The American Heart Association has joined the chorus of health experts calling for even lower limits on daily salt intake. In a new advisory, the association said all Americans should aim for no more than 1,500 milligrams of sodium daily. Previously, that guideline had been 2,300 mg, although people with high blood pressure, blacks and older individuals-groups totaling up to 70% of the population-were advised to limit daily sodium to 1,500 milligrams. In lowering its sodium target, the Heart Association cited more than 50 trials on the blood-pressure effects of salt, as well as benefits of sodium reduction in preventing the blood-pressure increases that come with aging-ultimately affecting 90% of adults. Experts acknowledge, however, that cutting sodium intake so low represents a challenge, especially since three-quarters of the sodium in the US diet comes not from the salt shaker but from processed foods.