Pretty soon we'll all be chowing down on grape skin extracts. I actually tried this stuff several years ago and thought it increased my joint stiffness...so I stopped. Many scientists recommed caution before plunging into yet another food supplement fad.
Anyway, here is the latest bit from a Nature article:
"Resveratrol (3,5,4'-trihydroxystilbene) extends the lifespan of diverse species including Saccharomyces cerevisiae, Caenorhabditis elegans and Drosophila melanogaster. In these organisms, lifespan extension is dependent on Sir2, a conserved deacetylase proposed to underlie the beneficial effects of caloric restriction. Here we show that resveratrol shifts the physiology of middle-aged mice on a high-calorie diet towards that of mice on a standard diet and significantly increases their survival. Resveratrol produces [biochemical] changes associated with longer lifespan......"