Could Mediterranean diet prevent diabetes?

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People at risk for type 2 diabetes are often overweight or obese, and are counseled to lose weight to help prevent the disease. But a new study just published in the Annals of Internal Medicine suggests that weight loss isn t the only means of prevention diet might work too.

The research was led by Dr. Jordi Salas-Salado of the Faculty of Medicine and Healthy Sciences, Universitat Rovira i Virgili, C/ Sant Llorenç, Reus, Spain, and was a sub-analysis of data from the PREDIMED study in Spain.

The participants in this study were 3541 men and women between 55 and 80 years of age. None had diabetes at the beginning of the research, but all had elevated risk of cardiovascular disease (CVD) defined as current smoking, hypertension, hypercholesterolemia, low HDL (good cholesterol) levels, overweight, obesity, or family history of early CVD.

They were divided into 3 dietary groups. One group received dietary instructions to consume a Mediterranean type diet, consisting of 35-40 percent of calories from fat, and rich in olive oil and nuts and supplemented with extra virgin olive oil (EVOO). The second group also ate a Mediterranean diet, but one that was supplemented with walnuts, almonds and hazelnuts. The last group, the controls, was advised to reduce consumption of all types of fats, and received no dietary supplements.

Every three months, participants in the Mediterranean diet groups completed a 14-item dietary questionnaire, and on the basis of their responses were given individualized and group training sessions to help with adherence to the assigned plans. Similarly, the control participants completed a 9-item questionnaire, and received individualized advice. After a median follow-up period of about 4 years, the researchers evaluated the occurrence of new cases (incidence) of type 2 diabetes in each diet group.

They found that there was a substantial reduction in risk of diabetes in both groups on the Mediterranean diet compared to the low fat diet. It dropped by 40 percent in the EVOO-supplemented diet group, and by 18 percent in the nut-supplemented diet group, for an average reduction of 30 percent. The body weights of the three groups were the same, on average, at the beginning of the study, and the authors reported that there were no significant changes in any group over the course of the research.

The authors commented Given that there were no specific restrictions on energy intake or counsel to increase physical activity, the observed benefit is likely attributable to the Mediterranean diet plus the supplemental foods given for free. They also noted that diabetes incidence was not the primary endpoint of the overall study, which made their data exploratory in nature.

ACSH s Dr. Ruth Kava was intrigued by the results, saying These data provide some hope that individuals with risk factors for CVD can benefit substantially from a Mediterranean dietary pattern, without great attention to calorie intake. It remains to be seen, however, whether further research will support these conclusions, which would be needed before they can be relied upon.