Research: FRUIT-FLY DIETS AND LONGEVITY

Cut down a fruit fly's diet to half of its normal calories, and the average lifespan almost doubles. Similar effects are seen in a wide range of organisms, from yeast to mice, but it has been thought that it was calorie reduction in general, rather than the specific source of calories, that increases longevity.

Professor Linda Partridge and colleagues at University College

London have now found that, per calorie, different constituents of the diet have very different effects on lifespan, implying that the links between calorie restriction and longevity may be more complex than once thought.

In the lab, Drosophila are fed on a diet of yeast (contributing a mixture of nutrients including protein and fat) and sugar (carbohydrates), which provide roughly the same number of calories per gram. The researchers could therefore feed the flies on a yeast-restricted diet or a sugar-restricted diet with the same number of calories, and compare the effects on lifespan. They found that reducing either dietary yeast or sugar could reduce mortality and extend lifespan, but by an amount that was unrelated to the calorie content of the food – and yeast had a much greater effect per calorie than did sugar.

For fruit flies at least, the research suggests that it is not simply calorie intake that influences longevity, but also the specific nutritional make-up of the food. In which case, Professor Partridge and colleagues suggest, the full effect of dietary restriction on lifespan could be obtained by reducing critical nutrients in the food without reducing overall calorie intake.

External links

• Mair W et al. Calories do not explain extension of life span by dietary restriction in Drosophila. PLoS Biol 2005;3(7):e223.