Single-Nucleotide Polymorphisms (SNPs) in Vitamin D Physiology Genes May Modulate Serum 25(OH)D Levels in Well-Trained CrossFit® Athletes, Which May Be Associated with Performance Outcomes.

Vitamin D is a key micronutrient in the function of the skeletomuscular system. Athletes are at increased risk of developing vitamin D deficiency during the execution of very demanding disciplines such as CrossFit®. Single-nucleotide polymorphisms (SNPs) may influence circulating 25-hydroxy-vitamin D (25(OH)D) levels. An observational, longitudinal pilot study was conducted with 50 trained males according to specific inclusion criteria. Blood samples were obtained to determine 25(OH)D, vitamin D-binding protein (VDBP), vitamin D-receptor (VDR)circulating levels, and the presence of SNPs after DNA isolation and genotyping: rs10741657 to CYP2R1, rs2282679 to GC and rs2228570 to VDR genes. Significant differences (p < 0.05) in 25(OH)D concentration were determined between the biallelic combinations of rs228679 (GC) and rs228570 (VDR). The VDBP and VDR proteins did not show different levels in the case of the rs10741657 (CYP2R1) alleles. Statistically significant weak positive correlations (p < 0.05) were observed between 25(OH)D and AA-alleles of the CYP2R1 and VDR genes, and TT-alleles of the GC gene. Additionally, AA (rs10741657 and rs2228570) and TT (rs2282679) have a probability between 2 and 4 of having major effects on the concentration of 25(OH)D. Conversely, GG alleles present a probability of suboptimal values of 25(OH)D of 69%, 34%, and 24% for VDR, GC, and CYP2R1, respectively, showing a strong moderate positive correlation (r = 0.41) between the degrees of sports performance and 25(OH)D plasma levels. CYP2R1 (rs10741657), GC (rs2282679), and VDR (rs2228570) affect the concentration of serum 25(OH)D, as an indicator of vitamin D status and play a critical role in the sports performance of CrossFit® practitioners.