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A Mediterranean diet low in carbohydrates may protect against type 2 diabetes, according to a new study.

The study involved 22,295 Greek participants who are part of the ongoing European Prospective Investigation into Cancer and nutrition (EPIC). Study results revealed that there were a total of 2,330 cases of type 2 diabetes. 

All participants filled out questionnaires on dietary habits, and researchers constructed a 10-point Mediterranean diet score (MDS) and a similar scale to measure the available carbohydrate (or glycaemic load [GL]) of the diet.

The findings revealed that people with an MDS of over 6 were 12 percent less likely to develop diabetes than those with the lowest MDS of 3 or under. However, participants with the highest available carbohydrate in their diet were 21 percent more likely to develop diabetes than those with the lowest.

Those with the highest DMS combined with the lowest available carbohydrate levels were 20 percent less likely to develop type 2 diabetes than those with a diet low in DMS and high in GL.

"The role of the Mediterranean diet in weight control is still controversial, and in most studies from Mediterranean countries the adherence to the Mediterranean diet was unrelated to overweight," researchers wrote in the study.

"This suggests that the protection of the Mediterranean diet against diabetes is not through weight control, but through several dietary characteristics of the Mediterranean diet. However, this issue is difficult to address in cohort studies because of the lack of information on weight changes during follow-up that are rarely recorded," they explained.

A particular feature of the Mediterranean diet is that it uses extra virgin olive oil, which leads to a high ratio of monosaturated to saturated fatty acids. However, research on this topic has been conflicting. Previous studies suggests that replacing saturated and trans fat with unsaturated fats has beneficial effects on insulin sensitivity and is likely to reduce the risk of type 2 diabetes. However, another study on high-cardiovascular-risk individuals revealed no differences between participants who were assigned to either free extra virgin olive oil or nuts Mediterranean diet and those on a low-fat diet.

Ultimately, people looking to protect their health should watch the amount of carbohydrates they consume. 

"High GL diet leads to rapid rises in blood glucose and insulin levels. The chronically increased insulin demand may eventually result in pancreatic β cell failure and, as a consequence, impaired glucose tolerance and increased insulin resistance, which is a predictor of diabetes. A high dietary GL has also been unfavourably related to glycaemic control in individuals with diabetes," researchers explained.

"A low GL diet that also adequately adheres to the principles of the traditional Mediterranean diet may reduce the incidence of type 2 diabetes," they concluded.

The findings are published in the journal Diabetologia.