A new study suggests a diet with the correct balance of proteins is more important than cutting calories when it comes to longevity.

Researchers at the Institute for Healthy Ageing at University College London looked at the effects of different diets on female fruit flies.
The flies were fed a steady diet of yeast, sugar and water with varying amounts of other nutrients like vitamins, lipids and amino acids.

The study’s results, published in the journal Nature, found that varying amounts of amino acids – which form the basis of proteins – were linked to both increased lifespan and fertility. Altering other nutrients did not affect either significantly, according to researchers.

They say their findings prove that it is possible to extend a person’s lifespan by balancing protein intake without cutting overall calories. "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," said study author Dr Matthew Piper.

Protein is available in nutritional supplement form as well as in foods like meats, soy and dairy products. However, researchers involved in the study say the amino acid methionine is the most advantageous when selecting protein sources. Foods high in methionine include sesame seeds, Brazil nuts, wheat germ, fish and meats.