A growing number of scientists suspect that the breakdown of mitochondria is among the most important causes of cell-level changes that eventually cause the body's tissues to degenerate with age. The damage accumulates gradually until hitting some critical mass of malfunction, at which point diseases arrive rapidly. That may be why so many diseases first occur during middle age, and become steadily more common afterwards.

Repair and prevent this damage, say proponents of the mitochondrial theory of disease, and those afflictions can be averted.

Resveratrol, which also occurs naturally in red wine, didn't extend the maximum lifespan of the mice in an experiment, but it did protect them from the ravages of aging.

http://blog.wired.com/wiredscience/2008/11/two-mice-on-tre.html