A different perspective.......
Sign in to read: How to live to 100... and enjoy it - health - 03 June 2006 - New Scientist
How's this for an elixir of youth: an X-ray, a mild case of sunburn, a couple of beers and a sauna. If you think all that would leave you feeling anything but youthful, think again. Many researchers believe that small doses of "stressors" such as poisons, radiation and heat can actually be good for you - so good that they can even reverse the ageing process. This counter-intuitive effect, called "hormesis", was once considered flaky, but in recent years it has been shown to extend longevity in yeast, fruit flies, protozoans, worms and rodents. If the findings extend to people, it could stretch the average healthy human lifespan to 90, says biologist Joan Smith-Sonneborn of the University of Wyoming in Laramie.
How so? Stressors seem to kick-start natural repair mechanisms, including heat-shock proteins and DNA-repair enzymes, to fix the damage they have caused. If this damage is not too severe, the repair systems may overcompensate, building up enough oomph to repair unrelated damage as well. And if you accept the idea that damage equals ageing, this is nothing less than rejuvenation.
There is already some indirect evidence that hormesis has positive effects on human longevity. Between 1980 and 1988, researchers at Johns Hopkins University in Baltimore, Maryland, tracked 28,000 nuclear shipyard workers to study the effects of low doses of radiation. To their surprise, they found that the mortality rate of these workers was 24 per cent lower than in a control group of 32,500 shipyard workers of similar ages who were not exposed to radiation.
An earlier study by legendary epidemiologist Richard Doll found similar low death rates among radiologists, compared with other doctors. Perhaps most strikingly, Barbara Gilchrest of Boston University has shown that feeding fragments of DNA to elderly human cells grown in culture, which mimics the effect of DNA damage, restores their DNA repair capabilities to levels usually seen only in youthful cells.
You may not even have to expose yourself to poisonous chemicals or radiation to see the benefits of hormesis. An increasing number of gerontologists think caloric restriction - the near-starvation diet that is the only reliable way so far of increasing lifespan in animals - works because it is a low-level stressor. Better yet, some compounds with supposed anti-ageing properties, notably vitamin E and melatonin, seem to act hormetically in protozoans: increasing longevity when taken in small amounts but not large ones.
The big unanswered question is at what dose does an otherwise harmful agent become beneficial. Clearly, too much radiation or poison are bad for you. However, there may be a safe way to trick your body's repair mechanisms into overdrive. Smith-Sonneborn and others suspect that the life-extending effects of exercise are also down to hormesis. She proudly practises what she preaches with an exercise regime that she says stresses her body to just the right level to get the optimum response. "I'm 70 and I have the bone density of a 35-year-old," she says.