Mediterranean Diet Linked to 30% Lower Diabetes Risk in Women

Samira Mora, MD

A new study from a team at Brigham and Women’s Hospital and Harvard Medical School details the benefit of adhering to a Mediterranean diet for preventing diabetes in women.

Results of the study, which assessed impact of dietary choices in a cohort of 25,000 women over 20 years, indicate greater adherence to a Mediterranean diet was associated with a 30% lower risk of type 2 diabetes.

"Our findings support the idea that by improving their diet, people can improve their future risk of type 2 diabetes, particularly if they are overweight or have obesity," said study investigator Samia Mora, MD, MHS, of the Brigham's divisions of Preventive Medicine and Cardiovascular Medicine and an associate professor at Harvard Medical School, in a statement. "A lot of the benefit we see can be explained through just a few pathways. And it's important to note that many of these changes don't happen right away -- while metabolism can change over a short period of time, our study indicates that there are longer term changes happening that may provide protection over decades."

With an interest in closing the knowledge gap related to diabetes onset and nutrition, investigators designed their study as an analysis of data from the Women’s Health Study. From the study, which included 28,345 women who voluntarily provided blood samples, investigators identified 25,317 women for inclusion in their study.

All patients included in the current study were free of diabetes and had completed validated semiquantitative food-frequency questionnaires, which assessed intake of 131 food items, at baseline. The mean age of the study population was 52.9 (9.9) years and they had a mean follow-up time of 198 (5.8)years.

For the purpose of the analysis, Mediterranean intake scores ranging from 0-9 were calculated for each patient. The primary endpoint of the study was incident cases of type 2 diabetes. Investigators also hoped to assess what proportion of risk reduction was explained by risk factors and biomarker changes.

Upon analysis, investigators found scores of 6 or more were associated with as much as a 30% lower risk of developing type 2 diabetes (age-adjusted and energy-adjusted HR, 0.70; 95% CI, 0.62-0.79; when regression models were additionally adjusted with BMI: HR, 0.85; 95% CI, 0.76-0.96) compared to those with scores of 3 or less. Further analysis indicated biomarkers of insulin resistance were responsible for the largest proportion of risk reduction (65.5%), followed by BMI (55.5%), high-density lipoprotein measures (53.0%), and inflammation (52.5%). Results suggested smaller contributions were linked to changes in branched-chain amino acids (34.5%), very low-density lipoprotein measures (32.0%), low-density lipoprotein measures (31.0%), blood pressure (29.0%), and apolipoproteins (23.5%)—changes in HbA1c accounted for less than 2% of the risk reduction.

In posthoc analyses, investigators found the inverse associations of adherence to a Mediterranean diet and type 2 diabetes was only present in women with a BMI of 25 or greater at baseline (age- and energy-adjusted HR, 1.01; 95% CI, 0.77-1.33; P for trend =.92).

"Most of this reduced risk associated with the Mediterranean diet and type 2 diabetes was explained through the biomarkers related to insulin resistance, adiposity, lipoprotein metabolism and inflammation," said study investigator Shafqat Ahmad, PhD, a researcher in the Molecular Epidemiology Unit at Uppsala University, Sweden, in the aforementioned statement. "This understanding may have important downstream consequences for the primary prevention of diabetes disease."

This study, “Association of the Mediterranean Diet With Onset of Diabetes in the Women’s Health Study,” was published in JAMA Network Open.