Can vegetables intake pattern mediate the relationship between fast-food and cognitive performance in adolescents? The Cogni-Action project

Vegetables play a crucial role in mitigating metabolic disorders. However, no studies have investigated the potential mediating role of vegetable intake in the inverse association between fast-food intake and cognitive performance in adolescents. Furthermore, sex differences in this mediation pathway remain unclear. This cross-sectional study included 1296 Chilean adolescents (50% girls; 10–14 years old). Cognitive functioning was assessed using eight cognitive tasks, from which a Global Cognitive Performance (GCP) score and four cognitive domains were derived: cognitive flexibility (CF), inhibitory control (IC), working memory (WM), and fluid reasoning (FR), using principal component analysis. Vegetable and fast-food intake were evaluated using the Mediterranean Diet Quality Index questionnaire. Mediation analyses were conducted using a Generalized Linear Model with 5000 bootstrapped samples. Fast-food consumption was inversely associated with cognitive performance ( r = -0.140; p < .001). Considering full sample, vegetable mediated this relationship for GCP (β = -0.29; 95%CI -0.42, -0.18), CF (β = -0.20; 95%CI -0.32, -0.08), WM (β = -0.18; 95%CI -0.32, -0.06), and FR (β = -0.12; 95%CI -0.24, -0.00). No significant mediation was found for IC ( p = .228). In boys, mediation was observed for GCP (β = -0.29; 95%CI -0.49, -0.12) and WM (β = -0.23; 95%CI -0.46, -0.04), while no significant mediation was found for CF, IC, or FR. For girls, mediation was found for GCP (β = -0.28; 95%CI -0.46, -0.13) and CF (β = -0.21; 95%CI -0.39, -0.06), whereas no significant mediation was found for IC, WM, and FR. These findings suggest that consuming at least two servings of vegetables per day may play a mediating role in the inverse association between fast-food consumption and cognitive performance, highlighting sex differences across cognitive domains.