1. Nutrition and Neurocognitive Laboratory, Jean Mayer Human Nutrition Research Center on Aging, Tufts University, 711 Washington Street, Boston, Massachusetts 02111, Brunswick Laboratories, 6 Thacher Lane, Wareham, Massachusetts 02571, and Agricultural Research Service, U.S. Department of Agriculture, Arkansas Children's Nutrition Center, 1120 Marshall Street, Little Rock, Arkansas 72202