it does

General

  • Folate is a B-vitamin required for DNA synthesis and the formation of new cells. Folate therefore supports the growth and repair of all tissues in the body, including nerve and brain tissue.
  • Additionally, the B-vitamins folate, vitamin B12, and vitamin B6 work together to convert homocysteine to methionine, an amino acid used in countless essential cellular activities.

Alzheimer’s-specific

  • Folate deficiency may lead to decreased synthesis of methionine and the accumulation of homocysteine. Too much homocysteine in the blood is associated with an increased risk of developing Alzheimer’s disease.
What we know
  • Long-term folate deficiency is associated with an increased risk of developing Alzheimer’s disease.
  • Although folic acid supplementation improves folate status and lowers blood homocysteine levels, randomized controlled trials have not demonstrated a beneficial effect of folic acid supplementation on symptoms or progression of Alzheimer’s disease.

For references and more information, see the section on Alzheimer’s disease and cognitive impairment in the Folate article.

Additional reference

  • Hinterberger M and Fischer P. Folate and Alzheimer: when time matters. Journal of Neural Transmission. 2013;120:211-224

Folate Flashcard. Main Functions: 1) required for DNA synthesis, 2) supports cell growth and repair, 3) helps prevent neural tube defects. Good Sources: legumes (beans, peas, lentils), lentils (cooked) one-half cup = 179 micrograms dietary folate equivalents (DFE); green leafy vegetables (kale, spinach), spinach (cooked) one-half cup, 131 micrograms DFE; fortified food and supplements, sliced bread (enriched), 1 slice, 84 micrograms DFE. Daily Recommendation: 400 micrograms DFE for adults, 600 micrograms DFE for pregnant women. Special Notes: 1) Folate is a general term that refers to both natural folates in food and folic acid, the synthetic form used in supplements and fortified food. 2) DFE = a unit of measure that accounts for differences in the absorption of naturally occurring food folate and synthetic folic acid. 3) To reduce the risk of neural tube defects, all women capable of becoming pregnant should consume 400 micrograms of folic acid daily in addition to the folate obtained from a varied diet. 4) Very high-dose folic acid supplementation (5,000 micrograms) can mask a vitamin B12 deficiency, specifically signs of nerve damage.

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Iron

What it does

General

  • Iron, an essential trace mineral, is required for the synthesis of hundreds of vital molecules, facilitates oxygen transport and storage, and assists antioxidant enzymes.

Alzheimer’s-specific

  • Abnormal iron accumulation and accompanying oxidative injury in the brain may contribute to the development of a number of neurodegenerative diseases, including Alzheimer's disease.
What we know
  • The abnormal accumulation of iron in the brain does not appear to be a result of increased dietary iron, but rather, a disruption in the complex process of cellular iron regulation.
HIGHLIGHT
Although dietary iron consumption does not influence the development of Alzheimer’s disease, the requirement for iron goes down with age. The recommended dietary allowance (RDA) for men ≥19 years of age and women ≥51 years of age is 8 milligrams (mg) per day. It is recommended that men and postmenopausal women avoid dietary supplements containing iron.

For references and more information, see the section on Iron overload in the Iron article.

Iron Flashcard. Main Functions: 1) Helps make healthy red blood cells that transport oxygen throughout the body, 2) Critical for normal immune function, 3) Structural component of hundreds of essential molecules, and 4) Assists antioxidant enzymes. Good Sources: There are two forms of dietary iron: heme iron and nonheme iron. Heme iron is found in red meat, poultry, and fish. 3 ounces of red meat contains 2.3 mg of heme iron. Nonheme iron is found in lentils, vegetables, and fortified food. One-half cup of cooked lentils contains 3.3 mg of nonheme iron. Daily Recommendation: 8 mg for adult men, 18 mg for women 19-50 years, 8 mg for women 51 years and older. Special Notes: 1) Heme iron is better absorbed than nonheme iron; the absorption of nonheme iron is enhanced by vitamin C. 2) National dietary surveys indicate that iron is underconsumed by adolescent and premenopausal females. 3) The Daily Recommendation for iron is significantly increased during pregnancy (from 18 to 27 mg/day), yet dietary surveys indicate that the average intake among pregnant women in the US is 15 mg/day. 4) Iron is efficiently recycled by the body. Premenopausal women have higher requirements due to menstrual losses.

