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

Summary 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/cm 2 ) 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.