title: Effect of vitamin D3 supplementation on iron status: a randomized, double-blind, placebo-controlled trial among ethnic minorities living in Norway.
abstract: Both vitamin D and iron deficiencies are widespread globally, and a relationship between these deficiencies has been suggested. However, there is a paucity of randomised controlled trials assessing the effect of vitamin D supplementation on iron status.
  
  
  
  We aimed to investigate whether 16 weeks of daily vitamin D3 supplementation had an effect on serum ferritin, haemoglobin, serum iron and transferrin saturation.
  
  
  
  Overall, 251 participants from South Asia, Middle East and Africa aged 18-50 years who were living in Norway were randomised to receive daily oral supplementation of 10 μg vitamin D3, 25 μg vitamin D3, or placebo for 16 weeks during the late winter. Blood samples from baseline and after 16 weeks were analysed for serum 25-hydroxyvitamin D (s-25(OH) D), serum ferritin, haemoglobin and serum iron. In total, 214 eligible participants completed the intervention (86 % of those randomised). Linear regression analysis were used to test the effect of vitamin D3 supplementation combined (10 or 25 μg) and separate doses 10 or 25 μg compared to placebo on change (T2-T1) in each outcome variable adjusted for baseline s-25(OH)D values.
  
  
  
  There was no difference in change in the levels of s-ferritin (1.9 μg/L, 95 % CI: -3.2, 7.0), haemoglobin (-0.02 g/dL, 95 % CI: -0.12, 0.09), s-iron (0.4 μg/L, 95 % CI: -0.5, 1.3) or transferrin saturation (0.7 %, 95 % CI: -0.6.1, 2.0) between those receiving vitamin D3 or those receiving placebo. Serum 25-hydroxyvitamin D increased from 29 nmol/L at baseline to 49 nmol/L after the intervention, with little change in the placebo group.
  
  
  
  In this population of healthy ethnic minorities from South Asia, the Middle East and Africa who had low vitamin D status, 16 weeks of daily supplementation with 10 or 25 μg of vitamin D3 did not significantly affect the haemoglobin levels or other markers of iron status.
authors: Department of Community Medicine, Institute of Health and Society, University of Oslo, Oslo, Norway. a.a.madar@medisin.uio.no.
authors: Ahmed A
authors: AA
authors: Madar
authors: Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway.
authors: Lars C
authors: LC
authors: Stene
authors: Department of Community Medicine, Institute of Health and Society, University of Oslo, Oslo, Norway.|Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway.
authors: Haakon E
authors: HE
authors: Meyer
authors: Department of General Practice, Institute of Health and Society, University of Oslo, Oslo, Norway.
authors: Mette
authors: M
authors: Brekke
authors: Department of General Practice, Institute of Health and Society, University of Oslo, Oslo, Norway.
authors: Per
authors: P
authors: Lagerløv
authors: Department of General Practice, Institute of Health and Society, University of Oslo, Oslo, Norway.
authors: Kirsten V
authors: KV
authors: Knutsen
mesh_terms: D000293:Adolescent; D000328:Adult; D018798:Anemia, Iron-Deficiency / Q000097:blood / Q000208:ethnology*; D001208:Asia / Q000208:ethnology; D002097:C-Reactive Protein / Q000378:metabolism; D002762:Cholecalciferol / Q000008:administration & dosage*; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005006:Ethnicity; D005260:Female; D005293:Ferritins / Q000097:blood; D005492:Folic Acid / Q000097:blood; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007501:Iron / Q000097:blood*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008877:Middle East / Q000208:ethnology; D009664:Norway / Q000453:epidemiology; D009752:Nutritional Status; D014168:Transferrin / Q000378:metabolism; D014805:Vitamin B 12 / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000208:ethnology*; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D014168:Transferrin; D002762:Cholecalciferol; D002097:C-Reactive Protein; D005293:Ferritins; D005492:Folic Acid; D007501:Iron; D014805:Vitamin B 12
keywords: Immigrants; Iron status; Randomised controlled trials; Vitamin D