In a recent study published in Preventive medicine reports Journal, researchers conducted a randomized clinical trial (RCT) to test whether adhering to the Mediterranean diet (MedDiet) with or without calorie restriction could improve cognition.
Study: Effect of Mediterranean diet and Mediterranean diet plus calorie restriction on cognition, lifestyle, and cardiometabolic health: A randomized clinical trial. Image Credit: ElenaEryomenko/Shutterstock.com
Obesity, lifestyle choices including diet and exercise, and cardiometabolic comorbidities increase the risk of cognitive decline. To date, no effective pharmaceutical therapies are available to prevent, delay or manage cognitive deficits.
However, studies have shown that the MedDiet and weight loss benefit cognition, and the combination of the two can improve cognitive function. However, RCTs have shown inconsistent results, with nutrition having a favorable or negligible impact on cognition, warranting further research.
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In the present three-arm RCT, researchers evaluated the potential cognitive benefit of adhering to the MedDiet with or without calorie restriction.
The Building Research in Diet and Cognition study was conducted between January 2017 and October 2020, involving 185 Chicago residents, ages 55 to 85, mostly female (86.0%), with obesity. Participants were randomly assigned to the MedDiet calorie restriction intervention group (n=72, 25.0% kcal restriction for 5.0 to 7.0% weight loss), MedDiet alone group (n =72) or the control group (n=36).
The dietary interventions period was eight months, including 26 sessions for the intervention groups and 25 sessions for the control group, and follow-up assessments were performed for 14.0 months.
The primary outcome of the study was a change in cognitive assessment scores for attention, information, and processing (AIP); learning, memory and recognition (LMR); and executive function (EF).
Secondary outcomes of the study were changes in body weight, cardiometabolic biomarkers, and lifestyle. The team estimated habitual dietary intake using the Harvard Food Frequency Questionnaires (HFFQS), and physical activity was estimated using a triaxial accelerometer worn on the nondominant wrist for ≥4.0 days and ≥10.0 hours per day .
To assess cardiometabolic risk, blood pressure, serological levels of low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), total cholesterol, triglycerides (TG), insulin, glycated hemoglobin (HbA1c ), high-sensitivity C-reactive protein (hs-CRP), and glucose levels were measured in blood samples provided by the patients.
Individuals were recruited through introductions to senior living facilities and advertisements in local neighborhoods, and underwent telephone and physical screening prior to enrollment.
Individuals with a Body Mass Index (BMI) between 30.0 and 50.0 kg/m2Mediterranean diet adherence screener score ≤6.0, Montreal Cognitive Assessment (MoCA) scores ≥19.0, and those who could speak English were included in the analysis.
The team excluded people who could not exercise according to EASY physical activity screening, HbA1c serologic values >9.0 at screening, and significant comorbidities such as autoimmune disorders or severe cardiovascular, lung, kidney, and liver disease.
In addition, people who used warfarin, suffered from serious psychiatric conditions, people with a history of bariatric surgery, people concurrently involved in formal weight reduction programs, and those who had participated in weight training activities were excluded from the analysis. research associated with cognition in the previous 12 months. . Individuals adhering to the MedDiet received one ounce of almonds and three tablespoons of extra virgin olive oil per day.
Theories of social determination and social cognition have been used to guide adherence to study interventions. In addition, participants underwent hands-on training (meal preparation) and didactic dietetics. All individuals were advised to achieve moderate-to-vigorous physical activity levels at 150.0 minutes per week. Participants in the control group received weekly general health newsletters.
Dietary interventions had no significant impact on LMR, EF, AIP, or MoCA scores. The mean increase in scores for MedDiet adherence plus calorie restriction and MedDiet alone interventions were 6.30 points and 4.80 points, respectively, compared with the control group (+0.60 points).
The mean weight reductions among individuals in the MedDiet plus calorie restriction group, MedDiet alone group, and control group were 4.60 kg, 2.60 kg, and 0.60 kg, respectively.
Dietary interventions showed no significant influence on exercise and cardiometabolic biomarker levels, although participants in the MedDiet plus calorie-restricted group had lower fasting insulin levels and lower body weight values than in the other groups.
In particular, a significant decrease in visceral adiposity was observed; however, total body fat percentage did not differ significantly between groups after the intervention. Both participants in the intervention group had similar frequency for group sessions, and 67.0% of study participants were hypertensive.
The study results showed that adherence to the MedDiet with or without calorie restriction did not have a significant influence on cognition. However, MedDiet interventions significantly reduced central obesity and body weight and improved diet quality.
The cognitive benefit of adhering to the MedDiet with or without restricting caloric intake could be associated with the prevention or delay of pathological cognitive aging instead of the maintenance of normal cognitive aging.
Alternatively, the strength of the effect could have been reduced due to the use of several cognitive assessment scores instead of a composite score. Furthermore, the limited sample size and short duration of the interventions may have reduced the impact of dietary interventions.
Further research needs to be conducted using objective dietary assessments, larger sample sizes, and longer intervention durations to account for the nutrient intake impairment of processed foods in the MedDiet.