It is known that calorie restriction increases stem cell capacity in aging, thereby helping to maintain tissues for longer. From Extreme Longevity, a recent commentary on the mechanisms involved: "Like it or not food lovers, the single most effective known means of extending animal lifespan is through reducing daily caloric intake. Though not definitively proven in humans, the success of this intervention has been demonstrated in myriad species in more than 50 years of research. ... A protein called mTOR is responsible for this effect. mTOR combines with two other proteins to mediate several important cellular processes. These include translation of mRNA into protein, mitochondrial activity, and autophagy. Caloric restriction inhibits mTOR activity which leads to longer lifespan. The new studies [convincingly] demonstrate that reduction of mTOR activity causes preservation of stem cell health. They increase in abundance and proliferative potential. One study shows this occurs in intestinal cells, and the other in muscle cells. In the instestinal cell study, the authors showed that it was actually supporter cells called Paneth cells that aided the health of stem cells when they were taken from calorie restricted animals. They further showed this effect was mediated by mTOR inhibition and that it was achieved by increasing the activity of another protein called Bst1, important in cell proliferation. In the muscle study, calorie restricted animals had greater muscle stem cell proliferative capacity too. And this effect was also seen when the stem cells were transplanted into non calorically restricted animals, suggesting the microenvironment or niche around the stem cells was key. ... taken together, the two studies indicate that preserving and enhancing stem-cell function in multiple tissues is one of the ways in which calorie restriction slows the ravages of aging."