Kai Wang1, Mingyang Song1,2,3,4. 1. Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA. 2. Clinical and Translational Epidemiology Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA. 3. Division of Gastroenterology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA. 4. Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, USA.