FRIDAY, May 30 (HealthDay News) -- Adhering to the so-called Mediterranean diet, which is rich in fruits and vegetables and low in animal products, may protect you against developing type 2 diabetes, a Spanish study suggests.

A Mediterranean diet is often recommended as a way to guard against cardiovascular disease, but whether it protects against diabetes hasn't been established. The diet emphasizes olive oil, vegetables, fruits, nuts, cereals, legumes and fish, and deemphasizes meat and dairy products.

"The Mediterranean diet is a healthful eating plan that seems to help in the prevention of heart disease," said Connie Diekman, director of university nutrition at Washington University in St. Louis, who was not involved with the study. "Consumption of the Mediterranean diet will support health and may aid in the prevention of several diseases," she added.

For the study, published online May 30 in the British Medical Journal, researchers tracked the diets of 13,380 Spanish university graduates with no history of diabetes. Participants filled out a 136-item food questionnaire, which measured their entire diet (including their intake of fats), their cooking methods and their use of dietary supplements.

During an average of 4.4 years of follow-up, the team found that people who adhered to a Mediterranean diet had a lower risk of developing type 2 diabetes. In fact, those who stuck very closely to the diet reduced their risk by 83 percent.

Moreover, the people who tended to stick closest to the diet were those with factors that put them at the highest risk for developing diabetes, such as being older, having a family history of diabetes and being an ex-smoker. These people were expected to have a higher rate of diabetes, but when they adhered to the Mediterranean diet this was not the case, the researchers noted.

Type 2 diabetes is typically brought on by poor eating habits, too much weight and too little exercise.

The researchers suggested that one key factor that might be responsible for the protective effect of the Mediterranean diet is its emphasis on olive oil for cooking, frying, putting on bread and mixing in salad dressings.

"Our prospective cohort study suggests that substantial protection against diabetes can be obtained with the traditional Mediterranean diet, rich in olive oil, vegetables, fruits, nuts, cereals, legumes, and fish but relatively low in meat and dairy products," the researchers concluded.

Diekman said the study does have some limitations. "The use of food-frequency questionnaires is a limitation to actual intake, since most people don't know their real eating patterns and tend to 'guess' rather than provide real data," she said.

The low number of cases of diabetes identified in the study is another concern because typical demographic trends would suggest a higher number, she said.

"Finally, since the study is observational, it is hard to determine if other factors may have had an impact," Diekman said. "Self-reporting of study factors always compounds outcomes."

Still, another nutrition expert said the findings seem to confirm the benefits of a Mediterranean diet for overall health.

"This study reminds me of a comment I once heard someone else say -- 'Research simply confirms what we already know or suspect,' " said Lona Sandon, an assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center at Dallas and a spokeswoman for the American Dietetic Association.

"There are reams of epidemiological studies that have shown an association of the Mediterranean eating pattern with better health overall," Sandon said. "This study adds more fuel to the argument to make better choices in the types of fats we choose to eat and adding more vegetables to our plates."

More information

To learn more about the Mediterranean diet, visit the American Heart Association.

SOURCES: Connie Diekman, M.Ed, R.D., director, university nutrition, Washington University, St. Louis; Lona Sandon, R.D., assistant professor of clinical nutrition, University of Texas Southwestern Medical Center at Dallas, and spokeswoman, American Dietetic Association; May 30, 2008, British Medical Journal, online

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