1. Vitamins and Carcinogenesis Laboratory
2. Department of Clinical and Experimental Medicine, Policlinico G.B. Rossi, University of Verona, 37134 Verona, Italy
3. Vitamin Metabolism Laboratory, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston MA 02111
4. Divisions of Clinical Nutrition and Gastroenterology, Tufts University School of Medicine, Boston, MA 02111