• Eating a low glycemic load diet that also follows the principles of the traditional Mediterranean diet can lower type 2 diabetes risk.
• Point out that 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.

Eating a low glycemic load diet that also follows the principles of the traditional Mediterranean diet can lower type 2 diabetes risk, new research suggested.

People in the study whose eating patterns most closely adhered to the principles of the Mediterranean diet and the low glycemic load diet were 20% less likely to develop diabetes than people who least closely followed the two diets, Carlo La Vecchia, MD, of the Mario Negri Institute of Pharmacological Research in Milan, and colleagues, wrote online in the journalDiabetologia.

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.”

The study included residents of Greece participating in the ongoing European Prospective Investigation into Cancer and Nutrition (EPIC) trial, designed to investigate the impact of diet and lifestyle on the risk of diseases like cancer and diabetes.

Over 11 years of follow-up, 2,330 cases of type 2 diabetes were identified among 22,295 study participants.

All the participants completed a single, interviewer-administered food frequency questionnaire soon after enrolling in the study, and the responses were used by the researchers to develop a ten point Mediterranean diet score (MDS), with the number 10 reflecting the highest adherence to the diet.

The average daily glycemic load for each participant was arrived at by calculating the carbohydrate content per serving for each food listed, multiplied by the average number of servings of the food per day, multiplied by the food’s glycemic index.

A higher Mediterranean diet score (MDS) was found to be inversely associated with diabetes risk (hazard ratio 0.88 [95% CI 0.78-0.99] for an MDS of 6 or higher versus an MDS of 3 or lower.

Corresponding hazard ratios were 0.94 (95% CI 0.63-1.40) for body mass index of less than 25 kg/m² and 0.87 (95% CI 0.77-0.98) for BMI of 25 kg/m² or greater (p for heterogeneity 0.868). No heterogeneity was evident for age (P=0.560), sex (P=0.487), or level of physical activity (P=0.495).

Glycemic load was positively associated with a lower risk for diabetes (hazard ratio 1.21 [95% CI 1.05-1.40] for the highest versus the lowest glycemic load quartile).

“The influence of the Mediterranean diet against diabetes risk was independent of glycemic load levels, and individuals with a high MDS and a low glycemic load tended to have the lowest diabetes risk,” the researchers wrote. “It is not difficult to envisage a low glycemic load Mediterranean diet, since olive oil and vegetables dominate this diet and do not contribute, or contribute only marginally, to glycemic load.”

Registered dietitian Connie Diekman, M.Ed, RD, who is director of nutrition at Washington University in St. Louis, Missouri, said a major limitation of the study was the collection of dietary information through a single food-frequency questionnaire administered soon after participant enrollment.

But she added that the study supports other research finding the Mediterranean diet to be beneficial for people at risk for diabetes.

“If you look at the 2010 dietary guidelines for Americans, promoted in the ‘My Plate’ campaign, you really do see the Mediterranean diet,” she told MedPage Today.

“About half the plate is fruits and vegetables, a little over a fourth is grains and a little less than a fourth is proteins. That’s the equivalent of about half a cup or at most three-fourths of a cup of whole grain pasta or brown rice at a meal, which isn’t much. If the average American would fill half their plate with fruits and vegetables and limit portions of other foods, that would represent a huge step for lowering disease risk.”

• Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco
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