It's possible that in this case, the mice didn't begin resveratrol treatment when they were young enough to get the full benefits of the compound, perhaps including a longer life, Sinclair says. Also, unlike humans, mice don't die from cardiovascular disease or suffer serious consequences from brittle bones, so it's possible that resveratrol may be an even greater boon to aging humans than it is to mice, says Rafael de Cabo of the National Institute on Aging, who also worked on the project.

Sinclair's team also monitored gene activity patterns in various tissues in the treated mice and found that they were similar to those in animals on a restricted-calorie diet. Scientists have found that reducing mice's caloric intake by 30 to 50 percent while maintaining adequate nutrition can ward off age-related diseases, improve stress resistance, and slow the declines in function that come with age in many species, including mice, fish, and yeast. Mice treated with resveratrol in this study "have a younger gene-expression profile," de Cabo says.

It's not exactly clear how resveratrol works. There's evidence that the compound activates proteins called sirtuins that play a key role in controlling aging. However, a recent study using lower doses of resveratrol in mice suggests that there may be another mechanism at work, at least when lower doses are given.

The daily dose of resveratrol that Sinclair and his colleagues gave mice was the equivalent of more red wine than most people will drink in a lifetime, so "wine isn't going to do the trick," says Leonard ­Guarente, a professor at MIT and a pioneer in the study of sirtuins. (Guarente is on the board of Sirtris but didn't work on this study.) "There's going to have to be a supplement," he says.

Resveratrol pills are already on the market, but until more studies are done in humans, de Cabo advises caution. Even though you'll get much less of the compound by eating berries and drinking wine, he says, "I'd rather people buy grapes and red wine than take compounds off the shelf."

Sirtris is conducting clinical trials using resveratrol to treat type 2 diabetes. The preliminary results look promising, and no serious side effects have surfaced, notes Sinclair.

He and other scientists are also studying the anti-aging properties of similar compounds--some of them apparently much stronger than resveratrol. "There's a whole pipeline of better molecules coming along," Sinclair says.