Although antioxidants help to defend our bodies’ cells against oxidative stress, research has shown that dietary supplements containing these substances may not always be beneficial.
Extensive studies have evaluated the effects of antioxidant dietary supplements—particularly vitamin E and beta-carotene—on chronic diseases associated with aging. The antioxidants were not found to be helpful for preventing cancer, cardiovascular disease, or cataracts. However, certain supplements containing a combination of antioxidants and zinc were shown to slow the progression of age-related macular degeneration (an eye disease).
Antioxidant supplements may have harmful effects if taken at high doses. In particular, high-dose beta-carotene supplementation can increase the risks of lung cancer and cardiovascular disease. These effects have been seen primarily in people at high risk of these diseases, such as smokers.
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