A traditional Mediterranean diet rich in olive oil, vegetables and fish can drastically reduce the risk of getting type 2 diabetes, a new study says.

In a study of more than 13,000 people, Spanish researchers found that people who strictly adhered to the diet had an 83 per cent reduction in their risk of developing diabetes. Those who moderately followed the diet had their risk reduced by 59 per cent.

These findings were surprising to the researchers, given that those who followed the diet very closely also had the greatest factors for the disease, such as older age, a family history of diabetes and being an ex-smoker.

However, because their risk was so drastically reduced, the researchers assume that the foods that make up the diet itself have a role in warding off diabetes.

In their study, the authors point out that olive oil can protect against insulin resistance. Insulin is produced by the pancreas to help the body process sugar. As well, a diet high in fruits and vegetables can help reduce inflammation in the body, which is a risk factor for a number of illnesses.

The diet, which is also high in nuts, grains and fruit, but low in meat, alcohol and dairy products, is already known to protect against cardiovascular disease.

"Our study suggests that substantial protection against diabetes can be obtained with the traditional Mediterranean diet, rich in olive oil, vegetables, fruits, nuts, cereals, legumes, and fish but relatively low in meat and dairy products," the authors concluded.

"The limited number of cases of diabetes and the possibility of under-reporting, however, requires that further larger cohorts and trials are needed to confirm our findings."

The findings were published Thursday in the online edition of The British Medical Journal.

Abstract:

Adherence to Mediterranean diet and risk of developing diabetes: prospective cohort study

Objective To assess the relation between adherence to a Mediterranean diet and the incidence of diabetes among initially healthy participants.

Design Prospective cohort study with estimates of relative risk adjusted for sex, age, years of university education, total energy intake, body mass index, physical activity, sedentary habits, smoking, family history of diabetes, and personal history of hypertension.

Setting Spanish university department.

Participants 13 380 Spanish university graduates without diabetes at baseline followed up for a median of 4.4 years.

Main outcome measures Dietary habits assessed at baseline with a validated 136 item food frequency questionnaire and scored on a nine point index. New cases of diabetes confirmed through medical reports and an additional detailed questionnaire posted to those who self reported a new diagnosis of diabetes by a doctor during follow-up. Confirmed cases of type 2 diabetes.

Results Participants who adhered closely to a Mediterranean diet had a lower risk of diabetes. The incidence rate ratios adjusted for sex and age were 0.41 (95% confidence interval 0.19 to 0.87) for those with moderate adherence (score 3-6) and 0.17 (0.04 to 0.75) for those with the highest adherence (score 7-9) compared with those with low adherence (score <3). In the fully adjusted analyses the results were similar. A two point increase in the score was associated with a 35% relative reduction in the risk of diabetes (incidence rate ratio 0.65, 0.44 to 0.95), with a significant inverse linear trend (P=0.04) in the multivariate analysis.

Conclusion Adherence to a Mediterranean diet is associated with a reduced risk of diabetes.