Nutrition Research

overview of a heart and coronary artery showing damage (dead heart muscle) caused by a heart attack. Also shown is a cross-section of the coronary artery with plaque buildup and a blood clot.Summary

Coronary Heart Disease (CHD) is a leading cause of heart attack and death worldwide. Consumption of nuts, legumes, phytosterols, whole grains, moderate amounts of alcoholic beverages, food rich in long-chain omega-3 polyunsaturated fatty acids, magnesium, vitamin C, fiber, and flavonoids has been associated with a reduced risk of CHD. Additionally, there is some evidence that essential fatty acids may affect the reoccurrence of heart attack in patients with established CHD. Strategies to prevent or slow the progression of endothelial dysfunction and atherosclerosis may help prevent the development of CHD.

Disease Overview

Coronary heart disease (CHD) results from coronary artery disease (CAD) — atherosclerosis inside the small blood vessels that supply blood to the heart. Although CHD technically follows coronary artery disease (CAD), the two terms are often used interchangeably.

CHD is a leading cause of heart attack and death in both men and women in the US and worldwide. A heart attack can occur during CHD when: (1) a plaque in a coronary artery is so large that it blocks blood flow to the heart, or (2) an unstable plaque ruptures and a piece of plaque or resulting blood clot blocks the flow of blood to the heart. Sudden cardiac death (SCD), the result of a fatal arrhythmia, is also a major cause of death in individuals with CHD.

See below for specific information about nutrients and dietary factors relevant to coronary heart disease.

DEFINITIONS
Coronary - referring to the heart and especially the vessels that supply blood to the heart
Atherosclerosis - the buildup of plaque inside arterial walls
Plaque - a deposit of fat, cholesterol, immune cells, fibrin (a blood clotting protein), and other substances that forms inside arterial walls; over time, plaque increases in size, hardens, and can obstruct blood flow through an artery

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 are a type of polyunsaturated fatty acid (PUFA). PUFAs have several double bonds in their structure that give them complex shapes and influence their function.
  • Essential fatty acids 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.
  • There are two classes of essential fatty acids: omega-6 PUFA and omega-3 PUFA.

Coronary Heart Disease (CHD)-specific

  • The omega-6 PUFA, linoleic acid, is the most effective essential fatty acid for reducing blood cholesterol concentration.
  • The major cause of death in CHD is sudden cardiac death (SCD), the result of a fatal arrhythmia. Omega-3 PUFA exert anti-arrhythmic effects in heart muscle cells and may therefore help to prevent fatal arrhythmias that lead to SCD.
What we know
  • Replacing saturated fat with a mixture of omega-6 and omega-3 PUFA (from both plant and marine sources) is associated with a significant reduction in CHD risk.
  • Fish and other seafood are the main food sources of long-chain omega-3 PUFA. Consumption of even one serving of fish per week is associated with a lower risk of fatal CHD; consumption of two to four servings per week is associated with an even lower risk.
  • Findings from observational studies and randomized controlled trials consistently indicate that consumption of fish or fish oil significantly reduces CHD mortality, including fatal myocardial infarction and sudden cardiac death.
    • This beneficial effect is achieved at modest levels of omega-3 PUFA intake.
    • The recommendation is to obtain at least 250 milligrams (mg)/day of EPA plus DHA, preferably by eating at least two servings of oily fish per week
  • Although diets rich in omega-6 PUFA are cardioprotective, supplementation with concentrated sources of the omega-6 PUFA, linoleic acid, may have adverse effects in individuals with pre-existing heart conditions.

For references and more information, see the section on cardiovascular 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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Fiber

What it does

General

  • Fiber is a general term for carbohydrates that are resistant to digestion by human enzymes.
  • Fiber is considered an essential nutrient; it can be obtained from food, additives, and dietary supplements.
  • As fiber travels through the digestive tract, its physical properties (which vary depending on the type of fiber ingested) impart different health effects.
  • Beneficial health effects associated with fiber consumption include: satiety, gastrointestinal health, colonic health, and cardiovascular health.

Coronary Heart Disease (CHD)-specific

  • Fiber may benefit cardiovascular health by decreasing serum cholesterol and by influencing blood glucose and the insulin response.
  • Additionally, fiber-rich foods may provide other nutrients, such as magnesium and potassium, that benefit the cardiovascular system by helping to reduce blood pressure.
What we know
  • Observational studies consistently find that high intakes of fiber-rich foods are associated with a significant reduction in CHD risk and cardiovascular-related mortality.

