Scientists are learning more about how plant compounds work together with traditional anti-oxidant vitamins to provide protection that is superior to that of vitamins alone.

A diet that is rich in fruits and vegetables contains not only anti-oxidant vitamins but also various polyphenols. Many of the benefits derived from eating such diets may be the result of synergism between plant polyphenols and the better-known vitamin anti-oxidants. Plant polyphenols are the active anti-oxidant compounds found in tea, wine and grape juice.

Overwhelming evidence supports the belief that excessive oxidation and free radical damage is linked to various disease states and even to aging. Yet studies in both animals and humans, in which diets were supplemented with anti-oxidant vitamins for long periods of time, have yielded ambiguous results.

At the 219th American Chemical Society National Meeting held in San Francisco on March 26 - 30, 2000, researchers presented new studies that support supplementing the diet with special plant-derived nutrients and for consuming more whole fruits and vegetables.

In his paper, Professor Joe Vinson of the University of Scranton pointed out that anti-oxidant vitamins are present in the human body at levels typically twenty to several hundred times those of plant polyphenols. This is one reason why so much research has focused on the anti-oxidant vitamins in foods and relatively little research has been done on the anti-oxidant roles of the other compounds present. Now, however, it is becoming clear that these non-vitamin plant anti-oxidants may impact the anti-oxidant status of the body beyond their representation in the blood and tissues. An extract from grape seeds given to human volunteers led to a much greater increase in the anti-oxidant capacity of the subjects' blood than was theoretically possible. The same grape seed extract demonstrated significant synergism when tested with the anti-oxidant vitamins C and E, either alone or in combination.

In another paper, Dr. Chithan Kandaswami of the State University of New York at Buffalo reported that grape seed extract also acts in ways other than as an anti-oxidant. The flavonoids found in grape seed along with chemically similar compounds found in other plants act to reduce the signals received by certain cell receptors involved in inflammation and tumor growth. Anti-oxidants commonly are found to help to reduce inflammation, but in this case the protective effect is different from an anti-oxidant benefit.

The results of these and other recent studies on the polyphenolic compounds found in grapes, wine, tea and other foods underscore the importance of eating diets rich in whole fruits and vegetables.

Dr. Clouatre is the author of several books on nutritional supplements.

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