Image caption Glass tubes containing powdered amino acids

A cocktail of amino acids - the building blocks of proteins - is the latest contender in the age-old search for the elixir of life.

Scientists gave mice drinking water laced with three amino acids. They said the rodents lived significantly longer than other mice fed a normal diet.

The research, reported in a scientific journal, has yet to be tried in people.

The study leader said a large patient trial was needed to provide evidence to convince doctors.

In experiments, middle-aged healthy male mice were given drinking water containing the amino acids leucine, isoleucine and valine.

Dr Enzo Nisoli, of the University of Milan, and colleagues, said it increased the average lifespan of the mice by 12% and boosted their fitness and co-ordination.

They wrote in their paper, published in Cell Metabolism: "Our study offers a rationale for deeply exploring the role of amino acids in prevention and control of age-related disorders in humans."

The amino acids - three of the 20 that make up proteins - have been shown to extend life span in yeast. However, the precise role of these amino acids in humans is unknown.

They are used by bodybuilders to maintain muscle tissue and can be bought in health food stores and online.