A Comparison between Severity-dependent Protocol and Fixed Dose Regimen of Oral Vitamin D Supplementation on Correction of Hypovitaminosis D among Dialysis Patients.

Background: Low vitamin D status is associated with either low muscle mass or impaired muscle function in dialysis patients. However, there is no consensus on how best to correct hypovitaminosis D, defined as serum 25-hydroxyvitamin D [25(OH)D] level <30 ng/mL, in patients with end-stage kidney disease (ESKD). This study investigated the effect of different vitamin D supplementation regimens on sarcopenia outcomes in dialysis patients.

Methods: This was a prospective randomized controlled trial. ESKD patients treated with maintenance hemodialysis (HD) or peritoneal dialysis (PD) with low vitamin D status on a ratio of 1:1, randomized to either receive oral ergocalciferol utilizing a severity-dependent treatment protocol for low vitamin D status suggested by the K/DOQI as a control group, or a fixed-dose regimen of 20,000 international units (IU)/week. The changes in muscle mass were measured by bioimpedance spectroscopy (BIS), muscle strength was assessed by a hand grip dynamometer, physical performance was determined by gait speed, and muscle-related biomarkers were examined.

Results: A total of 76 dialysis patients were randomized (HD=43.4%). Baseline characteristics, including age, dialysis vintage, and muscle parameters were similar. After supplementation, the average serum 25(OH)D levels in the severity-dependent and fixed-dose groups were significantly elevated from 14.5±7.3 to 27.2±13.2 ng/mL, p<0.001 and from 15.1±6.4 to 28.8±11.5 ng/mL, p<0.001, respectively, and did not differ between groups at six months (p=0.60). Despite comparable energy and protein intake, the mean BIS-derived total-body muscle mass normalized to height squared was significantly increased at six months in the fixed-dose group (14.5±3.3 to 15.3±3.0 kg/m², p=0.03) compared with the severity-dependent protocol (13.5±2.7 to 13.7±2.9 kg/m², p=0.58). In the subgroup analysis, muscle mass improvement was statistically elevated in PD patients (p=0.01) while unaltered among HD patients (p=0.88) in the fixed-dose group. Muscle strength, gait speed, and serum insulin-like growth factor-1 level, as the mediators of muscle cell growth, were not different between the two groups at six months (p>0.05). Neither hypercalcemia nor hyperphosphatemia was found throughout the study.

Conclusion: A fixed-dose ergocalciferol supplementation demonstrates similar performance in the correction of low vitamin D status but better muscle mass improvement than a severity-dependent protocol among ESKD patients. Regular dosing intervals of weekly vitamin D supplementation appear to be a promising treatment for sarcopenia among patients undergoing dialysis.