Hunger for long life: the ethics of caloric restriction experiments

This has been a good week for life extension research, with the Nature paper Rapamycin fed late in life extends lifespan in genetically heterogeneous mice by Harrison et al. (free News and Views) showing that the drug boosts lifespan in middle aged mice, and Science countering with Caloric Restriction Delays Disease Onset and Mortality in Rhesus Monkeys by Colman et al. showing that in a 20-year longitudinal study rhesus monkeys do seem to benefit from caloric restriction (CR). CR involves keeping the energy intake low, but not so low that it induces starvation.

Not everybody seems to like the experiment. The Swedish major newspaper Dagens Nyheter had an article by Per Snaprud
that appeared to criticise the monkey experiment on ethical grounds. He
quotes Mats Spångberg, chief veterinarian at the Swedish Institute for
Infectious Disease Control, who doubts the experiment would have been
approved in Sweden. The only use of monkeys in Swedish research is AIDS
vaccine research. The article concludes by stating that the virus kills
2 million people every year, 270,000 of whose are children.

But ageing kills 100,000 people worldwide each day directly or indirectly. 100% of humans and monkeys are "infected".

It should be noted that a few studies of caloric restriction in humans
have been done, as well as quasi-experiments like the frugal diet of
Okinawa. The mainproblem is that humans are so long-lived that it is hard to draw strong conclusions from them.
The real benefit from CR research will likely be a better understanding
of the mechanisms of ageing and possibly "CR mimetics", drugs that
trigger the same anti-ageing response as reduced food intake. Real CR is simpy too impractical for weak-willed humans in a world of culinary delights.

It might be factually true that caloric restriction monkey
experiments are unlikely to be approved in Sweden for cultural and institutional reasons, but ethically it
seems to me that the case for the experiment is strong. The need for
understanding and limiting the ravages of aging is enormous when
measured in lives lost (not to mention suffering and loss of human
capital). If one doesn't think it is worth finding ways of slowing or at least understand aging (as DN
journalist Hanne Kjöller seems to argue in an opinion piece today) if it
reduces the life quality of the monkeys, then one should give serious
consideration of not trying to find an AIDS vaccine either. After all,
it is a smaller problem.

The persistent hunger likely experienced by the monkeys is
presumably not too different from what monkeys would experience in the
wild where food access is haphazard. If the monkeys in the CR
experiment have lives worth living – which seems to be the case – the
extension of these lives adds value.

This is true even if the life quality
is somewhat lowered by hunger compared to monkeys who can eat as much as they like. It
seems unlikely that the value of the longer life and reduction of
illness can be completely offset by plain hunger (especially since older monkeys in the experiment with chronic conditions like diabetes get medical treatment). If one were to seriously believe chronic hunger to be so bad that it reduces
quality of life below worth living, one should give serious thought
about feeding as many wild animals as possible and kill the rest. Or invite them into the lab, where they would at least get medical treatment.

Many people suffer from scope insensitivity and the availability heuristic when it comes to ageing compared to other conditions. They do not see how much pervasive suffering it causes, and they put more emphasis on comparatively rarer causes of mortality that stand out. The result is that they try to justify the current situation, allowing the carnage to go on.