Vitamin D treatment in Somali women living in Sweden – Two randomized, placebo-controlled studies

Abstract

Objective: There is limited information about the prevalence of vitamin D deficiency and the effects of treatment on immigrants. The effects of oral vitamin D intake and UVB treatment on vitamin D status in healthy Somali women living in Sweden were analysed. Design: Two studies were carried out; a randomized, double-blind, placebo-controlled study, with oral drops of 800 IU and 1600 IU cholecalciferol and similar amounts of placebo given daily during 12 weeks and a single-blind, placebo-controlled study, using UVB (4·3–8·7 J/cm2) or Woods lamp (placebo) on the upper body, or the face and hands. Patients: One-hundred fourteen Somali women, mean age 34 years, latitude 0–10°N, living in Sweden >2 years, latitude 57°N, participated. Measurements: Serum 25-hydroxyvitamin D (S-25(OH)D) was monitored before, every 6 weeks and at 3 months after treatment. Results: The majority of the women (n = 83, 73%) were vitamin D-deficient, S-25(OH)D < 25 nmol/l at start. There was a dose-dependent increase in S-25(OH)D levels (P = 0·001, stratified Jonckheere–Terpstra test) with a mean increase after twelve weeks in women treated with 800 IU/day and women treated with 1600 IU/day of 18 nmol/l (95% CI: 6–29, median = 17) and 29 nmol/l (95% CI: 17–42, median = 34), respectively. S-25(OH)D decreased during follow-up but remained above baseline levels. The placebo group remained unchanged throughout the study. UVB treatment increased S-25(OH)D dose-dependently after 6 weeks (P = 0·03, Jonckheere–Terpstra test). Conclusions: Vitamin D deficiency was common in immigrants living at higher latitudes. Vitamin D treatment increased S-25(OH)D levels dose-dependently during 3 months. The effect was maintained for another 3 months. At least 1600 IU/day is recommended. The dropout rate was high.