In light of recent research into the effects of calorie restriction on those little plants and animals that live in your gut, this would seem interesting: "The intestinal microbiota is important for maintenance of host health, providing energy, nutrients and protection against invading organisms. Although the colonic microbiota is relatively stable throughout adult life, age-related changes in the gastrointestinal (GI) tract, as well as changes in diet and host immune system reactivity, inevitably affect population composition. Recent studies indicate shifts in the composition of the intestinal microbiota, which may lead to detrimental effects for the elderly host ... These changes, along with a general reduction in species diversity in most bacterial groups, and changes to diet and digestive physiology such as intestinal transit time, may result in increased putrefaction in the colon and a greater susceptibility to disease. Therapeutic strategies to counteract these changes have been suggested in ageing people." Will this turn out to have as much of an effect on healthy longevity as, say, exercise or calorie restriction? Possibly, you never know. Invariably, these line items pale before the future of longevity science, however - stay focused on the big picture.