July 1, 2020

The Mediterranean Diet Decreases Diabetes Incidence, Even in the U.S. Population

Results from a large observational study
People with the highest adherence to the Mediterranean diet showed a 17% decrease in incidence of diabetes mellitus compared to those with the lowest adherence. Nuts, legumes, moderate alcohol, and less red and processed meat may be the key.


O’Connor LE, Hu EA, Steffen LM, Selvin E, Rebholz CM. Adherence to a Mediterranean-style eating pattern and risk of diabetes in a U.S. prospective cohort study. Nutr Diabetes. 2020;10:8.

Study Objective

The objective of this study was to assess whether a Mediterranean-style eating pattern would be associated with diabetes risk in a large, nationally representative U.S. cohort of Black and white men and women.


Observational study utilizing the Alternate Mediterranean Diet (aMed) scores to assess level of adherence to a Mediterranean diet while tracking new diagnosis of diabetes. The researchers followed the participants over a median of 22 years. They used Cox regression models to characterize associations of aMed with incident diabetes adjusted for energy intake, age, sex, race and study center, and education for all participants and then stratified by race and body mass index (BMI).


The study included participants from the Atherosclerosis Risk in Communities study prospective cohort without diabetes, cardiovascular disease, or cancer at baseline (N=11,991; mean age 54 years, 56% female, and 75% white). Participants were chosen from 4 U.S. communities.

Study Parameters Assessed

Adherence to the Mediterranean diet as assessed using the validated aMed score and incidence of diabetes.

Primary Outcome Measures

Over a median follow-up of 22 years, there were 4,024 incident cases of diabetes.

Key Findings

Higher aMed scores were associated with lower diabetes risk (0.83 [0.73–0.94] for Q5 vs Q1 [P<0.001], and 0.96 [0.95–0.98] for 1 point higher). Associations were stronger for Black vs white participants (0.74 vs 0.87 for Q5 vs Q1, and 0.95 vs 0.97 for 1 point higher; interaction P<0.001); and weaker for obese vs normal BMI (0.88 vs 0.80 for Q5 vs Q1, and 0.98 vs 0.94 for 1 point higher; interaction P<0.01).

Practice Implications

The Mediterranean diet (Med diet) is rich in fruits, vegetables, whole grains, legumes, nuts, fish, and extra virgin olive oil (EVOO). It has been shown to be an effective eating pattern for decreasing many chronic diseases including diabetes mellitus (DM),1 coronary artery disease,2 neurodegenerative disease,3 and cancer.4 Many of the large-scale studies performed on the Med diet have utilized Mediterranean populations, thereby raising the question of whether this dietary pattern would have the same beneficial results in a U.S. population. Genetics and lifestyle are known factors affecting clinical outcomes. The Mediterranean lifestyle tends to focus more heavily on family and social networks, physical activity, protected sleep patterns, and other arguably pleasurable activities such as enjoyment of meals together, evening strolls, and regular vacations. The effects of the Mediterranean lifestyle have yet to be adequately studied, making it difficult to predict its contribution to Med diet study results.

The Med diet may be of particular importance to the Black community as the study’s researchers found an additional benefit from the Med diet in this population.

This well-designed, large observational study is based on 4 U.S. populations (Washington County, Maryland; suburban Minneapolis, Minnesota; Jackson, Mississippi; and Forsyth County, North Carolina) and aims to clarify the effects of the Med diet on DM specifically in the U.S. population. It found a significant decrease in incidence of DM in those with highest adherence to the Med diet (17% decrease) compared to the lowest adherence. There was also a 4% decrease in DM incidence with each 1-point increment in Med diet adherence, suggesting that the better the adherence, the better the benefit. Higher nut and legume intake, moderate alcohol intake, and lower red and processed meat intake had the strongest associations with noted benefits. While previous studies have also shown benefit of the Med diet specifically in the U.S. population,5,6 this study’s larger sample size and inclusion of 4 distinct U.S. populations and both men and women, as well as Black and white populations, give us a clearer indication of the Med diet’s benefit.

The Med diet may be of particular importance to the Black community as the study’s researchers found an additional benefit from the Med diet in this population. This study subset showed a 26% decrease (vs 17% in all groups) in DM incidence in those with highest vs lowest adherence to the Med diet and a 5% decrease (vs 4% in all groups) in DM incidence with each 1-point increment in Med diet adherence. Given the especially high risk of DM in the Black population,7 this information is particularly relevant as we look for tools for prevention of DM.

The obese population studied showed less benefit from adherence to the Med diet. While the researchers noted some benefit (12% decrease in the obese subset vs 17% for all groups for highest vs lowest adherence; 2% decrease vs 4% for all groups for each 1-point increment), statistical significance was not reached. Reaching and maintaining optimal weight is a fundamental goal in the prevention and treatment of DM. While research exists showing that the Med diet is an effective tool in weight loss,8 taking a personalized approach to obtain ideal weight (which may or may not include the Med diet) would be appropriate prior to implementing the Med diet for decreasing DM incidence in the obese population.

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