Title : Iron and vitamin status biomarkers and its association with physical fitness in 2 adolescents

60 There is a lack of studies that analyse the association between micronutrient-related 61 biomarker status and physical fitness in adolescents. In the present study, biochemical 62 parameters for iron and vitamin status were studied along with objective measures of 63 physical fitness in healthy male and female European adolescents. 1089 adolescents (580 64 girls, 12.5-17.5 years) from the HELENA cross-sectional study were included. Hierarchical 65 linear models were performed to determine the associations between micronutrient 66 biomarkers and physical fitness. Age, seasonality, latitude, body mass index, menarche (in 67 girls) and physical activity were used as covariates. For cardiorespiratory fitness, 68 concentrations of hemoglobin, retinol and vitamin C in male adolescents and, β-carotene and 69 25(OH)D in female adolescents were associated with VO2max. For muscular fitness, 70 concentrations of hemoglobin, β-carotene, retinol and α-tocopherol in male adolescents and 71 β-carotene and 25(OH)D in female adolescents were associated with better performance of 72 the standing long jump test. In summary, concentrations of hemoglobin and most antioxidant 73 vitamins in male adolescents and β-carotene and 25(OH)D in female adolescents were 74 positively associated with cardiorespiratory and muscular fitness, after controlling for 75 relevant confounders. The associations between physical fitness and iron or vitamin status 76 observed in this cross-sectional study in adolescents should be followed up by a study 77 specifically designed to evaluate causal relationships. 78 79