As the relationship between vitamin D and various diseases or health conditions has become known, interest in the contribution of vitamin D to overall health-related quality of life (QoL) has increased. We examined the relationship between vitamin D status and QoL in 273 participants aged 65 years and older. Serum levels of total calcium, phosphorus, intact parathyroid hormone, albumin, and 25-hydroxyvitaminD3 were analyzed. We also recruited data for QoL, physical activity, nutritional impairment, and muscular strength. Ninety percent of the subjects were classified as vitamin D deficient or insufficient. Participants with higher serum 25(OH)D3, calcium, phosphorous, and Alb levels were significantly less likely to self-report depression or anxiety after adjustment (p = 0.009, p = 0.005, p = 0.003, and p = 0.005, respectively). Additionally, we found an association between lower levels of albumin and self-reported problems with mobility or usual activities (p = 0.01). We also found associations between better muscle strength and higher levels of vitamin D, calcium, phosphorous, and albumin (p = 0.006, p = 0.003, p = 0.004 and p = 0.002, respectively). Overall, our data provide evidence that serum vitamin D and Alb levels are negatively related to self-reported anxiety or depression, usual activities, mobility, and three dimensions of QoL in older adults. Furthermore, vitamin D levels are positively related to hand grip strength in adults over 65 years old.

Candidate gene studies have analyzed the effect of specific vitamin D pathway genes on vitamin D availability; however, it is not clear whether genetic variants also affect overall bone metabolism. This study evaluated the association between genetic polymorphisms in GC, CYP2R1 and CYP24A1 and serum levels of total 25(OH)D, iPTH and other mineral metabolism biomarkers (albumin, total calcium and phosphorus) in a sample of 273 older Spanish adults. We observed a significant difference between CYP2R1 rs10741657 codominant model and total 25(OH)D levels after adjusting them by gender (p = 0.024). In addition, the two SNPs in the GC gene (rs4588 and rs2282679) were identified significantly associated with iPTH and creatinine serum levels. In the case of phosphorus, we observed an association with GC SNPs in dominant model. We found a relationship between haplotype 2 and 25(OH)D levels, haplotype 4 and iPTH serum levels and haplotype 7 and phosphorus levels. In conclusion, genetic variants in CYP2R1 and GC could be predictive of 25(OH)D and iPTH serum levels, respectively, in older Caucasian adults. The current study confirmed the role of iPTH as one of the most sensitive biomarkers of vitamin D activity in vivo.