Resveratrol
An antioxidant polyphenol found in grapes, red wine and some berries, popularised as an "anti-ageing" molecule that activates sirtuins, though the evidence is debated.
Resveratrol is a polyphenol from the stilbene family, produced by certain plants (grapes, blueberries, peanuts) in response to stress (fungal attack, UV). It is best known as the “health” compound in red wine.
The original angle (sirtuins and the wine myth): resveratrol hit the headlines after studies suggested it activates sirtuins (SIRT1), longevity enzymes that are also activated by calorie restriction. Hence the appealing idea of a “molecule that mimics the benefits of fasting”. Effects on longevity have been observed in yeast, worms and mice.
The big spoilsport: in humans, the evidence is very disappointing. Worse, the amount of resveratrol in wine is tiny: you would need to drink tens to hundreds of litres of wine a day to reach the doses used in animal studies. The idea that “red wine is good for the heart thanks to resveratrol” is therefore largely a myth: the harms of alcohol far outweigh any hypothetical benefit. No health authority recommends drinking wine for your health.
The “French paradox” (low heart disease mortality despite a rich diet) is probably due to the Mediterranean lifestyle as a whole (vegetables, olive oil, sociable meals and so on), not to the resveratrol in wine.
Xenohormesis: resveratrol is a good illustration of the xenohormesis theory. It is a defence molecule of the stressed plant which, in us, activates resilience pathways (sirtuins, Nrf2). Its potential value would come from this hormetic signal rather than from a direct antioxidant effect.
Supplements: resveratrol as a supplement (at concentrated doses) is being studied, with mixed results (poor bioavailability, inconsistent effects). It is not the anti-ageing pill that was hoped for.
Sources: grapes (especially the skin), blueberries, cranberries, peanuts, cocoa. Eating whole grapes makes more sense than counting on wine.