1. From the Departments of Nutrition (L.d.K., V.S.M., E.B.R., W.C.W., F.B.H.) and Epidemiology (E.B.R., W.C.W., F.B.H.), Harvard School of Public Health; Department of Laboratory Medicine, Children's Hospital Boston, Boston MA (L.d.K., M.D.K.); and Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (E.B.R., W.C.W., F.B.H.).