Antioxidants are substances that help to counteract the cell damage that results when compounds called free radicals are formed during normal metabolism. Free radicals can help the body fight bacteria and viruses, but they can also damage cell membranes and DNA. Excess free radical production may contribute to many diseases, including heart disease and cancer.
A variety of antioxidants either neutralize free radicals or repair the damage caused by them. Foods that contain antioxidants—vitamins C and E, the mineral selenium and plant pigments known as carotenoids (which include beta-carotene)—can add to the body’s supply of antioxidants.
Each antioxidant has a different mode of action, and many of them appear to work together.
Therefore, it’s important that your diet supply adequate amounts of all of the antioxidants to achieve this synergy.
But supplements may not be the answer. In fact, an analysis of 47 randomized, controlled trials of 181,000 people found that taking high doses of vitamin A, vitamin E or beta-carotene can raise the risk of death by 16 percent, 4 percent, and 7 percent, respectively. Taking vitamin C did not increase the risk of death, but offered no apparent benefit, either.
When it comes to antioxidants, here’s what we recommend.
1. Get most of your antioxidants from a variety of fruits and vegetables, not from supplements. It’s possible that antioxidants are only beneficial when consumed in combination with each other or with other substances in plant foods. Studies have shown that consuming at least 2.5 cups of vegetables and fruits per day is associated with a reduced risk of cardiovascular disease, including heart attack and stroke. If you eat 2 cups of fruit and 2.5 cups of vegetables (nine servings of fruits and vegetables) a day, as the Dietary Guidelines recommend for a 2,000-calorie-a-day diet, you will easily get enough antioxidants. Focus on eating whole fruits rather than drinking 100 percent fruit juice, because juice doesn’t contain fiber, and you may consume excess calories if you drink too much. Nuts and sunflower seeds are also rich in vitamin E. (Unlike fruits and vegetables, however, they are high in calories and should be eaten in moderation.)
2. Focus on dark green vegetables and orange, red and yellow fruits and vegetables. Fruits and vegetables of these colors are the most nutritious. They provide substantial amounts of antioxidants as well as other beneficial nutrients.
3. Don’t take any antioxidant supplements without first talking to your doctor. This is particularly important if you’re thinking of taking selenium, beta-carotene, or vitamin A or E supplements. These supplements can be dangerous to your health when taken at high doses. For example, the difference between an adequate and toxic dose of selenium is quite small. People concerned that they are not getting enough selenium should consider a multivitamin-mineral supplement that contains no more than the RDA for selenium (55 mcg).
Beta-carotene supplements increase lung cancer risk in smokers. In excess, vitamin A supplements can increase the risk of death. Vitamin E reduces the ability of the blood to clot. Consequently, it is crucial to check with your doctor before supplementing with vitamin E if you take anticlotting medications such as warfarin (Coumadin) or aspirin.