Combo of Low GL, Mediterranean Diet Protective for Diabetes

August 15, 2013

A low-glycemic-load diet that also adheres to the principles of the traditional Mediterranean style of eating appears to reduce the risk for type 2 diabetes by about 20%, new prospective research shows. The report is published online August 15, 2013 in Diabetologia by Carlo La Vecchia, MD, from the Mario Negri Institute of Pharmacological Research, Milan, Italy, and colleagues.

"We know that a diet low in glycemic load is favorable for diabetes; this is more or less well established. The novelty of [our research] is that the Mediterranean diet is favorable on diabetes risk," Dr. La Vecchia told Medscape Medical News.

In addition, "a diet low in glycemic load with a high Mediterranean score seems to add to the favorable effect," he noted. And importantly, these entire findings stand after adjustment for multiple confounding factors, including body mass index (BMI), said Dr. Vecchia.

Asked to comment on the results, Libby Dowling, Diabetes UK clinical advisor, said the study "suggests that people who adopt a Mediterranean-style diet can also reduce their risk of type 2 diabetes." However, "while the Mediterranean diet can often be a healthy one, the evidence that it is particularly effective at reducing risk of type 2 diabetes is not conclusive," she cautioned.

"The best way to reduce your risk of developing type 2 diabetes is by losing any excess weight through increased physical activity and eating a healthy balanced diet," she added.

Reduction in Diabetes is Not Due to Weight Loss

The authors studied patients from Greece who are part of the ongoing European Prospective Investigation into Cancer and Nutrition (EPIC). From a total of 22,295 participants, actively followed up for just over 11 years, 2330 cases of type 2 diabetes were recorded.

To assess dietary habits, all participants completed a questionnaire, and a 10-point Mediterranean-diet score (MDS) was calculated, as well as the available carbohydrate (or glycemic load) score of the diet.

A higher MDS was inversely associated with diabetes, with a hazard ratio of 0.88 for an MDS of 6 or greater compared with an MDS of 3 or less.

Glycemic load was positively associated with diabetes (HR 1.21) for the highest vs the lowest quartile of glycemic load.

A high MDS combined with low glycemic load reduced the chances of developing diabetes by 20% as compared with a diet low in MDS and high in glycemic load.

The authors admit that the role of the Mediterranean diet in weight control "is still controversial. In most studies from Mediterranean countries, adherence to the Mediterranean diet was unrelated to overweight."

The new findings, together with prior ones, suggest that the protection of the Mediterranean diet against diabetes is not through weight control but perhaps through certain characteristics of the diet, such as the use of extra virgin olive oil, which leads to a high ratio of monounsaturated to saturated fatty acids, they speculate.

Meanwhile, high-glycemic-load diets lead "to rapid rises in blood glucose and insulin levels," they observe. "The chronically increased insulin demand may eventually result in pancreatic ß-cell failure and, as a consequence, impaired glucose tolerance and increased insulin resistance, which is a predictor of diabetes."

And a high dietary glycemic load has also been unfavorably related to glycemic control in individuals with diabetes, they observe.

But Ms. Dowling says while the study highlights that it is important for people to be aware of their portion size when eating carbohydrates, "we wouldn't recommend that people restrict their diet only to foods that have a low glycemic load, as this means they could miss out on essential nutrients."

The authors have reported no relevant financial relationships.

Diabetologia. Published online August 15, 2013. Abstract

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