A study published on bmj.com reports that the traditional Mediterranean diet – one rich in olive oil, grains, fruits, nuts, vegetables, and fish, but low in alcohol, dairy, and meat products – protects individuals from type 2 diabetes (also known as adult-onset diabetes).

Previous research has shown that the traditional Mediterranean diet can provide protection from cardiovascular disease, but it is still unknown as to how the diet affects a healthy person’s risk of developing diabetes. To investigate this potential link, Spanish researchers conducted a prospective cohort study with over 13,000 graduates from the University of Navarra, Spain. The participants were recruited between December 1999 and November 2007 and had no history of diabetes. Their dietary and health habits were tracked by researchers during a follow-up period of about 4.4 years.

The baseline survey consisted of a 136 item food frequency questionnaire that was used to establish a measure of the entire diet. Participants also responded to questions regarding their use of fats and oils, cooking methods and dietary supplements. Follow-up questionnaires were sent every two years to collect data pertaining to diet, lifestyle, risk factors, and medical conditions. Medical reports provided information on new cases of diabetes.

The main finding was that participants who adhered closely to the Mediterranean diet had a lower risk of diabetes. Specifically, participants who adhered highly to the diet had an 83% relative reduction in risk of developing diabetes. The researchers also found it interesting that the participants who kept strict Mediterranean diets were the ones who were most susceptible to diabetes through risk factors such as older age, a family history of diabetes, and a history of smoking. Since this group was expected to have a higher incidence of diabetes, the authors suggest that their observed lower risk is indicative of the Mediterranean diet’s potentially substantial protective ability.

It was identified that a high intake of fiber and vegetable fat, a low intake of trans-fatty acids, and a moderate intake of alcohol were the major protective characteristics of the diet. An important element, the authors note, is the generous use of virgin oil for cooking, frying, spreading on bread, and in salad dressings.

The authors conclude: “Our prospective cohort 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 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.”

Adherence to Mediterranean diet and risk of developing diabetes: prospective cohort study
MA Martınez-Gonzalez, C de la Fuente-Arrillaga, J M Nunez-Cordoba, F J Basterra-Gortari, J J Beunza, Z Vazquez, S Benito, A Tortosa, M Bes-Rastrollo
BMJ (2008)
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Written by: Peter M Crosta