Cardiorespiratory Fitness in Low Calcium Consumers: Potential Impact of Calcium Intake on Cardiorespiratory Fitness

<b>Background:</b> Calcium is essential for maintaining bone health, facilitating muscle contractions, regulating body temperature, and supporting aerobic metabolism. While the relationship between physical activity and calcium metabolism is well established, the impact of calcium intake on cardiorespiratory fitness (CRF) remains underexplored. The main aim of this study was to assess the effects of calcium intake on CRF and the mediation effect of calcium intake on the relationship between vigorous physical activity participation and CRF. <b>Methods:</b> Analyses were performed on a sample of 576 adult participants (257 males and 319 females) from the Quebec Family Study (QFS) for whom data were available for calcium intake, CRF, and body composition. The effects of calcium intake on CRF and body composition were analyzed by comparing subjects classified into sex-specific tertiles of calcium intake using general linear mixed models. Pearson correlations were also used to document the associations between calcium intake, CRF, and body composition. A mediation analysis was used to determine the effect of calcium intake as a mediator of the association between vigorous physical activity and CRF. <b>Results:</b> The comparison of calcium-based tertiles revealed that low calcium consumers had lower CRF, especially in males. In both males and females, correlation analysis showed that calcium intake was positively associated (<i>p</i> < 0.05) with CRF. Mediation analyses revealed that calcium intake explains an insignificant fraction of the physical activity-CRF relationship. Between-tertile comparisons showed reduced body fat and increased fat-free mass levels when increasing calcium intake, although some of these effects were not statistically significant. <b>Conclusions:</b> The results of this study suggest that low calcium intake is associated with reduced aerobic capacity in adult males and females. While the positive relationship observed between calcium and aerobic fitness aligns with calcium's known physiological roles, further research is needed to clarify the exact mechanisms by which this micronutrient may influence aerobic capacity.