Background: Up to now, the association between vitamin D and cardiorespiratory fitness (CRF) is still inconsistent and there is a lack of a comprehensive review on this topic. Aim: To systematically review the literature including both observational studies and randomized controlled trials (RCTs) on the association between vitamin D and CRF in the general population. Methods: The literature was investigated by exploring databases of PubMed, EMBASE, Scopus and ISI Web of Science as well as a manual search up to April 2017 by using related MeSH terms and key words. All the English-language articles that were conducted in the general population without any restriction on age range of participants and date of publication were included in the study. Results: Among the 731 records which were found initially, a total of 20 articles including 18 cross-sectional studies and 2 RCTs fulfilled the inclusion criteria. Among the cross-sectional studies, findings on the association between serum 25(OH) D and CRF were incongruent. Additionally, studies which had reported significant results varied remarkably in terms of sample size, study population and the effect size of the association. In addition, RCTs found no significant improvement in CRF following vitamin D supplementation. Conclusion: Overall, evidence from cross-sectional studies does not support a strong association between vitamin D and CRF, although a number of studies demonstrated modest positive associations. Furthermore, limited RCTs did not confirm such an association. Further high quality research is needed to obtain a definite conclusion on this topic. ".
Keywords: Vitamin D; cardiorespiratory fitness; physical fitness.