Researchers at Loma Linda University in California studied a group of healthy, non-diabetic people – 15,200 men and 26,187 women (17.3% blacks) – in the U.S. and Canada to determine associations between diet and diabetes. After collecting dietary and lifestyle data, the researchers divided the subjects into five groups: vegan, lacto-ovo vegetarian, pesco-vegetarian, semi-vegetarian, and non-vegetarian, then contacted all of them again after two years. They found that vegan, lacto-ovo and semi-vegetarian diets were protective against the development of diabetes, which had developed in 2.12% of non-vegetarians during this interval and that "in Blacks, the dimension of the protection associated with vegetarian diets was as great as the excess risk associated with Black ethnicity."
Nutrition, Metabolism, and Cardiovascular Diseases. October 7, 2011. [Epub ahead of print] (Tonstad et al.)