Can a vegan or vegetarian diet help people treat their diabetes, or at least have a positive effect on them? Why?
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).
Not only has it been proven that a whole food plant-based diet can reverse diabetes type 2 in many cases, but that it can completely reverse diabetes type 2 in two weeks in some people who've been injecting themselves with insulin for 20 years on a daily basis. Studies where this has been achieved can be found at the following link: NutritionFacts