For references and more information, see the section cardiovascular disease in the Fiber article

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Iron

What it does

General

  • Iron, an essential mineral, is required for the synthesis of hundreds of essential molecules, facilitates oxygen transport and storage, and assists antioxidant enzymes.
  • Iron is transported in the blood inside a protein called transferrin.
  • Dietary iron is found in two forms: heme and non-heme iron. Heme iron comes mainly from meat, poultry, and seafood. Non-heme iron is found in plants, dairy products, meat, fortified food, and dietary supplements.

Coronary Heart Disease (CHD)-specific

  • Animal studies suggest a role for iron-induced oxidative stress in the development of atherosclerosis. However, the role of iron in cardiovascular disease in humans is not yet known.
What we know
  • High dietary intake of heme iron has been associated with an increased risk of CHD. Heme iron consumption is often associated with red meat consumption; thus, it is unclear if heme iron itself or other factors that accompany its intake are responsible for the increased risk of CHD.
  • Observational studies have found that higher transferrin saturation (a measure of circulating iron available for tissue distribution) is associated with a reduced risk of CHD. However, blood markers of iron status are influenced by inflammation and other disease states, thus the relationship between transferrin saturation and CHD risk requires further clarification.

For references and more information, see the section on cardiovascular disease 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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Magnesium

What it does

General

  • Magnesium is an essential mineral that serves as a structural component of the skeleton; assists in hundreds of enzymatic reactions involved in the synthesis of energy, DNA, and proteins; and is required for proper nerve conduction and muscle contraction.

Coronary Heart Disease (CHD)-specific

  • Hypertension is a major risk factor for the development of atherosclerosis and CHD. Higher dietary intake of magnesium is associated with lower blood pressure.
What we know
  • Several large, observational studies indicate that higher dietary intake of magnesium is associated with a reduced risk of CHD.

For references and more information, see the section on cardiovascular disease in the Magnesium article

Magnesium Flashcard. Main Functions: 1) Structural component of bones and teeth, 2) Regulates nerve transmission and muscle contraction, and 3) Assists in hundreds of essential cellular reactions. Good Sources: Whole Grains (wheat, oats, barley), brown rice, cooked, 1 cup = 86 mg; Green Leafy Vegetables (Swiss chard, spinach), spinach (boiled), 1 cup = 157 mg; Nuts (hazelnuts, cashews), almonds, 1 ounce or 23 almonds = 77 mg. Daily Recommendation: 400 mg for men 19-30 years, 420 mg for men 31 years and older; 310 mg for women 19-30 years, 320 mg for women 31 years and older. Special Notes: 1) Most people consume too little magnesium. 2) The Tolerable Upper Intake Level (UL) for magnesium is 350 mg/day from supplements. The UL does not apply to naturally occurring magnesium from food.

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Vitamin C

What it does

General

  • Vitamin C neutralizes a variety of reactive oxygen species, recycles important cellular antioxidants, augments the functional activity of immune cells, and helps make collagen, L-carnitine, and several neurotransmitters.

Coronary Heart Disease (CHD)-specific

What we know
  • The majority of observational studies report an inverse association between vitamin C intake and CHD risk. In other words, the higher the vitamin C intake, the lower the risk of CHD.
  • Overall, the results of observational studies and randomized controlled trials indicate that maximal reduction of CHD risk may require vitamin C intakes of 400 milligrams (mg) or more per day.
DEFINITIONS
Reactive oxygen species (ROS) - highly unstable oxygen-containing compounds that react easily with nearby cellular structures, potentially causing damage
Antioxidants - compounds that prevent or repair the damage caused by reactive oxygen species
Oxidative stress - a situation in which the production of reactive oxygen species exceeds the ability of an organism to eliminate or neutralize them
Inverse association - a relationship between two variables in which they move in opposite directions

For references and more information, see the section on coronary heart 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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Flavonoids

What they do

General

  • Flavonoids are a type of phytochemical (a chemical produced by plants) that belong to a class of compounds called phenolics.
  • More than 5,000 varieties of flavonoids have been identified and hundreds of flavonoids can exist in a single food.
  • Many of the biological effects of flavonoids are related to their ability to modulate signaling pathways inside of cells.

