The association between the frequency of soy protein intake and lower-limb muscle strength: a multicenter cross-sectional survey of adolescents in Mainland China
Abstract
Background Lower-limb muscle strength is a critical component of physical fitness in adolescents, yet the relationship between dietary protein sources and muscle function in this population remains underexplored. Soy protein, as a high-quality plant-based protein, may support musculoskeletal health, but evidence in Chinese adolescents remains limited. Methods This multicenter cross-sectional survey included 24,602 adolescents (12,755 boys and 11,847 girls) from Mainland China. Frequency of soy protein intake was assessed by weekly consumption frequency and categorized into <2 times/week, 2–4 times/week, and >4 times/week. Lower-limb muscle strength was measured using standing long jump performance. Linear regression and logistic regression models were applied to examine the associations, with adjustments for age, BMI, screen time, breakfast frequency, and physical activity duration. Results Participants with higher soy protein intake demonstrated better performance in the standing long jump across all groups. In the fully adjusted model, compared with the >4 times/week group, boys in the 2–4 times/week and <2 times/week groups showed reductions of −3.266 cm and −6.592 cm in jump distance, respectively; girls showed corresponding reductions of −4.717 cm and −5.992 cm; all P for trend <0.001. Logistic regression confirmed that lower soy protein intake was significantly associated with increased risk of failing the standing long jump standard, with the strongest association observed in girls consuming <2 times/week (OR = 1.79, 95% CI: 1.48–2.17). Conclusion In this cross-sectional survey, increase the frequency of soy protein intake was positively associated with greater lower-limb muscle strength among Chinese adolescents. However, given the observational design, these findings do not establish causality. Further prospective studies are needed to confirm the temporal relationship and underlying mechanisms.