You have undoubtedly heard a lot about the health benefits of antioxidants and the foods that contain them. Chocolate, coffee, tea, blueberries, grapes, red wine–I can enjoy those, you say. The antioxidants in carrots, spinach, kale and broccoli are not quite so popular.
It all started in the early 1990s when scientists began to understand the role of what are known as free radicals–atoms or groups of atoms formed as a result of the oxidation process that takes place naturally in the body through exercise, metabolism of foods and other bodily processes.
About one to two percent of cells become damaged through the oxidation process and become free radicals. They are called “free” because they lack a critical molecule and circulate through the body in search of a molecule to fill that need. When a free radical “steals” its needed molecule from another cell, that cell then becomes a free radical itself, trying to “steal” from another cell and triggering a chain reaction that can eventually lead to many disease processes, including cancer, Alzheimer’s disease and the atherosclerosis that is a major cause of both heart attack and stroke.
Toxins such as cigarette smoke, polluted air and pesticides in food and water generate additional free radicals, and the body simply isn’t able to generate enough antioxidants to counter this assault.
Antioxidants Offer Protection
Fortunately, protection can be obtained from foods containing antioxidants. These include readily available fruits and vegetables, many of which are highly colored and flavored such as those named at the beginning of this article. Other foods rich in antioxidants include tomatoes, nuts, seeds, whole grains and legumes.
The antioxidants in these foods are:
• vitamin C, which captures a free radical and neutralizes it before the chain reaction starts;
• vitamin E, which breaks up the chain reaction;
• beta carotene and other carotenoids;
• minerals such as selenium and manganese;
• flavonoids, which enhance the action of vitamin C and help protect blood vessels from rupture or leakage;
• phenols, polyphenols, phytoestrogens; glutathione, coenzyme Q10 and lipoic acid.
The body needs a good mix of these antioxidants. You can’t get your daily supply through chocolate and coffee alone. Nor can you load up on broccoli or kale, whether you like these foods or not.
That’s why good dietary advice stresses eating a variety of foods and at least five servings a day of fruits and vegetables. Follow that advice, and you’ll probably get the antioxidants you need.
The truth is that many Americans do not get their five servings a day, and those who are health-conscious are likely to turn to supplements to make sure they get an adequate level of protection. For those individuals, there is no shortage of antioxidant supplements available on the market.
Large epidemiological studies have shown that persons who eat greater quantities of fresh fruits and vegetables have a lower risk of heart attack, stroke, cancer and premature aging. But studies using supplements to test the health benefits of individual antioxidants generally have produced negative or inconclusive results.
Nearly 40,000 healthy women in the Women’s Health Study were assigned to take either 600 IU of natural source vitamin E or placebo every other day. After 10 years, the rate of heart attack, stroke and cancer were about the same in the two groups. Subjects taking vitamin E, however, were 24 percent less likely to die of a cardiovascular cause.
In the HOPE (Health Outcomes Evaluation) trial, subjects all had previously diagnosed heart disease or a high risk of it. The rate of heart attacks and stroke was essentially the same in the two groups, but the vitamin E group had a higher risk of heart failure and hospitalization for heart failure. An Italian study of heart attack survivors also found no beneficial effects of vitamin E over a three-year period.
A few studies have gone the other way, but for specific populations. The Women’s Antioxidant Cardiovascular Study, for example, found a significant benefit for vitamin E among women with existing cardiovascular disease. And a study from Israel found a marked reduction in heart disease among type 2 diabetics taking vitamin E.
Beta carotene conveyed no significant reduction in heart attack risk, according to the Physician’s Health Study, but smokers in the study had an increased risk of lung cancer. This raised the issue of side effects and interactions of antioxidants with other substances.
A combination of antioxidants–120 milligrams of vitamin C, 30 milligrams of vitamin E, 6 milligrams of beta-carotene, 100 micrograms of selenium and 20 milligrams of zinc–were compared to placebo in a French study. They showed no effect on rates of cardiovascular disease.
As to overall intake of antioxidant substances, a Dutch study of 5,400 subjects age 55 and over measured antioxidant intake over a 14-year period. The majority of these antioxidants were from coffee and tea, and subjects with the highest total intake were no less likely to have a stroke than those taking a placebo. The researchers concluded that eating certain antioxidant-rich fruits, vegetables and other foods was probably more beneficial than consuming a high total number of antioxidants.
While failing to reveal a magic solution to protect against the damage caused by free radicals, none of these studies can be taken as conclusive. The period of followup may have been too short, the dose could have been either too small or too large.
Most believe that antioxidants cannot be taken away from the natural context of the foods in which they exist and still provide the same benefits. There are other nutrients in blueberries, grapes, tomatoes, chocolate, tea and red wine that may offer benefits independent of the antioxidants they contain or in combination with them.
While antioxidants may have become overly hyped, there is no risk and substantial benefits to be gained from eating a good diet, rich in fruits, vegetables, nuts and whole grains.
REFERENCES:
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“Antioxidants: beyond the hype,” Nutrition Source, Harvard School of Public Health.
Alberto Ascherio, “Antioxidants and Stroke,” American Journal of Clinical Nutrition, 200;72:337-338.
Darron Baker, “How antioxidants could help to reduce heart attacks and strokes,” Atherogenics.com..
Gemma Chiva Blanch, et al, “Effects of wine, alcohol and polyphenols on cardiovasculr disease risk,” Alcohol and Alcoholism, 2013;48(3):270-277,
Britt Burton-Freeman, “Tomato consumption and health,” American Journal of Lifestyle Medicine, 2011;5(2):182-191.
“Can antioxidants in fruits and vegetables protect you and your heart?” Heart.org, posted by Saundra Young, CNN Medical Senior Producer, updated July 22, 2013.
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Frank Enseleit, et al, “Effects of pycnogenol on endothelial function in patients with stable coronary artery disease,” European Heart Journal, 2012;33(13):1589-1597.
Samuel Grief, M.D., “Mediterranean diet–why should we adopt this diet?”Nutritalk blog, March 13, 2009.
Samuel Grief, M.D., “Eggs: are they really good or bad for you?” NutriTalk blog, July 29, 2009.
Sanjay Gupta, “Antioxidants in coffee, tea may not help prevent dementia, stroke,” CNN Chart blogs, February 13, 2013.
\Sue Hughes, “More light shed on mechanism behind harmful effect of smoking,” Heartwire, May 16, 2000.
P. Kar, et al, “Flavonoid-rich grapeseed extracts: a new approach in high cardiovascular risk patients?” International Journal of Clinical Practice, 2006;60(11)L1484-1492.
G.F. Key, “Cardiovascular disease and vitamins. Concurrent correction of ‘suboptimal’ plasma antioxidant levels may be an important part of ‘optimal’ nutrition, help to prevent early stages of cardiovascular disease and cancer, respectively,” Bibl. Nutr Dieta, 1995;52:75-91.
“Smokers blow away antioxidants that protect against heart disease,” Medscape Medical News, May 16, 2000.
Malcolm Taylor, M.D., Antioxidants good for your heart?” OneMedical.com, November 2, 2012.
11/20/2013
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