Calorie Restriction, longevity, and waiting for proof of what works

If a life-extension technology works well with yeast, fruit flies and nematodes, will it also work well with us humans?  It would take a very long time to prove this through controlled lifelong experiments.  And such experiments might never happen. 

We know of several things that experimentally extends the life spans of fruit flies and nematodes and a few things that demonstrably extend the life spans of mice and rats.  However, there is very little firm experimental evidence on what can for-sure extend the life spans of primates: apes and chimpanzees.  And no such experiments for humans.  This is because of the lengths of time required to measure fully the impacts of anti-aging interventions on life spans – a few days in the case of fruit flies, two years in the case of mice, 40 years in the case of many monkeys and 90 years in the case of humans. 

Calorie  restriction has long been known to be the most sure-fire intervention for achieving  life extension.  It has been shown to work for a number of primitive species and has been shown to confer up to 40% life extension for smaller animals like mice and rats.  Moreover, the associated genetic pathways are starting to be understood and are known to be similar across species including our own.  Some 20 years ago, two US research groups set out to show that calorie restriction works also for extending the lives of primates.  Yesterday, another interim report appeared that lends credence to this hypothesis, this time for rhesus monkeys.  Studying aging in monkeys takes a lot of patience.  “Mice and rats only live for a couple of years, while these monkeys can live to 40, and the average life span is 27 years. Now that the surviving monkeys have reached their mid- to late 20s, the Wisconsin group could glean how calorie restriction was affecting their life span. Sixty-three percent of the calorie-restricted animals are still alive compared to only 45% of their free-feeding counterparts. For age-related deaths caused by illnesses such as cardiovascular disease and cancer, the voracious eaters died at three times the rate of restricted monkeys: 14 versus five monkeys, respectively. Another seven control and nine lean monkeys died from causes not related to aging such as complications from anesthesia or injuries. Leaner diets also reduced muscle and brain gray matter deterioration, two conditions associated with aging. (The team has not yet studied cognitive differences between the two groups.) (ref).”

The indications are plain but the real bottom line won’t be in for the monkey study until another 10 years have passed. Then it would take another 80-90 years of the same kind of experiment  to prove that calorie restriction works to extend lives in humans. 

Calorie restriction is not to most people’s taste, so such an experiment will probably never happen.  Instead, we rely on other interventions to delay aging, such as taking resveratrol which is shown by studies to activate some of the same genetic pathways activated by calorie restriction.  We are relying on knowledge of underlying mechanisms of molecular biology, genomics, and the other “omics,” plus experimental results with small animals which we infer should apply more or less to us as well.  For those of us interested in life extension now, this is the best we can do. 500 years from now we should have much firmer evidence of what delays aging in people.  Personally, I strongly prefer not to wait for that before taking anti-aging actions.