Posted by: 4pack | December 3, 2009

“Ideal Diets”: Lower-Calorie Diets With A Healthy Mix Of Proteins Could Help Lengthen Lifespan


A diet containing just the right mix of proteins could be one of the keys to a long and healthy life, according to new research with fruit flies.

Scientists have discovered that manipulating the amount of a protein building-block eaten by fruit flies can extend their lifespans, without having knock-on effects on other physiological functions such as fertility.

Although the effect has yet to be identified in mammals such as mice, it promises to shed light on the biological pathways involved in human ageing. The hope is that it could eventually prove possible to manipulate these with drugs to allow people to live longer.

Research into the ageing process has previously identified that severely restricting food intake, so that only just enough calories are consumed to avoid starvation and malnutrition, can increase lifespans in organisms including nematode worms, fruit flies, mice and monkeys.

It is unclear, however, whether this effect applies to people, and it is unlikely to be a practical option. The diets involved are so minimal that they would be very difficult for people to maintain, and they also have a side-effect of suppressing fertility in animals.

The new research, by a team at the Institute of Healthy Ageing at University College, London, suggests that it could be possible to reap similar benefits from a much fuller diet that avoids this risk, if it is balanced in the right way.

In the study, published in the journal Nature, the scientists compared fruit flies fed several different diets. These varied in calorific value, and in their balance of vitamins, fats and amino acids — the building blocks of proteins.

They found that an amino acid called methionine had a particularly significant effect. When this was added to a low-calorie diet, the result was increased lifespan without decreased fertility. A reduced methionine intake in an otherwise full diet also had a similar effect.

“By carefully manipulating the balance of amino acids in the diet, we have been able to maximise both lifespan and fertility,” said Matthew Piper, a member of the study team. “This indicates that it is possible to extend lifespan without wholesale dietary restriction and without the unfortunate consequence of lowering reproductive capacity.”

Methionine is found at high levels in foods such as sesame seeds, Brazil nuts, wheat germ, fish and meat.

Dr Piper said it was too early to know what sort of diet might be most valuable, but that the research did raise questions over regimes high in protein, such as the Atkins diet.

“In the past, we have tended to think that the amount of protein is what is important to our diet,” he said. “We’ve shown here that in flies — and this is likely to be the case for other organisms — the balance of amino acids in the diet can affect health later in life. If this is the case for humans, then the type of protein will be more important.

“It’s not as simple as saying ‘eat less nuts’ or ‘eat more nuts’ to live longer. It’s about getting the protein balance right, a factor that might be particularly important for high-protein diets, such as the Atkins diet or body-builders’ protein supplements.”

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