“Resveratrol extends lifespan”

Resveratrol genuinely does extend lifespan in simple organisms - baker's yeast, roundworms and fruit flies all live longer on it [1]. The question is whether that carries over to mammals.

A 2006 experiment was the reason people thought it might. Middle-aged mice fed a high-calorie, high-fat diet survived longer on resveratrol, and also showed better insulin sensitivity, more mitochondria (the structures inside cells that generate energy) and improved motor function [1].

Those mice were obese and metabolically unwell to begin with. The obvious next question was whether resveratrol also helps animals that are already healthy.

The same research group answered it two years later. Mice on a standard diet, started on resveratrol at 12 months of age (roughly middle age for a mouse), did show real improvements: less protein leaking into the urine, less inflammation, more elastic arteries, better motor coordination, fewer cataracts and better preserved bone density.

But those mice did not live any longer than the untreated ones [2]. The researchers said so in the title of the paper.

That split is the whole story. Resveratrol looks like it offsets some of the harm of a poor diet rather than slowing ageing itself.

In people, the longest study reviewed here followed 783 adults aged 65 and over in two Italian villages for nine years. Rather than rely on food questionnaires, the researchers measured resveratrol directly, testing urine for the breakdown products the body makes from it.

268 of those people died over the nine years. Those with the most resveratrol in their bodies were no more likely to survive than those with the least, and resveratrol levels showed no link to inflammation markers, heart disease or cancer either [3].

Two limits are worth stating plainly. That study watched people rather than assigning them resveratrol, and it captured the amounts you get from an ordinary diet, not the much larger doses sold in capsules.

Neither limit rescues the claim. No human trial in this evidence base has tracked how long people lived, so the honest position is that resveratrol has not been shown to extend human lifespan - not that it works at higher doses and simply has not been measured yet.