RESUMEN
BACKGROUND: Vitamin D insufficiency is a risk factor for multiple sclerosis (MS), and patients do not always show the expected response to vitamin D supplementation. OBJECTIVE: We aimed to determine if vitamin D supplementation leads to a similar increase in serum 25-hydroxyvitamin-D (25(OH)D) levels in patients with MS and healthy controls (HCs). METHODS: Participants in this open-label study were female, white, aged 18-60 years, had 25(OH)D levels ⩽ 75 nmol/l at screening, and had relapsing-remitting MS (RRMS) or were HCs. Participants received 5000 IU/day of vitamin D3 for 90 days. Utilizing generalized estimating equations we examined the relationship between the primary outcome (serum 25(OH)D level) and the primary (MS versus HC status) and secondary predictors. RESULTS: For this study 27 MS patients and 30 HCs were enrolled. There was no significant difference in baseline 25(OH)D level or demographics except for higher body mass index (BMI) in the MS group (25.3 vs. 23.6 kg/m(2), p=0.035). In total, 24 MS subjects and 29 HCs completed the study. In a multivariate model accounting for BMI, medication adherence, and oral contraceptive use, MS patients had a 16.7 nmol/l (95%CI: 4.2, 29.2, p=0.008) lower increase in 25(OH)D levels compared with HCs. CONCLUSIONS: Patients with MS had a lower increase in 25(OH)D levels with supplementation, even after accounting for putative confounders.