Resveratrol is an antioxidant dietary supplement that is widely promoted to help prevent several age-related and malignant diseases. It's sort of the supplement du jour.

The term seems to be a combination of res-, from resinous and veratr- from Veratrum grandiflorum, the plant species in which it was found. Native to Asia, it is in the buttercup/hellebore family, a source of many plant parts that have been used medicinally. Interestingly, the genus Veratrum is listed in Webster's Dictionary as a poisonous herb.

The Sept. 21 Medical Letter had a short summary of resveratrol. Sent to subscribing doctors, this publication's specialty is summarizing the current essence of a subject as objectively as possible.

Resveratrol was first isolated in Japan from the roots of white hellebore in 1940, and later in 1963 from Japanese knotweed roots, the main source for today's capsules. It gained wider attention in 1992, when its presence was suggested as an explanation for the cardio protective effects of red wine, called the "French paradox" (not two French doctors).

Because of extensive media coverage (exploitation?), sales of resveratrol as a supplement have soared since 2006.

But what is it supposed to do - and what can we prove it actually does?

The label on the Walgreen's Finest Naturals says: "Resveratrol provides superior antioxidant protection and helps to promote cardiovascular health. (Small print: The Food and Drug Administration has not evaluated these statements. This product is not intended to diagnose, treat, cure or prevent any disease.)" Why are they selling it?

The indirect, implied claims include protecting hearts, preventing cancers, lowering blood sugars, slowing down aging (a proposal made for anything that is an "antioxidant," such as vitamin E, etc.), and being anti-inflammatory. The problem is that there are no data from humans trials, save one study where resveratrol, taken in high doses (3 to 5 grams) lowered blood sugar.

Experiments in other critters have shown that resveratrol treatment extended the lives of a type of yeast, Saccharomyces, fruit flies, nematode worms (parasite) and short-lived fish (the little-bitty sunfish that I catch?).

It did not increase the life span of mice, with the exception of obese ones, but it may retard the aging process in mice. There have been dozens of studies of resveratrol's anti-cancer activity in animal models. It did suppress the growth of tumors of skin, breast, gastrointestinal tract, prostate and lung.

The difficulty in translating these effects to humans is the problem of absorption. Once consumed, it is rapidly metabolized by the intestines and liver, the first organs to process it. Its metabolized forms have not been studied for biological effect at all. The theory that resveratrol from wine could have higher absorption than from a pill has been disproven by two studies (darn).

All the biochemical studies seem to find the same genetic pathway activated, Sirutin 1, which improves the function of all cells' power plants, called mitochondria. Curiously, calorie-restriction studies of mice showed much similar results in heart function and other markers of aging.

Adverse effects of resveratrol consumption are not yet known. To date, nothing reported is detrimental, even in the few human studies with "large doses."

The idea of a so-called "natural substance" being able to inhibit our aliments is always beguiling. One reader told me she has taken it for a few months, and has seen results on her trips to the scale that are far better than average. It is so problematic to sort through the haystacks of claims and hyperbolic hype to find the needle of truth - and not get stuck by it.

It seems as though someone is always selling hope in bottle, whether it is liquid, lotion, cream, pill or potion. Just remember not to replace good old grub with too many supplements.

Frank Bures is a dermatologist in Winona.