Association between protein intake and physical fitness in adolescence.

INTRODUCTION: This study aimed to determine whether protein sources are differentially associated with physical fitness (PF) components. METHODS: The study participants were 796 adolescent boys and 881 girls (age range, 12.5-17.5 years) participating in the HELENA study. Standardized PF procedures included upper body muscular strength, cardiorespiratory fitness (CRF), flexibility, and lower body explosive strength. Proteins sources were assessed using 3 days of dietary recalls and data were analyzed using a linear mixed regression model. RESULTS: For both boys and girls, only CRF was associated with plant-protein intake in the unadjusted and adjusted models. No association was found between PF components and animal protein intake. The association between total protein intake and CRF was only significant in boys. CONCLUSION: The present study findings indicate that plant protein intake is positively associated with CRF, thereby supporting the recommendation to move toward a more plant-based diet to reduce the well-described longitudinal decline in CRF with age.