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A TRADITIONAL Mediterranean diet high in vegetables, olive oil and nuts can cut the risk of diabetes by half in patients at high cardiovascular risk, independent of weight loss or boosted physical exercise, a new study shows.(1)
But Australian experts have warned doctors not to abandon strategies to encourage a healthy weight and more physical activity in favour of a Mediterranean diet because these strategies have also been shown in other studies to lower the risk of diabetes.
However, one expert says the study does show that medical practitioners did not have to stick to the one-diet-fits-all approach that currently dominates the management of people at risk of diabetes.
The study, reported in Diabetes Care, tested the effects of the traditional Mediterranean diet, characterised by a high consumption of vegetables, legumes, grains, fruits, nuts and olive oil, a moderate consumption of fish and wine, and low consumption of red and processed meat and whole-fat dairy products.
The trial involved 418 non-diabetic community-dwelling subjects aged 55–80 years who were randomised to a low-fat diet (control group), the Mediterranean diet supplemented with 1 L/week of virgin olive oil provided free, or the Mediterranean diet supplemented with mixed nuts (30 g/day), also provided at no cost.
There were no calorie restrictions and physical activity was not promoted.
During the study, 54 people developed new-onset diabetes.
After a median follow-up of 4 years, diabetes incidence was 17.9% in the control group, compared with only 10.1% in the Mediterranean diet with olive oil group and 11% in the Mediterranean diet with nuts group.
When the results of the two Mediterranean diet groups were merged, risk reduction was 52% and occurred without significant changes in body weight or physical activity.
In all groups, the study showed that the higher the adherence to the Mediterranean diet, the lower the incidence of diabetes.
Professor Jennie Brand-Miller, Professor of Human Nutrition at the University of Sydney, said the study results were a good outcome because they meant flexibility.
“The take home message is that a low-fat diet should not be the default diet, or the one-diet-fits-all approach that dominates clinical thinking, for diabetes and CVD protection,” she said.
Professor Brand-Miller said there was mounting evidence that healthy diets with more good fat, more good protein and fewer carbohydrates, with a lower glycaemic index, were superior.
The study authors said because chronic low-grade inflammation is a pathogenic factor in diabetes, anti-inflammatory properties of food in the Mediterranean diet, particularly in virgin olive oil and nuts, might be relevant to diabetes risk reduction.
“Education of the population on the MedDiet might be a safe public health approach to delay or prevent development of diabetes, as well as that of other prevalent chronic diseases,” the authors said.
Dr Joey Kaye, head of endocrinology and diabetes at Sir Charles Gairdner Hospital in Perth, said there was already good evidence for the Mediterranean diet for other metabolic conditions and cardiovascular disease.
“This study does argue that there is something in the composition of the Mediterranean diet, or something absent in the low-fat diet of the control group, that has an effect on insulin resistance or other mechanisms that will increase one’s risk of developing diabetes, whether that is inflammatory pathways, or gut peptides,” he said.
The study was interesting because there was an absence of change in weight, Dr Kaye said.
“Presumably there is something in the composition of the diet that is independent of total calories or independent of change in weight that will influence progression to diabetes,” he said.
However, weight loss and increased physical activity should not be abandoned, because they had been shown previously to reduce the risk of diabetes, he said.
Professor Brand-Miller said diet remained the key because every meal was a metabolic “stress test”.
1. Diabetes Care 2010; doi: 10.2337/dc10-1288.
Posted 25 October 2010