The fact that a calorie restricted (CR) diet can extend the median and maximum lifespan of multiple organisms has been known for decades, but the mechanism remains undefined. A December 2006 PNAS paper links a long-term CR diet to a delay in immune senescence in nonhuman primates, suggesting that cutting calories may prolong life by preserving the efficacy of the immune system. In the study, young adult monkeys were fed a regular diet or 30% less of the same diet, thus maintaining adequate nutrition but decreasing the number of calories consumed. Ten to fourteen years later (ten years! I sincerely hope this wasn’t a grad student’s project) the T cells of both sets of monkeys were assayed for T cell receptor repertoire diversity, memory T cell cytokine production, and T cell function.

Monkeys maintained on a CR diet had higher levels of not only phenotypically, but functionally naïve T cells with broad TCR diversity. This finding defines a potential mechanism of CR-mediated life extension – a low calorie diet can delay the onset of immune senescence, thereby preserving the ability to fight off infection in old age.

Notably, the authors failed to discuss the emotional state of the calorie-restricted monkeys – were they the unhappiest and crankiest monkeys of all time? I suspect so. The study raises an interesting question – what is the worth of long life if you can’t enjoy it to its fullest extent? For me, food and eating are much more than life-sustaining activities – I consider them full-blown hobbies. Am I doomed to a senescent immune system and life-threatening strep infections? I really don’t know. Am I willing to drastically change my current lifestyle for a benefit 30 years from now? In my naïve youth, I am inclined to say no. I think I would rather keep eating the things I love (within reason – I am not talking about foie gras for breakfast… maybe for lunch) while exercising and waiting for fellow scientists to dissect the mechanism of calorie restriction enough to make it into a pill. I figure they have a couple of decades to figure it out.