Systematic evaluation and meta-analysis of the effects of major dietary patterns on cognitive function in healthy adults.

Purpose: Evidence shows diet promotes brain health. Combining foods and nutrients may have beneficial synergistic effects, but the effects on cognitive function interventions are inconsistent. So, a meta-analysis of RCTs was conducted to examine the specific effects on cognitive function.

Methods: We searched four databases from creation to April 2023. Eligible randomized controlled trials were identified. A random-effects meta-analysis was used to combine standardized mean differences (SMD) (95% confidence intervals [CI]), and homogeneity tests for a variance were calculated.

Results: A total of 19 studies involving 12,119 participants were included in this systematic review. The dietary intervention group had a positive effect on overall cognitive functioning compared to the control group (SMD = 0.14, 95% CI [0.08, 0.20], P < 0.00001). The dietary intervention improved executive function, processing speed and language skills (SMD = -0.10, 95% CI [-0.17,-0.04], P = 0.002, I² = 0%), (SMD = -0.16, 95% CI [-0.23,-0.09], P < 0.00001, I² = 0%), (SMD = 0.10, 95% CI [0.01, 0.20], P = 0.03, I² = 0%). The dietary intervention had no effect on delayed memory and spatial ability (SMD = 0.04, 95% CI [-0.02, 0.09], P = 0.20, I² = 0%), (SMD = 0.08, 95% CI [-0.01, 0.16], P = 0.08, I² = 0%).

Conclusion: The Mediterranean diet, a diet with restricted caloric intake, a diet incorporating aerobic exercise, a low-carbohydrate diet, and a healthy lifestyle diet (increased intake of fruits and vegetables, and weight and blood pressure management) appear to have positive effects on cognitively healthy adults, as reflected in their overall cognitive, processing speed, executive, and language functions.

Prospero registration number: CRD42023414704.