Antioxidant supplementation for health - a boon or a bane?

Abstract

Antioxidants (vitamins E and C, β-carotene, superoxide dismutase [SOD], catalase etc.) are the substances that protect cells from the damage caused by free radicals, formed as a result of oxidative stress. Free radicals (O 2− , H 2 O2, OH− , ROO− etc.) are generated during the cellular metabolism and also due to environmental effects (cigarette smoke, ionizing radiations). Excessive production of free radicals has been implicated in the causation and progression of several diseases, e.g., atherosclerosis, cancer, rheumatoid arthritis, diabetes, and cataract. The general belief is that since free radicals are bad for health, antioxidants are good. This led to an indiscriminate use and supplementation of antioxidants, which is currently a controversial issue. This review gives an updated information on the effects of supplementation of antioxidants (vitamins E and C, β-carotene, SOD, catalase etc.). While some studies suggest that antioxidants are beneficial and protective, other interventional trials showed no health benefits. There are some interventional studies which demonstrated the deleterious effects of antioxidants (high risk of cancer, increased mortality). Further, antioxidant supplements were found to diminish the beneficial effects of certain drugs. It is suggested that indiscriminate use of antioxidant supplements should be avoided. Perhaps, antioxidants may be prescribed (not exceeding the recommended daily allowance) to the elderly, strict vegetarians or people who are on calorie-restricted diets. It is advisable that the antioxidants are consumed from rich natural dietary sources rather than supplements. Further, healthy individuals should exercise utmost caution while overdosing themselves with antioxidant supplements.