The Mediterranean diet has already been shown to help protect the aging brain and can significantly reduce the risk of heart disease. A new study has now found a much stronger link than previously realized between the Mediterranean diet — which is rich in whole grains, fish, fruit and olive oil — and a reduced risk of type 2 diabetes.
Previous research on the impact of a Mediterranean diet on diabetes has shown mixed results, perhaps because the studies were based on participants who self-remembered and reported the type of food they ate.
For the new research, published Thursday in PLOS Medicine, British scientists used blood samples to develop a biomarker scoring system. They first conducted a small study, called the Medley trial, with 128 adults ages 65 and older who were randomized to eat the Mediterranean diet or continue eating as they usually did over a six-month period.
A comparison of the two groups’ blood samples revealed a number of biomarkers of fatty acids and carotenoids, the substances that give color to vegetables such as pumpkins, carrots and tomatoes.
For the second part of the research, scientists from the University of Cambridge in the UK analyzed data, including blood samples and self-reported diet information, from more than 340,000 middle-aged participants in a long-running European study. In about 10 years, 9,453 had developed type 2 diabetes.
Then the researchers compared the biomarker scores from 9,453 to 12,749 randomly selected participants without diabetes in the large study.
They found an almost 30% reduction in diabetes risk using biomarker data, compared with a 10% reduction from self-reported data. This means that previous studies likely underestimated the impact of the Mediterranean diet.
The findings strengthen the possibility of recommending the Mediterranean diet for type 2 diabetes prevention, said senior author Dr. Nita Forouhi, professor of population health and nutrition and program leader in nutritional epidemiology at the University of Cambridge .
“The 20 percent of participants with the highest biomarker score values had a 62 percent lower risk of new-onset type 2 diabetes compared with the 20 percent with the lowest biomarker score values,” Forouhi said in a report. e-mail.
What is a Mediterranean Diet?
For someone consuming an average of 2,000 calories a day, researchers defined that as at least:
- 2 or 3 tablespoons of olive oil.
- Five portions of vegetables (75 g each).
- Two to three portions of fruit (150 g each).
- Five portions of cereal products (between 30 and 120 g each depending on the specific product).
And a daily maximum of:
- A medium potato.
- A portion of milk (250 ml).
- Two glasses of red wine (150 ml each).
Weekly recommendations included:
- Six servings of low-fat Greek yogurt (170 g each).
- One to three portions of poultry (100 g each).
- At least five servings of walnuts (35 g each).
- At least three portions of legumes (75 g each).
- At least three portions of fish (150 g each).
And a maximum of:
- Four portions of cheese (40 g each).
- A portion of red meat (100 g).
- Five eggs.
Dr Peter Goulden, head of the division of endocrinology, diabetes and bone diseases at Mount Sinai Morningside and Mount Sinai West, called the new biomarker an exciting development.
“If you compare the biomarker score to self-reports, the effect is three times greater,” said Goulden, who is also an associate professor at the Icahn School of Medicine at Mount Sinai. “So it’s very powerful.”
More studies will be needed to corroborate the findings and determine whether they would apply to a larger population, he said.
One drawback is that biomarkers don’t determine whether benefits come from fruit and vegetable consumption or some other aspect of the diet, said Linda Van Horn, a clinical nutrition epidemiologist at the Feinberg School of Medicine, Northwestern University in Chicago.
However, this approach “is more objective, so I would say it’s a step in the right direction,” he said.
The significance of the findings is underscored by rising rates of diabetes worldwide, said Dr. Anna Beth Bradley, assistant professor of medicine, diabetes, endocrinology and metabolism at Vanderbilt University School of Medicine.
“If you look at the prevalence of diabetes globally, you see that in Europe the incidence is around 6% to 7%, while in the US it is around 11%, which suggests that the American diet standard probably contributed to the rise in diabetes,” Bradley said. “That terrible American diet is spreading to other countries with diabetes on the rise in virtually every country.”