Do you want to live longer? Some recent research may have taken you one step closer to this. Researchers have known for years that they could extend the lives of species, from yeast to rodents, by restricting their food intake. But the mechanism has remained mysterious. Recently, a team led by molecular biologist Leonard Guarente of the Massachusetts Institute of Technology, USA, has identified what may be a biochemical link between calorie restriction and increased life span, at least in yeast. In a recently published study, the researchers report that the link appeared during studies of a phenomenon called 'silencing' that turns genes off at a particular chromosomal region and helps maintain the structural integrity of the DNA. They found that Sir2, a protein needed for silencing in yeast, and a chemical called NAD work together when the calorie intake is restricted. When food is restricted, concentrations of available NAD could rise, which could then boost Sir2's silencing activities to help cells live longer, Guarente proposes ( Science , Vol 287, No 5456).