Mediterranean diet found to lower risk of developing Type 2 diabetes

Even without weight loss, adhering to a diet rich in fresh produce, chicken, fish and olive oil is 40 percent more effective in heading off the development of Type 2 diabetes than following a low-fat diet, a new study has found.

The research suggests that for the nation’s 78 million obese adults, a diet that minimizes red meat and sweets but incorporates plant-based fats may be a sustainable way to improve health, even if permanent weight reduction proves elusive.

The findings add to mounting research that suggests a traditional Mediterranean diet may be easier to adhere to and more likely to improve health than more restrictive regimens.

Compared with those on a low-fat diet, trial participants whose Mediterranean-style diet was supplemented with a daily dose of tree nuts – almonds, walnuts and hazelnuts – were 18 percent less likely to develop Type 2 diabetes. The researchers called that a positive trend but acknowledged that the difference fell short of demonstrating beyond doubt the superiority of such a diet over a standard low-fat diet.

Published in the Annals of Internal Medicine, the latest entry in the diet fray followed for more than four years a group of 3,541 older Spaniards who were at high risk of developing cardiovascular disease. They were a subgroup of a larger clinical trial that demonstrated the effectiveness of the Mediterranean diet in reducing the risk of heart attacks and strokes.

That trial of 7,447 subjects – documented in February in the peer-reviewed New England Journal of Medicine – found that those placed on a Mediterranean diet supplemented with either nuts or extra-virgin olive oil were 30 percent less likely than those prescribed a low-fat diet to suffer a heart attack, stroke or death due to cardiovascular disease.

Nearly half of those recruited for the parent trial already had Type 2 diabetes.

The subjects used in the current subgroup analysis started the trial with at least three risk factors for developing premature cardiovascular disease: They were active smokers; were overweight or obese; had a family history of premature heart disease; or had hypertension or worrisome cholesterol readings. None had been diagnosed with Type 2 diabetes at the start of the trial.

Of the participants, 273 went on to develop Type 2 diabetes. Among those in the Mediterranean diet-supplemented-with-extra-virgin-olive-oil arm, 6.9 percent developed diabetes; among those in the Mediterranean-diet-plus-nuts group, 7.4 percent did so; and among the low-fat dieters, 8.8 percent developed Type 2 diabetes.

Dr. Meir Stampfer, professor of medicine and epidemiology at Harvard University, called the research a significant step in further demonstrating the clinical benefits of the diet that until recently predominated in southern Europe. In showing the Mediterranean diet to be sustainable and beneficial, Stampfer said, the study should help put to rest many health-conscious Americans’ aversion to nuts and oils, as calorie-dense as they are rich in unsaturated fats.

But Dr. David Heber of the University of California, Los Angeles’ Center for Human Nutrition cautioned that Americans should not give up efforts to cut fat from their diets in a bid to improve health. He pointed to copious evidence supporting a widely available regimen known as the Diabetes Prevention Program: When people at risk for diabetes lose 5 percent to 10 percent of their body weight using a program that reduces calorie and fat consumption and boosts their exercise, they drive down the likelihood of developing diabetes over the next five years by close to 60 percent.

“Saying that it’s beneficial to consume more olive oil, which has over 100 calories per tablespoon, without weight loss encourages magical thinking about diabetes,” Heber added.

Dr. James Meigs, an internal medicine specialist at Harvard University, noted that the latest research suggests a Mediterranean diet drives down diabetes risk as much as preventive use of the drug metformin. But that’s still only half as powerful an effect as that seen in subjects participating in the Diabetes Prevention Program, which recommends at least 30 minutes a day of exercise and a low-fat, reduced-calorie diet.

Meigs said that while physicians still should advise obese patients to lose weight and exercise more, he sees “little harm of also encouraging” Mediterranean-style diets.