The cocktail of amino acids - building blocks of proteins - was found to increase the lifespan of mice by 12 per cent. Researchers believe it may also benefit humans, especially the elderly or sick. In laboratory experiments, middle-aged male healthy mice were given drinking water laced with three specific amino acids. The animals lived significantly longer than other mice fed a normal diet. Their lifespan range had a midpoint of 869 days compared with 774 days for untreated mice, a difference of 12 per cent.