Coronary Heart Disease (CHD)-specific

  • Inside endothelial cells (the cells that make up the lining of blood vessels), certain flavonoids may increase the production of nitric oxide, a gaseous molecule that promotes relaxation of arterial walls.
  • By improving endothelial cell function, flavonoids may help reduce the risk of progressing to more serious cardiovascular conditions, like atherosclerosis and CHD. 
What we know
  • Consuming flavonoid-rich food and beverages has been associated with a reduced risk of CHD.
  • Several randomized controlled trials have demonstrated that habitual consumption of certain flavonoid-rich beverages (black tea, purple grape juice, and high-flavanol cocoa powder) improves endothelial function in patients with CHD, elevated blood cholesterol, or type 2 diabetes.

For references and more information, see the section on cardiovascular disease in the Flavonoids article

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Phytosterols

What they do

General

  • Phytosterols are a group of plant-derived compounds that are similar in structure to cholesterol.
  • The two types of phytosterols are called plant sterols and plant stanols.
  • Foods rich in phytosterols include unrefined vegetable oils, whole grains, nuts, and legumes; enriched spreads are also a source of phytosterols.

Coronary Heart Disease (CHD)-specific

  • Phytosterols inhibit the absorption of dietary cholesterol.
What we know
  • Numerous randomized controlled trials have found that daily consumption of products enriched with plant sterols or plant stanols significantly lowers serum total- and LDL-cholesterol concentrations.
  • Approximately two grams of phytosterols per day reduces serum cholesterol by approximately 9 to 14 percent.
  • Due to their cholesterol-lowering effect, the addition of phytosterols to a heart-healthy diet (low in saturated fat and rich in fruit and vegetables, whole grains, and fiber) could further reduce the risk of CHD. 

For references and more information, see the section on cardiovascular disease in the Phytosterols article

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Resveratrol

What it does

General

  • Resveratrol is a phytochemical (a chemical produced by plants) that belongs to a class of compounds called stilbenes.
  • Some plants produce resveratrol to protect themselves from UV radiation, infection, injury, and other forms of environmental stress.
  • Resveratrol is naturally found in peanuts, grapes, red wine, and some berries.

Coronary Heart Disease (CHD)-specific

  • Test tube experiments demonstrate that high concentrations of pure resveratrol inhibit platelet aggregation, enhance the production of nitric oxide (a gaseous molecule that relaxes arterial walls), and inhibit inflammatory enzymes.
What we know
  • In humans, orally ingested resveratrol is modified by the digestive tract, greatly reducing the dose and modifying the form of resveratrol that reaches the circulation.
  • The presence of resveratrol in red wine was initially thought to be responsible for red wine’s beneficial cardiovascular effects. However, there is no evidence that resveratrol confers any reduction in CHD risk beyond that provided by the alcohol present in red wine.
DEFINITION
Platelet aggregation - the clumping together of platelets, a type of blood cell; an early step in the formation of a blood clot

For references and more information, see the section on cardiovascular disease in the Resveratrol 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 per day for men and one drink per day for women), alcoholic beverages have been associated with beneficial effects in the cardiovascular system.

Coronary Heart Disease (CHD)-specific

  • Moderate alcohol consumption appears to:
    • inhibit blood clot formation
    • increase HDL-cholesterol concentration
    • improve insulin sensitivity
    • exert anti-inflammatory effects
What we know
  • Moderate alcohol consumption is consistently associated with a reduced risk of CHD.

For references and more information, see the section on Potential Health Benefits of Moderate Alcohol Consumption in the Alcoholic Beverages article

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Coffee

What it does

General

  • Coffee is a complex mixture of chemicals. In addition to caffeine, coffee contains several bioactive compounds that can influence human health.

Coronary Heart Disease (CHD)-specific

  • Higher coffee intake has been associated with higher blood homocysteine concentration, a risk factor for the development of cardiovascular disease.
What we know
  • Randomized controlled trials have confirmed the homocysteine-raising effect of coffee at intakes of about four cups per day.
  • Although coffee consumption increases blood homocysteine concentration, there appears to be no significant association between moderate coffee consumption (three to four cups/day) and the risk of CHD.

For references and more information, see the section on cardiovascular disease in the Coffee article

Additional reference

  • Eilat-Adar S, et al., Nutritional Recommendations for Cardiovascular Disease Prevention. Nutrients. 2013;5:3546-3683

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Legumes

What they do

General

  • Foods in the legume family include beans, peas, lentils, soybeans, and peanuts.
  • Legumes are a good source of protein, essential minerals (magnesium, potassium, iron, zinc), vitamins (folate), soluble fiber, and phytochemicals.

