A. Although it was first identified in 1974, almost all the research on resveratrol has been done since 1992, when it was found in red wine and credited to be partly responsible for the "French paradox." The "French paradox" is a name for the observation that people in France have a relatively low incidence of coronary heart disease, despite a diet rich in saturated fats.
Resveratrol is found in grapes, mulberries, peanuts, and other plants, apparently produced by these plants for its antifungal properties. The amount of resveratrol in different foods varies greatly, depending on growing conditions (such as humidity), which affect the risk of fungal disease to the plant. The amount of resveratrol in wine also varies from as little as 0.05 milligrams per liter in some white wines to 40 milligrams per liter in wines from certain muscadine grapes, so the pills are a more reliable source without the complication of the alcohol content.
The mechanism for resveratrol's benefits are not fully understood, but among other things it seems to reduce the absorption of fat and thus mimic calorie restriction. In animal research it has increased the lifespans of worms, fruit flies, and mice, but it is not known whether resveratrol will have similar effects in humans. It is not suspected to be toxic, but there have been few controlled clinical trials. In rats, daily oral administration of resveratrol at doses equivalent in humans to over 15,000 milligrams per day for four weeks resulted in no apparent ill effects.
Resveratrol has been registered as an "investigational new drug" and is excluded from the definition of a "dietary supplement" under the Dietary Supplement Health and Education Act because it was not marketed before 1994. However, resveratrol as a concentrate from food sources is available in pills containing anywhere from 10-50 milligrams. Quercetin and other natural antioxidants are often included in resveratrol pills because these appear to prolong the activity of the resveratrol. A major criticism of resveratrol is that it is destroyed extremely rapidly by the liver, so rapidly that most of it disappears from the bloodstream in less than 30 minutes after it is consumed. Theoretically at least, taking four or more small doses of resveratrol per day would be better than taking one large dose.
In humans resveratrol may protect against cancer and heart disease. Recent evidence suggests that resveratrol acts not only as an antioxidant but also as a signaling molecule within cells to change the expression of genes. Such capability would go a long way toward explaining the large variety of beneficial effects on body systems that resveratrol has shown. For instance, resveratrol seems to block all three steps of cancer growth (initiation, promotion, and progression), as well as inhibit both the synthesis and release of inflammatory molecules and influence the production of nitric oxide (which affects blood clotting). Resveratrol may also have the ability to send a signal to cancer cells to "commit suicide" (the medical term for this is "apoptosis"). For scientists the challenge is to understand and harness the power that substances such as resveratrol possess.
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