Vitamin D status and variable responses to supplements depend in part on genetic factors in adults with cystic fibrosis.

Vitamin D sufficiency has been difficult to achieve consistently in patients with cystic fibrosis (CF), even with robust oral supplements. To assess vitamin D status and resistance to supplementation, we studied 80 adults using 25-hydroxyvitamin D (25OHD) determinations and whole genome sequencing to construct polygenic risk scores (PRS) that aggregate variants associated with vitamin D status. The results revealed that 30 % of patients were below the threshold of 30 ng/mL and thus should be regarded as insufficient despite normal vitamin E status, a reflection of adherence to fat soluble vitamin supplementation. The PRS values were significantly correlated with 25OHD concentrations, confirming our results in children with CF, and indicating that genetic factors play a role and have implications for therapy.