1. Division of Human Nutrition, Dietetics and Foods; and Division of Hematology, Department of Medicine, University of Washington, Seattle, Washington 98195.
2. Department of Medicine, University of Goteborg, Goteborg, Sweden.
3. Department of Experimental Medicine, Instituto Venezolano de Investigaciones Cientificas (I.V.I.C.), Caracas, Venezuela.
4. Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts 02115.
5. Division of Hematology, Department of Medicine, University of Kansas Medical Center, Kansas City, Kansas 66103.
6. Vitamin and Mineral Nutrition Laboratory, U. S. Department of Agriculture, Beltsville, Maryland.