New research suggests that gut bacteria are responsible for increased longevity in calorie restricted diets.
Choline is made available for absorption from the intestine by the activities of the gut bacteria that are liberating it for their own purposes. The amount of aliphatic amines in urine is thus an indirect measure of how much choline is available. As in the case of creatine, this differed between the two groups. Dogs on the restricted diet had lower levels of the amines in their urine than did their well-fed counterparts—implying that less choline was being made available. And if less choline were available, that would limit a dog's ability to metabolise fats, and thus restrict its metabolic rate.Since Americans aren't likely to cut back on calories anytime soon, how much you want to bet that there are scientists trying a way to modify the gut bacteria to get the same longevity increase without requiring the caloric cutback?
The apparent drop in choline levels was much greater than could be accounted for by a relative lack of food, so Dr Nicholson suspects that the restricted diet was also causing the composition of the dogs' gut flora to change in a way that did not favour choline-munching bugs.
via The Economist