Mediterranean Diet May Protect More Against Diabetes
The Mediterranean diet has been ranked as one of the best diets in the world because of the many healthy foods involved in the plan. Studies suggest that the Mediterranean diet, or MedDiet for short, helps to lower risk factors for heart disease, stroke, cognitive decline, and other serious health conditions. Now, new research provides a stronger link showing how the MedDiet effectively reduces the risk of type 2 diabetes.
The MedDiet is based on foods eaten by people living in what’s dubbed “Blue Zones,” five places in the world where people live the longest and healthiest: Loma Linda, California; Nicoya, Costa Rica; Ikaria, Greece; Sardinia, Italy; and Okinawa, Japan. Residents in these regions have a pattern of eating plant-based, low-carb, non-starchy foods that include:
• Whole grains
• Nuts and nut butter
• Oils rich in monounsaturated fats, such as extra virgin olive oil, canola oil, grapeseed oil
• Fish rich in omega-3 fatty acids
• Little to no meat, with poultry as the favorite option over red meat
• No sodas or sugary drinks
• A moderate amount of wine with meals
Previous research examining the effectiveness of the MedDiet on diabetes has shown mixed results, possibly because the studies relied on participants reporting the type of foods they were eating. Because self-reporting is subjective, the potential link between a MedDiet and type 2 diabetes risk had not been evaluated objectively.
However, a team of scientists from Europe and Australia provided stronger evidence by using objective biological indicators, also known as biomarkers, that associated the MedDiet with a lower risk of developing type 2 diabetes. The investigators measured how closely a person follows the MedDiet by using a blood test.
The first part of the trial, called the Medley trial, involved 128 people in Australia who were 65 years old and older. The participants were randomly assigned to eat either the MedDiet or follow their normal diet for six months.
Blood samples from the two groups were compared. A variety of biomarkers of the MedDiet, including fatty acids and carotenoids—the pigments that give vegetables like pumpkins, carrots, and tomatoes their color—were found. The biomarkers were combined into an overall score that could predict whether participants were assigned to and following a MedDiet.
“Our research offers a novel approach to combine multiple biomarkers as a measure of following the Mediterranean diet,” Jakub Sobiecki, of the University of Cambridge in the United Kingdom and the first author of the study, said in a news release. “It enabled us to study the link between this dietary pattern and the risk of new-onset type 2 diabetes in a more robust manner than in prior research.”
In the second part of the trial, University of Cambridge researchers analyzed data of 340,234 middle-aged people living in eight European countries who were participants in a long-term European study. The data included blood samples and self-reported diet information.
After about a 10-year follow-up, 9,453 participants developed type 2 diabetes and had relevant biomarkers measured. The researchers then compared biomarker scores from the 9,453 to 12,749 randomly selected participants in the large study who did not have diabetes. The investigators found a nearly 30 percent reduction in diabetes risk using the biomarker data, compared to a 10 percent reduction from the self-reported data.
By using the biomarker score, the investigators identified a stronger link between the MedDiet and reduced risk of type 2 diabetes than when self-reporting was used. This suggests that previous self-report-based studies may have underestimated the impact of the MedDiet.
Dr. Nita Forouhi, senior author of the study, told NBC News that the findings strengthened the case for recommending the MedDiet for the prevention of type 2 diabetes.
“The 20 percent of participants with the highest values of the biomarker score had a 62 percent lower risk of new-onset type 2 diabetes relative to the 20 percent with the lowest biomarker score values,” said Forouhi, who is also a professor of population health and nutrition and program leader in nutritional epidemiology at the University of Cambridge.
For someone consuming an average of 2,000 calories per day, researchers defined the MedDiet as, at least:
• 2 to 3 tablespoons of olive oil.
• Five servings of vegetables (75 grams each).
• Two to three servings of fruits (150 grams each).
• Five servings of cereal products (between 30-120 grams each, depending on the specific product).
And a daily maximum of:
• One medium potato.
• One serving of milk (250 mL).
• Two glasses of red wine (150 mL each).
Weekly recommendations included:
• Six servings of Greek low-fat yogurt (170 grams each).
• One to three servings of poultry (100 grams each).
• At least five servings of nuts (35 grams each).
• At least three servings of legumes (75 grams each).
• At least three servings of fish (150 grams each).
And a maximum of:
• Four servings of cheese (40 grams each).
• One serving of red meat (100 grams).
• Five eggs.
According to Dr. Anna Beth Bradley, an assistant professor of medicine, diabetes, endocrinology, and metabolism at the Vanderbilt University School of Medicine, the findings of the recent study are significant since diabetes rates are growing globally.
“If you look at the prevalence of diabetes globally, you see that in Europe, the incidence is around 6 percent to 7 percent, while in the U.S., it’s around 11 percent, which suggests that the standard American diet probably has contributed to the rise in diabetes,” Bradley told NBC News. “That terrible American diet is leaking over to other countries with diabetes rising in pretty much every country.”
The MedDiet helps to manage diabetes since the eating style is a great source of fiber-rich plant foods and does not include many processed sweets, Frances Largeman-Roth, a registered dietitian nutritionist, told TODAY.com. The diet is “beneficial for blood sugar management and lowering A1C levels, which measures your average blood sugar levels over the last 3 months” Largeman-Roth said.
In addition to following the MedDiet, Largeman-Roth recommends eating a wide variety of fruits and vegetables, getting 25-35 mg of fiber per day, and trying to stay physically active and move every day.
While there were positive aspects to the recent study, the research team noted that additional studies are needed to confirm and extend these new findings since they do not know to what extent the biomarker score is specific for the Mediterranean diet.
Linda Van Horn, a clinical nutrition epidemiologist at the Feinberg School of Medicine, Northwestern University in Chicago, told NBC News that the biomarkers do not determine whether the benefits are from fruit and vegetable consumption or some other aspect of the diet. Still, this approach “is more objective, so I would say it’s a step in the right direction,” she said.