1. Institute of Nutrition of Central America and Panama, Apartado Postal 1188, Guatemala, Cornell University, Ithaca, NY 14853-6301
2. Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853-6301
3. Department of Nutrition, University of Montréal, C. P. 6128, succursale A, Montréal, Québec, Canada H3C 3J7