Olive oil and vinegar
And eating low glycemic load helps, too, according to an article at MedPageToday. The 22,000 Greek study participants were followed for 11 years. From the article:
The findings suggest that eliminating or strictly limiting high glycemic load foods such as those high in refined sugars and grains and following the largely plant-based Mediterranean diet, which emphasizes vegetables, fruits, nuts and legumes, can have a significant impact on diabetes risk, La Vecchia said.
“The impact of the diets was synergistic,” he told MedPage Today. “The message is that eating a largely Mediterranean diet that is also low in glycemic load is particularly favorable for preventing diabetes.”
Spanish researchers found the same thing a few years ago.
The Mediterranean diet is also healthy for those who already have type 2 diabetes.
The Low-Carb Mediterranean Diet may be the ideal way of eating for diabetics.
Diabetic Mediterranean Diet 