Vitamin D insufficiency and treatment with oral vitamin D3 in northern-dwelling patients with chronic kidney disease.

Vitamin D insufficiency is common in people living at northern latitudes and those with chronic kidney disease (CKD). We studied persons with both of these risk factors to determine the prevalence of vitamin D insufficiency and whether serum 25-hydroxyvitamin D (25(OH)D) levels were affected by oral vitamin D3 supplementation.This was a prospective controlled trial of 128 patients with stage 3-5 non-dialysis dependent CKD. Patients were assigned to the intervention (oral vitamin D3 1,000 IU/day) in a 1:1 ratio at the discretion of the attending dietitian. Serum biochemical markers were measured at baseline (May-July) and after 3 months of follow-up. There were 63 control and 65 intervention subjects.Mean 25(OH)D levels increased significantly higher in the treatment group (mean increase from baseline: 10.3+/-10.4 ng/mL vs. 0.8+/-6.8 ng/mL, p<0.0001). This difference remained significant after adjustment for differing baseline characteristics between groups (p<0.0001). Treatment with oral vitamin D3 reduced vitamin D insufficiency by 37%, as compared with a 2% increase in prevalence among the control group (p<0.0001). Considering the entire study population, 93% of patients had levels less than <30 ng/mL at least once during the study.Vitamin D insufficiency is highly prevalent in northern-dwelling patients with stage 3-5 CKD, and is moderated by oral supplementation with 1,000 IU of vitamin D3 daily.