I'm wondering whether a diet rich in plant foods, such as a vegan diet, can have a positive impact on people with diabetes and/or people with pre-diabetes, the condition in which blood glucose levels are higher than normal but not high enough to be classified as full-blown diabetes.
There are several investigations assessing this issue. In several clinical trials (1, 2) Dr. Barnard has prooved that a low-fat vegan diet can improve serum values of HbA1c and requirements for medication of patients affected by type 2 diabetes. The same studies found significant improvements in plasma lipids (LDL and total cholesterols), that show decrease of risk factors for cardiovascular disease, often a complication of diabetes and metabolic disorders.
The reasons of the effectiveness must be found in the fact -among others- that vegetarians and vegans eat less quantities of total fats, saturated fats and highers amounts of fiber and show lower BMI (7).