Confused about antioxidants? Roger S. Blumenthal, M.D., Professor of Medicine, offers bottom-line advice.
By now most people have heard the claims that antioxidants can ward off chronic diseases, preserve good vision, cure arthritis, and perform other miracles. The main antioxidants in foods are vitamins C and E; carotenoids such as beta-carotene, lutein, and similar plant compounds; and the mineral selenium. There are many other antioxidant compounds, including ones the body itself manufactures—chiefly enzymes, which can destroy harmful products of metabolism.
Not surprisingly, antioxidant supplements, especially vitamins C and E and beta-carotene, have been enjoying a big boom in popularity. But do the antioxidant supplements deserve such popularity? Not only have three review articles questioned the benefits of these antioxidant supplements, but a study from Johns Hopkins has even suggested that vitamin E supplements may actually be harmful. If you take any of these antioxidant supplements, should you stop?
What are antioxidants and how do they work?
An antioxidant "quenches" free radicals. Free radicals are unstable molecules -- missing one or more electrons -- that are created continuously in the body during the normal process of "burning" food for energy so that cells can function. Other factors -- pollution, smoking, sunshine, even exercise -- also create free radicals. Because electrons prefer to exist in pairs, free radicals will "steal" electrons from other molecules in cells, leaving new unpaired electrons in their wake. Healthy cells usually are able to repair this damage, but, over time, the process can wear them down and harm proteins, cell membranes, and genetic material. It's thought that free radical damage is at the root of aging and such chronic diseases as coronary heart disease and cancer.
In this ongoing battle, antioxidants are the peacemakers. The idea behind antioxidant supplements is that if some antioxidants are good, then more and more of them would be better -- a notion that unfortunately rarely holds true when you're speaking of food or, especially, of nutritional supplements.
Roger S. Blumenthal, M.D., Professor of Medicine and Director of the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease, explains that the research on antioxidant supplements suggests that if you’re taking them to prevent heart disease, you’re probably wasting your money. In 2004 three review articles found no benefit from antioxidant supplements. The American Heart Association Science Advisory, published in Circulation, based its conclusions on data collected from clinical trials on vitamins C and E, beta-carotene, and antioxidant “cocktails” (a single supplement containing a combination of antioxidants).
Another review, published in the Archives of Internal Medicine, found that vitamin E supplements did not prevent cardiovascular events such as heart attacks and strokes.
A third article, in The Lancet, addressed cancer risk. Data on more than 170,000 people revealed that beta carotene and vitamin A, C, and E supplements -- taken alone or in combination -- did not reduce the risk of many cancers, including esophageal, colon, pancreatic, and liver cancer.
Furthermore, there's the lurking possibility of harm. Researchers from Johns Hopkins analyzed data from 14 studies and found that vitamin E supplements in dosages of 400 IU or greater raise the risk of death. It is important to note that it is impossible to consume this much vitamin E from food alone. The typical American diet supplies just 6 to 10 IU daily; the recommended daily allowance for vitamin E is about 22 IU daily.
Much of the fanfare for antioxidant supplements came from the largely unregulated industry that manufactures and sells them. But many doctors recommended antioxidant supplements because of the recognized dangers of free radicals and because some benefits were reported from observational studies of people taking antioxidant supplements and eating antioxidant-rich foods. The trouble with such observational studies is that 1) they could not tell whether antioxidant supplements caused the benefits; 2) people may not accurately report what they eat; and 3) the health-conscious people who usually take part in such research may be less likely to smoke and more likely to practice other good health habits. These factors -- or a combination of them -- may be responsible for the protective effect attributed to antioxidant supplements. So these benefits may only be a perception -- not real.
Meanwhile, test-tube studies have found that high doses of antioxidants can turn into pro-oxidants, in other words, produce free radicals. Antioxidant supplements, unlike the nutrients found in food, may somehow upset the balance of antioxidants absorbed into the body. Carefully controlled clinical trials, the gold standard in medical research, have not yet found any positive evidence for antioxidant supplements.
Bottom line advice: In special cases, your doctor might prescribe a supplement to treat a specific condition. People with certain eye conditions may be prescribed a supplement containing beta-carotene, for example. And a multivitamin supplement is still a good idea to fill nutritional gaps in your diet. In most instances, though, our advice is not to spend your money on vitamin E or C, selenium, or beta carotene supplements, or on any of the antioxidant cocktails on the market. To help your body fight aging and disease caused by free radicals, your best course of action is to eat a diet rich in fruits, vegetables (especially leafy greens), and whole grains. Nuts, in moderate amounts, are an excellent addition. Use plant-derived oils such as canola, olive, and peanut oil for cooking and salads. Include some lean meats and low-fat or nonfat dairy products. A healthy diet should be your chief source of vitamins, minerals, and other life-giving nutrients.
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