Eating such meals helps keep people healthy and wards off type 2 diabetes, which is linked to lifestyle factors like diet and obesity.
People who stuck strictly to a Mediterranean diet had an 83% lower chance of developing diabetes than those who did not, the study found.
Even those who kept to the diet at a moderate level had a 59% reduced risk of getting the disease.
Around 1.8 million people in the U.K. have Type 2 diabetes, and another 750,000 are thought to be undiagnosed.
The Mediterranean diet is traditionally low in meat and dairy products.
This research, published online in the British Medical Journal (BMJ), adds to the growing body of evidence on the protective effect of a Mediterranean diet.
Previous studies have shown that it can help ward off heart disease, asthma in children and help people live a longer life.
Researchers followed 13,380 graduates of the University of Navarra in Spain -- who did not have diabetes at the start of the study -- for an average of 4.4 years.
The students filled in questionnaires on how often they ate foods from a list of 136 different types.
They were also asked about their use of fats and oils, cooking methods and dietary supplements.
Every two years, they answered follow-up questionnaires on diet, lifestyle, risk factors and medical conditions.
New cases of diabetes during the study were confirmed through medical reports and additional, detailed questionnaires.
During the follow-up period of the study, 33 new cases of type 2 diabetes were confirmed.
All the participants were scored according to their daily intake of foods associated with the traditional Mediterranean diet.
This is defined as a diet with a high ratio of monounsaturated: saturated fatty acids, moderate intake of alcohol, high intake of legumes, high intake of grains, high intake of fruit and nuts, high intake of vegetables, high intake of fish, low intake of meat and meat products and moderate intake of milk and dairy products.
The study's findings were strengthened by the fact that people who stuck to the diet and achieved best results were those who would traditionally be most at risk of getting diabetes.
Yet the diet appeared to offer them protection, the authors said.
They wrote, "Interestingly, among participants with the highest adherence to the diet, there was a high prevalence of important risk factors for diabetes, such as older age, higher BMI, family history of diabetes, and personal history of hypertension and a higher proportion of ex-smokers.
"Therefore, we would have expected a higher incidence of diabetes among these participants.
"These higher risk participants with better adherence to the diet, however, had a lower risk of diabetes, suggesting that the diet might have a substantial potential for prevention."
The authors called for further research because little is known about the impact of the diet on diabetes. However, there is already some evidence suggesting it can protect against diabetes.
"The major protective characteristics include a high intake of fiber, a high intake of vegetable fat, a low intake of trans fatty acids, and a moderate intake of alcohol," the authors said.
"Moreover, a particular feature of the diet is the abundant use of virgin olive oil for cooking, frying, spreading on bread, or dressing salads.
"This leads to a high ratio of monounsaturated fatty acids to saturated fatty acids.
"Diets rich in monounsaturated fatty acids improve lipid profiles and glycaemic control in people with diabetes, suggesting that a high intake improves insulin sensitivity."
In conclusion, the authors wrote, "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."
Dr. Iain Frame, director of research at Diabetes UK, said, "The results of this research come from an observational study, so they are dependent on participants providing accurate information to the researchers.
"Although it is interesting that the researchers conclude that a Mediterranean diet could provide protection against type 2 diabetes, more robust research is needed before we can draw any firm conclusions about this claim.
"A fundamental link between being overweight and developing type 2 diabetes has already been proven.
"Diabetes UK advises people to follow a healthy diet low in fat, sugar and salt with plenty of fruit and vegetables, and to take regular physical activity to reduce the risk of developing the condition."
From the June 9, 2008, Prepared Foods e-Flash