Coronary Heart Disease (CHD)-specific

  • Legumes may benefit cardiovascular health by decreasing serum cholesterol concentration and by improving blood glucose and the insulin response.
What we know
  • Consumption of lentils at least four times per week is associated with a significantly reduced risk of CHD.

For references and more information, see the section on cardiovascular disease in the Legumes article

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Nuts

What they do

General

  • Nuts are a good source of soluble fiber, phytosterols, mono- and polyunsaturated fatty acids, protein, certain vitamins (folate, vitamin E), and minerals (calcium, magnesium, potassium).
  • Examples of tree nuts include: almonds, Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pistachios, and walnuts.
  • Peanuts are not nuts; they are legumes. However, peanuts are nutritionally similar to tree nuts and have some of the same beneficial health effects.

Coronary Heart Disease (CHD)-specific

  • The soluble fibers and phytosterols present in nuts and peanuts inhibit intestinal absorption of dietary cholesterol, which can lead to reductions in serum total- and LDL-cholesterol.
  • α-linolenic acid, an omega-3 fatty acid present in nuts and peanuts, may exert anti-arrhythmic effects.
  • Substituting dietary saturated fat with unsaturated fat lowers LDL-cholesterol and decreases cardiovascular disease risk.
What we know
  • Regular nut consumption (one ounce at least five times per week) is associated with a significantly lower risk of developing or dying from CHD.
  • Numerous randomized controlled trials demonstrate that adding nuts (one to two ounces daily) to a diet that is low in saturated fat results in significant reductions in serum total- and LDL-cholesterol concentrations in people with normal or elevated serum cholesterol.
  • A large randomized controlled trial conducted in Spain, the PREDIMED Trial, tested the effect of supplementation with olive oil or nuts on the prevention of cardiovascular events in high-risk individuals eating a Mediterranean diet.
    • Supplementation with olive oil (four tablespoons per day) or mixed nuts (approximately one ounce of walnuts, hazelnuts, and almonds per day) for about five years resulted in a significant, 30 percent reduction in the risk of major cardiovascular events (heart attack, stroke, and cardiovascular death).

HIGHLIGHT

  • Nuts are packed with healthy fat and, therefore, calories.
  • One ounce (28 grams) of nuts contains approximately 160 calories and 14 to 19 grams of fat (mainly mono- and polyunsaturated fatty acids).
  • One ounce of nuts equals approximately: 24 almonds, 8 medium Brazil nuts*, 18 medium cashews, 12 hazelnuts, 12 macadamia nuts, 15 pecan halves, 47 pistachios, 14 walnut halves, or 35 peanuts.
  • It is recommended to substitute nuts for sources of saturated fat.

*Depending on growth conditions, a single Brazil nut could contain exceedingly high levels of selenium.

DEFINITION
The traditional Mediterranean diet is characterized by:

  • high intake of olive oil, fruit, nuts, vegetables, and cereals
  • moderate intake of fish and poultry
  • low intake of dairy products, red meat, processed meats, and sweets
  • wine in moderation, consumed with meals

For references and more information, see the section on cardiovascular disease in the Nuts article.

Additional reference

  • Estuch R, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet. New England Journal of Medicice. 2013;368(14):1279-90

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Whole Grains

What they do

General

  • Whole grains are the seeds of plants belonging to the grass family, which includes wheat, rice, maize (corn), barley, oats, and rye.
  • Whole grain products contain all three layers of the seed: bran, endosperm, and germ.
  • In contrast to whole grains, refined grains are stripped of the bran and germ layers. Some essential nutrients (thiamin, riboflavin, niacin, iron) are added back to the grain after the refining process, producing what is known as an “enriched grain.”

Coronary Heart Disease (CHD)-specific

  • Whole grains contain several nutrients and dietary factors that are associated with CHD risk reduction:
    • whole grains are a source of folate, magnesium, and potassium
    • the soluble fiber present in certain whole grains (oats, barley) contributes to a reduction in total- and LDL-cholesterol
    • whole grains are a source of phytosterols, plant chemicals that interfere with the intestinal absorption of cholesterol
    • consumption of fiber-rich whole grains decreases dietary glycemic load, leading to slower absorption of glucose and a more sustained blood insulin concentration
What we know
  • Higher intake of whole grains (about three servings per day) is associated with significant reductions in the risk of CHD and ischemic stroke.

For references and more information, see the section on cardiovascular disease in the Whole Grains article.

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