1. Research Institute; California Pacific Medical Center; San Francisco CA USA
2. Department of Epidemiology and Biostatistics; University of California; San Francisco San Francisco, CA USA
3. Department of Medicine; Brigham and Women's Hospital; Harvard Medical School; Boston MA USA
4. Vitamin Metabolism Laboratory; Jean Mayer United States Department of Agriculture (USDA) Human Nutrition Research Center on Aging at Tufts University; Boston MA USA
5. Institute of Biochemistry; Food and Nutrition Science; The Robert H. Smith Faculty of Agriculture Food and Environment; The Hebrew University of Jerusalem; Jerusalem Israel
6. Department of Medicine; University of California; San Francisco San Francisco, CA USA
7. Department of Family Medicine & Public Health; University of California; San Diego San Diego, CA USA
8. Department of Internal Medicine; University of California; San Diego San Diego, CA USA