1. INCAP/PAHO, Guatemala City, 11 Guatemala, C.A.
2. The Johns Hopkins University, School of Hygiene and Public Health, Center for Human Nutrition, Baltimore, MD 21205
3. National Institute of Public Health, 62508 Cuernavaca, Morelos, Mexico
4. International Food Policy Research Institute, Washington, D.C. 20036–3006
5. Department of Nutritional Sciences, University of California, Davis, CA 95616–8669