1. Department of Community and Family Medicine, Duke University Medical Center, Durham, North Carolina.
2. Department of Internal Medicine, Duke University Medical Center, Durham, North Carolina.
3. Department of Nutrition, University of North Carolina at Greensboro, Greensboro, North Carolina.
4. Duke Clinical Research Institute, Duke University Medical Center, Durham, North Carolina.
5. University of North Carolina School of Public Health, Chapel Hill, North Carolina.