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Thiamin

What it does

General

  • Thiamin is a B-vitamin that helps convert food into useable energy.
  • More specifically, thiamin functions as an essential assistant to enzymes involved in glucose and amino acid metabolism.

Alzheimer’s-specific

  • Nerve tissue relies heavily on glucose as a fuel source. Thiamin deficiency compromises glucose metabolism in nerve cells, which can contribute to nerve cell death in certain vulnerable regions of the brain. Scientists are therefore investigating if thiamin deficiency is also connected to Alzheimer’s disease.
What we know
  • Test tube and animal experiments indicate that thiamin deficiency increases β-amyloid production and plaque formation, which are subsequently reversed following thiamin supplementation.
  • A limited number of observational studies in humans show that thiamin status and thiamin-dependent enzymatic activity is reduced in individuals with Alzheimer’s disease.
  • Randomized controlled trials of thiamin supplementation in Alzheimer’s patients found no evidence that thiamin was a useful treatment for symptoms of Alzheimer's disease.

For references and more information, see the section on Alzheimer’s disease in the Thiamin article.

Thiamin Flashcard. Main Functions: (1) helps covert food into usebale energy, and (2) assists enzymes involved in glucose and amino acid metabolism. Good Sources: Legumes (beans, peas, lentils), lentils (cooked), one-half cup=0.01 mg; Whole Grains (wheat, oats, barley), brown rice, 1 cup=0.19 mg; pork products (ham, pork), lean pork, 3 ounces=0.81 mg. Daily Recommendation. 1.2 mg/day for men and 1.1 mg/day for women. Special Notes. (1) In the US, thiamin is sometimes added back to refined grains, a process called fortification. (2) Thus, enriched rice, bread, breakfast cereal, and energy bars are also a source of thiamin.

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Vitamin B6

What it does

General

  • Vitamin B6 helps convert food into useable energy and assists in the formation of neurotransmitters, red blood cells, and building blocks of DNA.
  • Additionally, the B-vitamins folate, vitamin B12, and vitamin B6 work together to maintain normal levels of homocysteine.

Alzheimer’s-specific

  • Vitamin B6 deficiency may lead to the accumulation of homocysteine. Too much homocysteine in the blood is associated with an increased risk of developing Alzheimer’s disease.
What we know
  • Low blood concentrations of vitamin B6, vitamin B12, and folate have been found in Alzheimer’s patients.
  • Although high-dose supplementation with vitamin B6, vitamin B12, and folic acid lowers blood homocysteine concentration, it appears to have no effect on cognitive decline in Alzheimer’s patients.

For references and more information, see the section on Cognitive decline and Alzheimer’s disease in the Vitamin B6 article.

Vitamin B6 Flashcard. Main Functions: 1) helps convert food into energy, 2) helps make red blood cells, 3) helps maintain normal levels of homocysteine in the blood. Good Sources: Fish (slamon, tuna, halibut), wild salmon, 3 ounces, 0.5-0.8 mg; poultry (turkey, chicken, duck), light-meat turkey (cooked), 3 ounces = 0.7 mg; nuts (hazelnuts, walnuts) pistachio nuts, 1 ounce or 47 pistachios = 0.5 mg. Daily Recommendation: 2 mg for all adults. Special Notes: 1) The Daily Recommendation listed is specific to the LPI based on extensive review of the scientific evidence. The Institute of Medicine's Recommended Dietary Allowance (RDA) is 1.3 mg/day for adults 19-50 years, 1.7 mg/day for men 51 years and older, and 1.5 mg/day for women 51 years and older. 2) In the US, vitamin B6 is added back to refined grains. Therefore, enriched products are also a source of vitamin B6. 3) Excessive supplementation of vitamin B6 (more than 100 mg/day) can cause nerve damage and skin lesions.

