A new study of the Max Planck Institute for Biology of Ageing could help to understand the positive effect of dietary restriction on healthy ageing. Previous evidence from different organisms (fruit flies and mice) have shown that dietary restriction increases longevity, but with a potential negative side effect of diminished fertility. So the female fruit fly reproduces less frequently with a reduced litter size on a low calorie diet, but its reproductive span lasts longer. This is the result of an evolutionary trait, as scientists believe: essential nutrients are diverted towards survival instead of reproduction. (Nature, December 3, 2009)
Researchers from the newly founded Max Planck Institute for Biology of Ageing in Cologne have studied whether health benefit stem from a reduction in specific nutrients or calorie intake in general by manipulating the diet of female fruit flies. The fruit flies were fed a diet of yeast, sugar and water, but with differing amounts of key nutrients, such as vitamins, lipids and amino acids. The scientists were able to show that longevity and fertility are affected by a combination of the type and amount of amino acids; whilst varying the amount of the other nutrients had little or no effect. Furthermore, the researchers found out in previous studies that levels of a particular amino acid – methionine – were crucial to increasing lifespan without decreasing fertility. By carefully manipulating the balance of amino acids, both lifespan and fertility were maximised. For the first time, this indicates that it is possible to extend lifespan without wholesale dietary restriction and without lowering reproductive capacity.
As the effects of dietary restriction on lifespan is evolutionary conserved – observed in different organisms – researchers believe that the essential mechanisms apply to it as well. Even though the human genome has about four times the number of genes as the fruit fly genome, there are many similarities on a genetic level, allowing these results to be of significance for humans as well.