Following a Mediterranean diet may improve cognitive function in people living with diabetes, according to a US study that tracked almost 1000 diets over a two-year period.
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The Mediterranean diet incorporates foods traditionally eaten in countries bordering Mediterranean Sea, including France, Greece, Italy, and Spain, but the exact contents of the diets traditionally followed in these countries may vary.
Overall, Mediterranean diets are high in fruits, vegetables, legumes, nuts, beans, cereals, grains, and fish. Unsaturated fats such as olive oil are also very common in Mediterranean diets. They are also low in red and processed meat. As such, Mediterranean diets have been associated with better cognitive and cardiac health.
Lead author of the study Josiemer Mattei from the Harvard T.H Chan School of Public Health in Boston explained the positive effects of this particular diet on the brain:
A healthy Mediterranean diet includes foods that are rich in fruit and vegetables, which [have] antioxidants, and in fish and oils, which include healthy fats. These nutrients help sustain cognitive function by reducing inflammation and oxidation in the brain.”
The study, which was published in the journal Diabetes Care, aimed to discover “associations of a Mediterranean diet score (MeDS) with a 2-year change in cognitive function by type 2 diabetes and glycemic control status.” The Mediterranean diet scores would then be compared to other diet quality scores.
Data from the longitudinal Boston Puerto Rican Health Study was used to inform the study, and researchers tracked and assessed the eating habits of 913 participants of the Health Study. The participants were tested for type 2 diabetes and took tests on cognitive function, memory function, and executive function.
To assess how closely the participants were following the Mediterranean diets, the researchers scored the amount of the main ingredients of the Mediterranean diet they ate over the two years. Scores were also taken according to how much food they ate that made up two other diets that improve heart health, including the Dietary Approaches to Stop Hypertension (DASH) diet.
Mediterranean diet supports 'optimal cognitive function'
Improvements in memory function were seen in people without diabetes who were following a Mediterranean diet, but other cognitive functions were not seen to improve significantly. In fact, other diets that improved heart health resulted in a more marked improvement in cognitive function in those without diabetes.
However, the Mediterranean diet significantly improved cognitive function in people with diabetes. Word recognition and clock drawing skills were seen to improve more when compared with people who did not follow a Mediterranean diet.
The cognitive benefits brought on by the Mediterranean diet were only seen in people that had well-controlled blood sugar levels, and benefits were not as clear in those who began the study with poorly controlled blood sugar levels or those whose blood sugar control deteriorated during the course of the study.
Mattei explained that the whole grains and legumes may be the element in a Mediterranean diet that helps to control blood sugar levels as well as contributing to better overall cognitive function. The study drew the conclusion that “adhering to a Mediterranean diet and effectively managing type 2 diabetes may support optimal cognitive function.”
Increase nutrient intake and lower dietary sugar
The researchers also state that a healthy diet in general can help to improve cognitive function, especially memory function, in people with type 2 diabetes, suggesting that it is not only the Mediterranean diet that can bring on these positive cognitive improvements.
The study only included Puerto Rican participants, meaning its findings may not extend to people from other racial and ethnic backgrounds, or people who do not follow Mediterranean diets. A second limitation of the study is that data on the participants’ dietary intake was self-reported, which is vulnerable to bias and inaccuracy.
Despite this, Allen Taylor from the Tufts University USDA Human Nutrition Research Center on Aging in Boston, who was not involved in the study, said:
There are many salutary affects of consuming a Mediterranean diet that is rich in fruits and vegetables, lower in simple sugars, lower in red and processed meats, with a few servings per week of fish.”
Mattei, J., et al. (2019). The Mediterranean Diet and 2-Year Change in Cognitive Function by Status of Type 2 Diabetes and Glycemic Control. Diabetes Care. doi.org/10.2337/dc19-0130.