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Vitamin B12

What it does

General

  • Vitamin B12 helps convert food into useable energy, helps make red blood cells, and is required for proper nerve function.
  • Additionally, the B-vitamins folate, vitamin B12, and vitamin B6 work together to maintain normal levels of homocysteine.

Alzheimer’s-specific

  • Vitamin B12 deficiency may lead to the accumulation of homocysteine. Too much homocysteine in the blood is associated with an increased risk of developing Alzheimer’s disease.
What we know
  • Low concentrations of vitamin B12 in the blood and cerebrospinal fluid (CSF) have been found in patients with Alzheimer's disease.
  • There is some evidence that vitamin B12 supplementation reduces the rate of atrophy in regions of the brain affected by Alzheimer’s disease. However, brain atrophy also occurs with normal aging and other types of dementia, thus it is unclear if vitamin B12 supplementation will influence the development of Alzheimer’s disease specifically.
  • Although high-dose supplementation with vitamin B6, vitamin B12, and folic acid lowers homocysteine concentration in the blood and CSF, it appears to have no effect on cognitive decline in Alzheimer’s patients.

For references and more information, see the section on Cognitive decline, dementia, and Alzheimer’s disease in the Vitamin B12 article.

Vitamin B12 (cobalamin) Flashcard. Main Functions: 1) Helps make red blood cells, 2) Required for proper nerve function, and 3) Helps maintain normal levels of homocysteine in the blood. Good Sources: Vitamin B12 is only found in animal products. Seafood (shellfish, fish), clams (steamed) 3 ounces = 84 micrograms; poultry (turkey, chicken, duck), roasted turkey, 3 ounces = 0.8 micrograms; red meat (beef, pork, lamb), lean beef plate steak (grilled), 3 ounces = 6.9 micrograms. Daily Recommendation: adults 19-50 years = 2.4 micrograms; LPI recommends older adults (51 years and older) take 100-400 micrograms of supplemental vitamin B12. Special Notes: 1) Over-the-counter antacids reduce vitamin B12 absorption. 2) The capacity to absorb vitamin B12 from food goes down with age. 3) Symptoms of vitamin B12 deficiency include tingling and numbness in the extremities, nerve damage, and memory loss. 4) Older adults and individuals consuming a vegan diet should obtain vitamin B12 from supplements or fortified food.

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Vitamin C

What it does

General

  • Vitamin C (ascorbic acid) neutralizes a variety of reactive oxygen species, recycles important cellular antioxidants, enhances the activity of immune cells, and helps make collagen, carnitine, and several neurotransmitters.

Alzheimer’s-specific

  • Oxidative stress is thought to be an early causative event in the onset of various neurodegenerative diseases, including Alzheimer’s disease. Therefore, ensuring adequate antioxidant defense is being investigated as a strategy to reduce the risk of Alzheimer’s disease onset and progression.
What we know
  • Vitamin C is concentrated in the brain, but the ways in which it affects cognitive function and decline are not yet known.
  • Studies in animal models of Alzheimer’s disease suggest that vitamin C administration may delay amyloid plaque formation.
  • Higher plasma vitamin C levels are generally associated with better cognitive function and lower risk of cognitive decline.
  • The few, small randomized controlled trials that tested vitamin C supplementation (given in conjunction with other antioxidants or medications) in Alzheimer’s patients report an increase in vitamin C levels and decrease in oxidative stress in the CSF, but no beneficial effect on the clinical course of Alzheimer’s disease.
  • Benefits from vitamin C supplementation may depend on the presence of vascular risk factors or an existing vitamin C deficiency.
DEFINITIONS
Reactive oxygen species (ROS) - highly unstable oxygen-containing compounds that react easily with nearby cellular structures, potentially causing damage
Oxidative stress - a situation in which the production of reactive oxygen species exceeds the ability of an organism to eliminate or neutralize them
Antioxidants - compounds that prevent or repair the damage caused by reactive oxygen species

For references and more information, see the section on Alzheimer’s disease in the Vitamin C article.

