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Mediterranean diet tied to improved cognition in type 2 diabetes



People with type 2 diabetes whose diet followed a “Mediterranean” pattern – high in vegetables, legumes, fish, and unsaturated fats – saw global cognitive improvements over a 2-year period, compared with individuals with different eating patterns, even if the latter incorporated healthy dietary features. In addition, effective glycemic control seemed to have a role in sustaining the benefits associated with the Mediterranean-type diet.

Adults without type 2 diabetes, meanwhile, did not see the cognitive improvements associated with a Mediterranean diet, suggesting that the pathways linking diet to cognition may be different for individuals with and without diabetes, according to Josiemer Mattei, PhD, of the Harvard T.H. Chan School of Public Health in Boston and colleagues.

The investigators used data from the Boston Puerto Rican Health Study, a longitudinal cohort of about 1,499 adults aged 45-75 years who lived in Boston and identified as Puerto Rican, for their research, which was published in Diabetes Care.

At baseline, participants were administered a questionnaire to capture their eating patterns. Four diet-quality scores – Mediterranean Diet Score, Healthy Eating Index, Alternate Healthy Eating Index, and DASH (Dietary Approaches to Stop Hypertension) were analyzed. The participants were also screened for diabetes, and nearly 40% of them were found to have type 2 diabetes at baseline (74% uncontrolled). They underwent a battery of cognitive tests, including the Mini-Mental State Exam and tests for verbal fluency, executive function, word recognition, and figure copying. The study endpoints included 2-year change in global cognitive function as well as executive and memory function. At 2 years, data was available for 913 participants.

Among participants with type 2 diabetes, greater adherence to a Mediterranean-style diet was significantly associated with a higher positive change at the 2-year follow-up in global cognitive function score (0.027 [SD, 0.011]; P = .016), the Mini-Mental State Exam, and other individual tests. The association was significant for those who were under glycemic control at baseline and who remained stable or improved over 2 years, but not for those with poor or worsening glycemic control.

“The Mediterranean diet explained as much or more of the variability in predicting changes in cognitive function in our study as did age, especially for participants with type 2 diabetes under glycemic control. ... This dietary pattern may provide more cognitive benefits [in this patient group] than other modifiable and nonmodifiable factors,” the authors wrote in their analysis. They stressed that a Mediterranean dietary pattern can be realized through foods and dishes that are already standard in many Puerto Rican households.

In participants who did not have diabetes, improvement in memory function measures was seen in association with a Mediterranean diet, but also with adherence to other eating patterns that are deemed healthy. That suggests that for this subgroup, any evidence-based healthy diet – not just the Mediterranean diet – may have some benefits for memory function.

“Dietary recommendations for cognitive health may need to be tailored for individuals with versus without type 2 diabetes,” the authors concluded.

Dr. Mattei and colleagues acknowledged as a limitation of their study its observational design.

The study received funding from the National Heart, Lung, and Blood Institute; the National Institute on Aging; and Harvard University. The authors reported no financial conflicts of interest.

SOURCE: Mattei et al. Diabetes Care. 2019;42(8):1372-9.

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