QUESTION: I have heard a lot about anti-oxidants and health. Since I have no idea what an anti-oxidant is, I thought I would ask you to discuss this topic in your column. Thank you.

ANSWER: I have received several requests for information about anti-oxidants but have hesitated to discuss this topic because there is so much unreliable information about them. However, the April issue of the Tufts University "Diet and Nutrition Letter" discussed this topic, and since this is a reliable source, I will summarize some of the material from that discussion for you.First, the reason we need anti-oxidants is that some of the chemical reactions that use oxygen, both in the body and in the environment, create compounds that are very toxic. These toxic compounds, which can injure body cells, are commonly referred to as free radicals.

Of course the body has a free radical defense system of its own to combat these compounds composed of some of the anti-oxidants we eat, such as beta-carotene, vitamin C and vitamin E, as well as a set of enzymes manufactured by the body. Interestingly, each of the defense enzymes contains a metal, such as copper or iron, and one contains selenium. That's why some people think of selenium as an anti-oxident. It's not really; it is an essential part of an anti-oxidant enzyme.

All of the anti-oxidants work to deactivate the free radicals, but they do their jobs in different parts of a cell or with different kinds of reactions. For example, vitamin C works in the watery inner part of the cell because it is water soluble, whereas vitamin E, a fat-soluble vitamin, stays within the fat-containing cell membranes. Beta-carotene appears to act effectively in places that have a low amount of oxygen.

Does taking extra anti-oxidants slow the aging process? This is a tough question to answer. It is clear that millions of free radicals are formed each day. If a few of these were not squelched, a little bit of damage could accumulate over time and cause premature aging. Some experts speculate that if you had higher levels of anti-oxidants to protect against free radicals, you could perhaps slow the damage. However, experiments with animals given anti-oxidants have not confirmed the benefit of this treatment in terms of aging.

What about anti-oxidants and disease? This question is a little easier to answer, since a number of studies have shown that people who have a higher intake of anti-oxidants also have a lower incidence of cancer. This makes sense since the formation of cancer is probably related to damage to a component of cells called DNA, which can be caused by free radicals. There is evidence that a low anti-oxidant level is associated with an increased risk of cancer. There is also some preliminary evidence that beta-carotene can reverse clogging of the blood vessels in heart disease. Even rheumatoid arthritis may be helped in some cases by anti-oxidants.

So, how do we get a greater intake of anti-oxidants? The best way is to increase the intake of fruits and vegetables, especially citrus fruits, dark yellow and orange fruits and vegetables as well as dark leafy greens - apricots, pumpkin, carrots, squash, spinach, broccoli and cantaloupe. The evidence concerning taking an anti-oxidant supplement or not is not so clear. For now, the best treatment is to improve the quality of your diet.