Vitamin C (ascorbic acid) Flashcard. Main Functions: 1) Antioxidant defense, 2) Enhances immune function, 3) Needed to make collagen, carnitine, and the neurotransmitters serotonin and norepinephrine. Good Sources: Fruit, 1 medium-sized kiwifruit = 90 mg; strawberries, 1 cup whole, 85 mg; Vegetables (broccoli, kale, tomatoes), sweet red pepper (one-half cup, chopped) = 95 mg. Daily Recommendation is 400 mg for all adults. Special Notes: 1) Heat destroys vitamin C. Try to eat fresh foods and cook by steaming, microwaving, or stir-frying. 2) Vitamin C in food is identical to vitamin C in supplements. 3) The Daily Recommendation listed is specific to the LPI based on extensive review of the scientific evidence. The Institute of Medicine's Recommended Dietary Allowance (RDA) is 90 mg/day for men and 75 mg/day for women.

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Vitamin E

What it does

General

  • Vitamin E functions as an antioxidant in lipid (fat) environments and enhances the activity of immune cells.

Alzheimer’s-specific

  • Vitamin E is an important antioxidant nutrient in the brain, where it functions to protect nerve and brain tissue from oxidative damage.
What we know
  • Some studies have found low concentrations of vitamin E in the cerebrospinal fluid of patients with Alzheimer's disease.
  • Randomized controlled trials have reported mixed results. While one study found that high-dose supplementation of vitamin E (2,000 IU [800 mg] of RRR-α-tocopherol per day) reduced cognitive decline in Alzheimer’s patients, another similar study found no effect.
DEFINITIONS
Antioxidants - compounds that prevent or repair the damage caused by reactive oxygen species.
Reactive oxygen species (ROS) - highly unstable oxygen-containing compounds that react easily with nearby cellular structures, potentially causing damage.
Oxidative damage - damage that arises when the production of reactive oxygen species exceeds the ability of an organism to eliminate or neutralize them.

For references and more information, see the section on Cognitive deterioration and Alzheimer’s disease in the Vitamin E article.

Vitamin E (alpha-tocopherol) Flashcard. Main Functions: 1) Boosts antioxidant defense, 2) Protects cell membranes, and 3) Enhances immune function. Good Sources: vegetable oil, sunflower oil (1 tablespoon), 5.6 mg; nuts (hazelnuts, peanuts), almonds, 1 ounce or 23 almonds, 7.3 mg; avocado, 1 medium-sized, 2.7 mg. Daily Recommendation is 15 mg for all adults. Special Notes: 1) The term "vitamin E" actually refers to a family of eight coupounds. Alpha-tocopherol is the most active vitamin E compound. 2) More than 90% of Americans do not meet the dietary requirement for vitmain E. 3) Synthetic vitamin E (in supplements and fortified food) is less bioavailable than naturally occurring vitamin E from food.

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L-Carnitine

What it does

General

  • L-Carnitine can be synthesized in the body and obtained from food and dietary supplements. It is considered a conditionally essential nutrient because in some situations, the body’s demand for L-carnitine exceeds its capacity to synthesize it.
  • L-carnitine helps the body convert lipids (fats) into useable energy.

