The NHANES III cohort and DNA sample collection have been previously described.7 Briefly, NHANES III is a representative, cross-sectional sample of the non-institutionalized U.S. population surveyed between 1988 and 1994 by the National Center for Health Statistics (NCHS) at the Center for Disease Control and Prevention (CDC). Minority groups (non-Hispanic blacks and Mexican Americans), children, and the elderly were over sampled. The survey consisted of a household interview, including a detailed dietary questionnaire. In addition, a physical examination was performed, and blood samples were collected. For the genetic component of NHANES III, DNA was isolated from cell lines created from human blood samples from participants of NHANES III phase 2 (1991–1994). The total number of participants in NHANES III phase 2 was 16,530. DNA was available from 7157 of these individuals aged 12 and older.7 The present study was approved by the CDC Ethics Review Board and the institutional review board at the Massachusetts Institutes of Technology, and all subjects provided written informed consent.
