Vitamin D in Somali women living in Sweden

Abstract

Introduction: Sunlight is the major source of Vitamin D synthesis. Information regarding vitamin D, bone status and general health in Somali women living in Sweden is limited. Vitamin D binding protein (DBP) is the major carrier of most vitamin D metabolites. It is not clear whether DBP is genetically determined or influenced by external factors. Aim: To characterize vitamin D status, effect of vitamin treatment and possible comorbidity in Somali women living in Sweden. Methods: Somali women (n=114), age range 18-56 years, residing in Sweden since at least 2 years (range 2-23) were recruited on voluntary basis. They were randomized to different treatment arms, vitamin D drops, 800 IU, 1600 IU or placebo daily, as well as UVB light or Woods lamp (placebo light), respectively. Blood samples were collected at start and every 6th weeks during the intervention (3 months) and follow-up (3 months). Bone Mineral Density (BMD) was examined. A random population sample, WHO MONICA study, Gothenburg, was used as controls. Results: Vitamin D deficiency, i.e. serum (S)-25(OH)D<25 nmol/l, was found in 73% of Somali women. S-25(OH)D increased dose dependently compared to placebo. At least 1600 IU of vitamin D3 daily was needed to raise S-25(OH)D values to a sufficient range (>50 nmol/l). S-DBP was lower in Somali women than in native Swedish women of whom <2% had vitamin D deficiency. There was a positive correlation between S-25(OH)D and S-DBP values in Swedish women. S-DBP was not affected by vitamin D treatment in Somali women. Somali women had lower lumbar BMD values compared with American white women and both lumbar and femoral BMD were lower than the Afro-American women using the reference provided by the Dual energy X-ray Absorptiometry manufacturer. Comorbidity, as fractures, hypothyroidism, diabetes mellitus and hypertension, was similar in Somali women and native Swedes. However, use of allergy medications was higher, and health related quality of life, especially the physical component, was lower than in native Swedish women. Conclusion: Vitamin D deficiency was common, 73%, in Somali women living in Sweden. Vitamin DBP and BMD were lower than in controls. S-DBP was related to vitamin D status but unaffected by age, sex and vitamin D treatment. At least 1600 IU vitamin D was needed to reach sufficient levels of S-25(OH) D. It is important to follow the Somali population at the northern latitude in order to prevent from osteomalacia.