Alzheimer’s-specific

  • The acetyl and carnitine components of acetyl-L-carnitine (ALCAR) have been shown to influence energy metabolism, protein stability and clumping, and nerve transmission in the brain.
What we know
  • Overall, randomized controlled trials on the effect of ALCAR supplementation on the symptoms and progression of Alzheimer’s disease have reported mixed results: either no effect or a small beneficial effect.
  • ALCAR may slow cognitive decline in certain subgroups of Alzheimer’s patients, for example, in patients 65 years of age or younger or in those with a certain genetic predisposition (the presence of apolipoprotein E epsilon 4 [APOE e4]). Research is ongoing.
HIGHLIGHT
The apolipoprotein E (APOE) gene produces a protein involved in transporting and delivering lipids through the bloodstream. At least three slightly different versions of APOE occur in the population. Those who inherit one particular version of APOE, called apolipoprotein E epsilon 4 (APOE e4), have an increased risk of developing Alzheimer’s disease.

For references and more information, see the section on Alzheimer’s disease (dementia) in the L-Carnitine article.

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Curcumin

What it does

General

  • Curcumin is a naturally occurring plant chemical that is abundant in the spice turmeric. Experiments performed in test tubes indicate that curcumin can induce antioxidant, anti-inflammatory, and cellular defense systems.

Alzheimer’s-specific

  • Test tube experiments indicate that curcumin can inhibit abnormal clumping of a protein called β-amyloid, an early feature of Alzheimer’s disease.
  • Animal experiments indicate that dietary curcumin can decrease oxidative stress, inflammation, clumping of β-amyloid, and memory loss.
HIGHLIGHT
Test tube experiments are performed on isolated cells, grown in a laboratory, that are exposed to high concentrations of a test compound. It is important to keep in mind that test tube and animal experiments provide valuable information but differ from human trials in many ways. The outcome may differ for humans ingesting dietary or supplemental versions of the experimental agent.
What we know
  • Although there is little evidence from human studies, one six-month long randomized controlled trial in Alzheimer’s patients showed that curcumin had no effect on cognitive performance or inflammatory biomarkers compared to placebo.
  • A lack of clinical effect may be due to the low bioavailability of oral curcumin. In other words, due to break-down by the gastrointestinal tract and liver, very little dietary curcumin reaches nerve cells in the brain.
DEFINITION
Bioavailability - the fraction of ingested compound that reaches the circulation and is transported to the site of action

For references and more information, see the section on Alzheimer’s disease in the Curcumin article.

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Alcoholic Beverages

What they do

General

  • Alcoholic beverages contain ethanol and other ingredients with bioactive properties that may benefit health.
  • When consumed in moderation (no more than two drinks/day for men and one drink/day for women), alcoholic beverages have been associated with beneficial effects in the cardiovascular system.

Alzheimer’s-specific

  • There is some overlap in the neurological systems affected by ethanol and Alzheimer’s disease. Both lead to a reduction in levels of the neurotransmitter acetylcholine as well as the receptors that bind and mediate its important actions.
What we know
  • Alcoholism and heavy alcohol consumption (more than three to four drinks/day) increase the risk of cognitive impairment and dementia.
  • Light-to-moderate alcohol consumption in older adults may be associated with a decreased risk of dementia and Alzheimer’s disease when compared to abstention.
  • There is some evidence that genetic predisposition (the presence of apolipoprotein E epsilon 4 [APOE e4]) modifies the effect of moderate alcohol consumption on the risk of dementia and Alzheimer’s disease. However, it is unclear at this time if APOE e4 helps or hinders the association between alcohol and Alzheimer’s disease; research is ongoing.
HIGHLIGHT
The apolipoprotein E (APOE) gene produces a protein involved in transporting and delivering lipids through the bloodstream. At least three slightly different versions of APOE occur in the population. Those who inherit one particular version of APOE, called apolipoprotein E epsilon 4 (APOE e4), have an increased risk of developing Alzheimer’s disease.

For references and more information, see the section on Cognitive decline, dementia, and Alzheimer’s disease in the Alcoholic Beverages article.

Additional references

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