She led the study, published in Thursday's New England Journal of Medicine. The National Institutes of Health and the International Tree Nut Council Nutrition Research & Education Foundation sponsored the study, but the nut group had no role in designing it or reporting the results.
Researchers don't know why nuts may boost health. It could be that their unsaturated fatty acids, minerals and other nutrients lower cholesterol and inflammation and reduce other problems, as earlier studies seemed to show.
Observational studies like this one can't prove cause and effect, only suggest a connection. Research on diets is especially tough, because it can be difficult to single out the effects of any one food.
People who eat more nuts may eat them on salads, for example, and some of the benefit may come from the leafy greens, said Dr. Robert Eckel, a University of Colorado cardiologist and former president of the American Heart Association.