To bring resveratrol cheaply to a growing market, supplement makers have taken to extracting the plant compound not from grapes or wine but from an exotic weed -- Polygonum cuspidatum, or Japanese knotweed. They are mixing it with a wide variety of other dietary supplements (including the antioxidant acai, which also has taken the supplements world by storm), concentrating it in mega-doses, micronizing it "for optimum absorption" and capturing it in a pill, capsule, powder and even a topical cream.

Among its many commercial manifestations, resveratrol is sold as Trans-Max, Nitro-250, Vindure, Sustain-Alpha, Resveratrol-Forte and Resveratin. Supplements may contain as little as 25 milligrams and as much as 1 gram of resveratrol per dose.

A question of dose

The flurry of commercial activity has taken off despite the fact that researchers don't even know exactly what resveratrol does.

Betz and others vying for a share of that market say there is no need to wait until a welter of slow-moving clinical trials has established resveratrol's life-extending powers in humans, not to mention its safety, to encourage the use of large doses.

"I feel there is virtually no evidence so far -- and resveratrol has been around for quite awhile -- of harm," he says. "And I feel given the data we have now, which concludes it has benefits in terms of so many diseases . . . that it will do more harm than good not making it available."

But until clinical trials provide the answers to questions on, among other things, the proper dose, Rafael de Cabo, a National Institute on Aging investigator who has co-authored most of the pioneering studies on resveratrol, says he wouldn't consider taking a resveratrol supplement. And he certainly would not recommend them.

At the same time, DeCabo acknowledges that many scientists and physicians, impressed by research suggesting resveratrol's potential to forestall diseases of aging, have set aside such scientific discretion and publicly acknowledged they take resveratrol supplements.

"I know many intelligent people who are taking it," DeCabo says. "They are taking their health in their own hands."

DeCabo and colleagues have found that at very high doses -- far higher than any supplements currently on the market -- resveratrol was toxic to mice after six months. While the compound has appeared generally free of side effects in animals, DeCabo warns that "everything has a toxicity" and that resveratrol's limits of safety are far from clear.

"We need to understand exactly how these molecules work, at what doses and for what disease" before offering them on the open market, he says. "Unless you have scientific evidence, you're a snake oil seller."

melissa.healy@latimes.com