In a study published in November 2020 in JAMA Network Open, researchers found that women who ate a Mediterranean (MED)-style diet, rich in healthy fats, fruits, and vegetables, had a 30 percent lower rate of type 2 diabetes incidence compared with women who did not. The new research included an examination of several mechanisms at work in the body to try to identify differences between the MED-like diet group and the normal diet group that could lead to the reduced risk in developing the disease. In addition to finding the diabetes risk reduction, investigators were able to better understand the potential reasons for those benefits, says a coauthor of the study, Samia Mora, MD, an associate professor at Harvard Medical School and a physician at Brigham and Women’s Hospital in Boston. “The largest contribution came from biomarkers of insulin resistance, followed by biomarkers of adiposity or body mass index (BMI), HDL (high-density lipoprotein) measures, and inflammation,” says Dr. Mora. “I think the message of these findings is that what people eat now matters for their health, even up to a quarter of a century later. Many people tend to underestimate the impact of diet on their health risks,” she says. RELATED: The Prediabetes Diet Everyone Should Follow
Mediterranean Diet Has Proven Benefits for Improving Metabolic Health
People who follow a Mediterranean diet tend to cook with olive oil, which is a heart-healthy fat, and eat plenty of fruits, vegetables, legumes, nuts and seeds, moderate amounts of fish and dairy products, limited amounts of red and processed meats like bacon and hot dogs, and limited foods with added sugar. They also drink some red wine. Several previous studies have reported positive health benefits in people who eat a Mediterranean or MED-like diet. For example, a meta-analysis that included 50 studies and 534,096 people published in the Journal of the American College of Cardiology found that adherence to the Mediterranean diet was associated with a reduced risk for metabolic syndrome. Researchers also found that a MED diet could have a protective effect against developing this group of diseases, which include abdominal obesity, high blood pressure, high cholesterol, and insulin resistance. People with metabolic syndrome are at increased risk of coronary heart disease and type 2 diabetes. RELATED: 8 Scientific Health Benefits of the Mediterranean Diet
A Diet Rich in Fruits, Veggies, and Healthy Fats Linked With Lower Diabetes Incidence
The 25,317 subjects involved in the current research were from the Women’s Health Study, which enrolled female healthcare professionals between 1992 and 1995 and collected data through December 2017. Researchers used data gathered from a food frequency questionnaire and blood samples that were collected at the time of enrollment. The average age of participants was 52.9; about 95 percent of the participants were white, 2.3 percent were Black, and 1.1 percent were Hispanic. Using self-reported data from the questionnaires, researchers assigned each participant a MED diet intake score from 0 to 9; points were given for high intakes of fruits, vegetables, whole grains, legumes, nuts and fish, moderate consumption of alcohol, and for eating less red or processed meat. Blood samples of the participants were measured for markers that included blood pressure, lipids (LDL, HDL, triglycerides), glycemic level, insulin resistance, lipoproteins, and creatinine. Investigators found that during the 20-year-plus follow-up, 2,307 of the participants developed type 2 diabetes. People who followed the principles of the MED diet more closely (indicated by an assigned score of 6 or higher) developed diabetes at a rate that was 30 percent lower than people who didn’t consume a MED-like diet (scores were 3 or less). After assessing 40 different biomarkers that are typically associated with type 2 diabetes, researchers used those measurements along with the MED diet score to calculate the contribution of each of those factors to diabetes. Biomarkers of insulin resistance was the largest contributor, followed by BMI, HDL measures, in particular HDL particle size, and inflammation. Researchers also identified BCAA (branch-chain amino acids), VLDL (a type of cholesterol known as very low density lipoprotein), LDL measures (the way lipids are metabolized, but not actually LDL cholesterol itself), and blood pressure, though they determined these factors contributed relatively less to participants’ type 2 diabetes risk. RELATED: A Complete Mediterranean Diet Food List and 14-Day Meal Plan
Results Help Clarify Why a Mediterranean Diet May Impact Diabetes Risk
This study shows the characteristics for doctors to look at in women in this age group to help them have a specific conversation about a patient’s risk of type 2 diabetes, including what may be the factors behind that risk, and how to slow or delay the diagnosis of the disease, says Kathleen Wyne, MD, PhD, a professor of medicine in the division of endocrinology, diabetes, and metabolism at the Ohio State University Wexner Medical Center in Columbus. Dr. Wyne was not involved in the current research. “It also gives us specific parameters to measure and follow in this population, which is much more interesting than just telling people to exercise and lose weight,” she adds. The study authors acknowledge that the lack of diversity in participants is a limitation of the study. “Study participants were well-educated female health professionals across the United States who were predominantly white individuals and might have different behaviors than men, individuals from other racial/ethnic backgrounds, or the general public,” they wrote. These results do suggest that the Mediterranean diet is a marker for healthy eating and, possibly, a healthy lifestyle, says Wyne. “The reduced risk may be because the Mediterranean diet replaces unhealthy foods with foods that do not promote inflammation or insulin resistance, and that possibly improve insulin resistance and beta-cell function,” adds Wyne. The primary function of beta cells is to produce and secrete insulin, the hormone that regulates blood glucose levels. RELATED: A Comprehensive Guide to an Anti-Inflammatory Diet
Diet Shows Strong Benefit for Women With Overweight or Obesity
When researchers further broke down their findings, they found an association between the Mediterranean diet and lower diabetes risk only in women who had a BMI of 25 or higher, the authors write. A BMI of 25 or higher signals overweight or obesity, notes the Centers for Disease Control and Prevention. “It is important to note that in the population overall there was a benefit of the lower risk for type 2 diabetes. I don’t want people to think that if they’re at normal weight that they are protected from developing diabetes,” says Mora. Although it is possible to have insulin resistance without excess fat, it’s not typical, says Mora. Because type 2 diabetes is basically driven by excess fat in the wrong places in our bodies and by a state of metabolic dysregulation, it makes sense that women with a BMI of 25 or higher would especially benefit from being on a Mediterranean-style diet compared with their counterparts, she says. If women made it to midlife and are still a healthy weight, then they probably have good habits and will continue them, Wyne says. “The participants who are overweight clearly stave off the diabetes with the healthy choices of the MED diet; even if they do not fully prevent it, they clearly prolong the time until type 2 diabetes emerges,” wrote Wyne. RELATED: Study Suggests How a Plant-Based Diet Helps Prevent Type 2 Diabetes
Adopting Even a Few Elements of a Mediterranean Diet May Help Fend Off Diabetes
Unlike some other diets, a Mediterranean diet is relatively simple to follow and can be easier to stick with over the long term than more restrictive eating plans, says Mora. “It is a flavorful diet with a lot of variety,” she says. Based on these findings, Wyne suggests incorporating at least a few of the elements of a Mediterranean diet onto your plate. “One of the keys is to replace current less-healthy foods you may be eating with the healthy ones that are counted in this scoring system,” says Wyne. Even changes that seem small can make a difference, says Mora. “In our study, just a few points on the scale was enough to be associated with the reduced risk for type 2 diabetes,” she says.
