The latest supplement from Nature contains a collection of articles on the topic of aging, largely from the mainstream research community viewpoint that centers on modestly slowing aging as a goal rather than anything more ambitious:
Humans are the longest lived primates, with life expectancy in some developed nations surpassing 80 years. Of course, that doesn't stop us wanting more time. Research into the mechanisms of ageing is yielding insights, many of them diet-related, into how we might not only live longer but also stay healthier as we do.
I'll point you to a couple of the more interesting pieces, which review some of the knowledge gained in recent years:
Comparative studies are beginning to give clues to the cellular and molecular mechanisms that enable some species to live longer than related species. Miller's team, for example, cultured skin cells from nine rodent species and exposed them to various stresses, including cadmium, hydrogen peroxide and heat. Similar experiments involved skin cells from 35 different bird species. Both studies showed that cells from long-lived animals are more resistant to stresses than those of short-lived species, says Miller.
Similar research also suggests one possible reason why birds tend to live longer than mammals of similar size, Miller adds. "Bird cells tend to be three- to ten-fold more resistant to many of these stresses than cells from rodents of the same size. We can't prove that's why birds live a long time, but it's a good guess."
While researchers wait for statistical proof of the diet's effects in primates, some people have elected to go on the diet anyway. CRONies - the label adopted by those on a diet of Caloric Restriction with Optimal Nutrition - voluntarily eat 30% fewer calories than recommended by the US Department of Agriculture. That can be as low as 1,400 calories a day for men, and 1,120 for women.
Fontana, who studies the CRONies, says most of the health benefits seen in animals on the caloric restriction diet also appear in humans. He says that people who started caloric restriction in middle age and stayed with the regimen for eight years have a "fantastic" cardiometabolic profile. He adds that he has seen subjects in their late 70s with the blood pressure of teenagers.
As with so much else, stem cells in an older person are not the same as those in someone younger. They tend to be less productive and less reliable, and become slower and less predictable when it comes to replenishing cells affected by injury, illness or senescence - and the tissues they serve become less healthy and vital. In other words, stem cells are prominent in the fundamental biology of ageing. If stem cells in older people could be made to retain their effectiveness, perhaps broken bones and skin wounds could be made to heal faster and, with time, we might be able to treat the conditions of old age, such as dementia and heart disease.