Sunlight exposure or vitamin D supplementation for vitamin D-deficient non-western immigrants: a randomized clinical trial

Summary Vitamin D deficiency is very common in nonwestern immigrants. In this randomized clinical trial, vitamin D 800 IU/day or 100,000 IU/3 months were compared with advised sunlight exposure. Vitamin D supplementation was more effective than advised sunlight exposure in improving vitamin D status and lowering parathyroid hormone levels. Introduction Vitamin D deficiency (25-hydroxyvitamin D [25(OH)D]<25 nmol/l) is common among non-western immigrants. It can be treated with vitamin D supplementation or sunlight exposure. Methods To determine whether the effect of vitamin D3 supplementation (daily 800 IU or 100,000 IU/3 months) or sunlight exposure advice is similar with regard to serum 25(OH)D and parathyroid hormone (PTH) concentrations. Randomized clinical trial in 11 general practices in The Netherlands. Non-western immigrants, aged 18–65 years (n=232) and serum 25(OH)D<25 nmol/l were randomly assigned to supplementation (daily 800 IU or 100,000 IU/ 3 months) or advice for sunlight exposure for 6 months (March–September). Blood samples were collected at baseline, during treatment (3 months, 6 months), and at follow-up (12 months). Statistical analysis was performed with multilevel regression modelling. Results The intention-to-treat analysis included 211 persons. Baseline serum 25(OH)D was 22.5±11.1 nmol/l. After 6 months, mean serum 25(OH)D increased to 53 nmol/l with 800 IU/day, to 50.5 nmol/l with 100,000 IU/3 months, and to 29.1 nmol/l with advised sunlight exposure (supplementation vs sunshine p<0.001). Serum PTH decreased significantly in all groups after 3 months, more in the supplementation groups than in the advised sunlight group (p<0.05). There was no significant effect on physical performance and functional limitations. Conclusion Vitamin D supplementation is more effective than advised sunlight exposure for treating vitamin D deficiency in non-western immigrants.