Eat less for a longer life

Researchers have found that cutting down on calories can reduce the risk of age-related diseases.

Cutting back on the calories may help us live longer and improve our minds.

Scientists are often accused of having a God complex - and small wonder, given their apparent determination to find new twists on everything from human reproduction to weapons of mass destruction. Now they seem to be closing in on one of the defining characteristics of gods: immortality. A team of researchers in the US has just published a long-term study of an anti-ageing technique said to cut dramatically the risk of age-related diseases such as cancer and slow the ageing process. Better still, the technique is cheap and simple to use, and could be taken up right now by pretty much anyone in good health.

The bad news is that it means eating less - much less. Reporting their results in the current issue of the journal Science, the team claims that rhesus monkeys whose calorie intake was cut by 30 per cent did far better in later life than those allowed to eat whatever they liked. Study leader Professor Richard Weindruch of the University of Wisconsin-Madison, reported that the incidence of cancerous tumours and cardiovascular disease in monkeys on calorie-restricted diets was cut by over 50 per cent, while diabetes - common in monkeys that can eat all they want - had yet to be seen in any of those on the calorie-controlled diet.

Intriguingly, the age-related conditions did not merely emerge at a slower rate with these monkeys. By the time they reached the equivalent of "retirement age", the risk of such conditions stopped increasing, staying fixed at a much lower level than that faced by their free-eating counterparts. Nor were the benefits purely physical: the low-cal monkeys also had brains in better condition, with the regions responsible for motor control, short-term memory and problem-solving all better preserved.

To cap it all, the monkeys also lived longer. Since the beginning of the study in 1989, just 13 per cent of the monkeys on the restricted diet have succumbed to age-related diseases, compared to 37 per cent of those allowed to eat what they liked. All very exciting, but what the scientists omit to mention is what percentage of the long-living monkeys were happy with their lot. They certainly looked a lot healthier, with brighter eyes and bushier tails, but so do many otherwise miserable former Hollywood stars.

For those of us who don't fancy spending the rest of our lives picking at salads, another discovery announced last week seems more enticing: a compound that seems to slow ageing. The idea of popping a pill to buy more years sounds like science fiction, but that is the aim of a programme set up by the US National Institute of Ageing. Now it has made its first breakthrough, having identified a molecule which appears to boost the lifespan of mice.

Known as rapamycin, the compound is secreted by bacteria discovered over 30 years ago in soil samples from Easter Island. Since then it has been used with patients receiving transplanted organs, damping down their immune system to combat the risk of rejection. But it has also attracted the interest of anti-ageing researchers, because of its effect on an enzyme codenamed mTOR, which seems to play a role in the ageing process.

Now rapamycin has been put through the NIA's screening process, with dramatic results. According to the current issue of the journal Nature, when the compound was given to 600-day old mice -equivalent in human terms to around 60 years - their life expectancy was boosted by 28 per cent for males, and 38 per cent for females. That's roughly equivalent to adding an extra 6 years to the lives of elderly humans.

Anyone thinking of dashing off to Easter Island armed with a spade should think again, however. The results have some odd features - not least the fact that the mice given rapamycin seemed to be doing better than average even before they were fed the compound. That suggests that at least part of the improvement could be down to something else, such as better nutrition. Even if the results are replicated, rapamycin's powerful effect on the immune system rule it out as a practical anti-ageing compound. In any case, the results are based on experiments with mice - and all too many "breakthroughs" in animal experiments fail to work in humans.

The real significance of the study is that, despite appearances, it ties neatly with the findings from the experiment involving monkeys. Biochemists have found that the enzyme targeted by rapamycin, mTOR, is also affected by calorie intake - precisely the factor controlled in the monkey study. They have also discovered that mTOR affects processes inside living cells which leads to their steady deterioration over time ? in other words, ageing.

This suggests that by giving the mice rapamycin, the researchers were mimicking the effect of what a low-cal diet does far more simply: restricting the effect of mTOR. That, in turn, points to a strategy for developing a genuine anti-ageing pill: find a compound which targets mTOR without producing a host of unwanted side-effects. Given the complexity of the ageing process on mind and body, finding such a compound is likely to prove a huge challenge. Yet success is also likely to prove extremely lucrative, given international concern about coping with an growing population of people who are not just old but also infirm.

In the race to discover the elixir of middle age if not youth, let us hope that researchers don't forget the need to preserve spirit as well as mind and body. For as the late author Kingsley Amis pointed out, there are no pleasures in life worth giving up in exchange for a few more years in a nursing home. Robert Matthews is a Visiting Reader in Science at Aston University, Birmingham, England