1. Department of Nutritional Sciences, University of Toronto, Toronto, ON M5S 3E2 Canada
2. Arnold School of Public Health, University of South Carolina, Columbia, SC 29208
3. School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900
4. Division of Public Health Sciences, School of Medicine, Wake Forest University, Winston-Salem, NC, 27157-1063