1. U.S. Department of Agriculture, Agriculture Research Service, Arkansas Children's Nutrition Center, 1120 Marshall Street, Little Rock, Arkansas, U.S. Department of Agriculture Jean Mayer Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, Boston, Massachusetts 02111, and Analytical and Applied Sciences Group, Mars Incorporated, 800 High Street, Hackettstown, New Jersey 07840