Researchers uncover biomarkers linking Mediterranean diet to reduced diabetes risk, call on policymakers for change

20 Nov 2020 --- Researchers at the Brigham and Women’s Hospital have uncovered biomarkers explaining the longstanding link between Mediterranean diets and lowered risk of Type 2 diabetes (T2D). Leaders of the study are calling on policymakers and industry to enact urgent changes in light of the findings.

In a study of more than 25,000 women spanning 25 years, the investigators found a Mediterranean-like diet reduced T2D risk by 30 percent and discovered several key responsible biological mechanisms. The findings are published in JAMA Network Open. 

“The Mediterranean diet has been associated with a lower risk of T2D risk, but the precise mechanisms through which Mediterranean diet intake may reduce the long-term risk of T2D are not well understood,” Dr. Shafqat Ahmad, a researcher on the project, tells NutritionInsight. 

“We aimed to investigate the biological mechanisms that may mediate this cardiometabolic benefit.”

“Biomarkers of insulin resistance made the largest contribution followed by adiposity, HDL measures (cholesterol), and inflammation, with lesser contributions from branched-chain amino acids, blood pressure, and apolipoproteins.”

The findings provide original insight into the biology linking T2D and diet, and the researchers emphasize the importance of understanding these mechanisms for preventive medicine. 

The Mediterranean diet is rich in plants (nuts, seeds, fruits, vegetables, whole grains, legumes) and olive oil. It includes a moderate intake of fish, poultry, dairy, eggs, alcohol, and rare use of meats and sweets. 

Insulin resistance was found to be the greatest contributor to T2D risk. Examining female health professionals
Investigators examined the Women’s Health Study outcomes, a longitudinal cohort study of female health professionals. 

It was originally designed to evaluate the effects of vitamin E and low-dose aspirin on heart disease and cancer risk. 

Additionally, participants were asked to provide blood samples and complete food frequency questionnaires (FFQs) about dietary intake when the study began. They also answered other questions about lifestyle, medical history and demographics. 

Researchers reevaluated the data to examine how and why Mediterranean diets have an impact on T2D risk.

To do so, they assigned each participant a Mediterranean diet intake score from 0 to 9. They examined a range of 40 biomarkers representing different cardiometabolic pathways and clinical factors, which could explain the connection between the Mediterranean diet and T2D. 

“We found that women who were in the top quartile of baseline consumption of Mediterranean diet intake had up to 30 percent lower risk of T2D, which in large can be explained by both traditionally measured and novel biomarkers,” explains Ahmad. 

Urgent implications for policy and industry 
The results have wide-ranging and urgent implications for both policymakers and nutrition industry players, Samia Mora, an associate professor of medicine at Harvard Medical School, tells NutritionInsight.

“The nutrition industry should promote the healthy dietary attributes of the Mediterranean diet and discourage the unhealthy eating habits brought by worldwide acculturation.”

“They should create opportunities for teaching and adaptation of the Mediterranean diet to different cultures and countries where people may be less familiar with the Mediterranean diet.”

She also argues that policymakers should promote increased awareness among the general public about the health benefits of the Mediterranean dietary pattern. 

“Modest changes in cardiometabolic risk factors account for a large proportion of the Mediterranean diet’s effects on reducing the risk of T2D. They may have important downstream consequences for primary prevention of other chronic diseases including cardiovascular diseases and cancer,” Mora asserts. 

Further research needed
Despite the study’s length and depth, Mora acknowledges the need for future investigations to further the findings, saying that widening the pool of participants could produce more generalizable results. 

“Study participants were well-educated female health professionals across the US who were predominantly white and might have different behaviors than men, individuals from other racial/ethnic backgrounds, or the general public.”

“Dietary information was assessed through self-reported FFQs, which might lead to the possibility of exposure misclassification, underreporting and overreporting. Therefore, the benefit for lower risk of T2D may be even greater than 30 percent.” 

By Louis Gore-Langton