Division of Epidemiology, Vanderbilt Ingram Cancer Center, Department of Medicine, Vanderbilt University School of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA. Division of Epidemiology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA. Department of Medicine, Marlene and Stewart Greenebaum Cancer Center, University of Maryland, Baltimore, MD, USA. Department of Medicine, Vanderbilt Center for Human Nutrition, Vanderbilt University Medical Center, Nashville, TN, USA. Departments of Nutrition and Epidemiology, Harvard School of Public Health, Boston, MA, USA. Division of Epidemiology, Vanderbilt Ingram Cancer Center, Department of Medicine, Vanderbilt University School of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA. qi.dai@vanderbilt.edu.