Effect of free vitamin D(2) drops on serum 25-hydroxyvitamin D in infants with immigrant origin: a cluster randomized controlled trial.

BACKGROUND/OBJECTIVE: To study whether a free supply of vitamin D(2) drops to 6-week-old infants together with tailor-made information handouts improves the vitamin D status after 7 weeks in the intervention group compared to a control group.

SUBJECTS/METHODS: In this cluster randomized controlled trial in eight child health clinics in Oslo, Norway, 66 healthy infants with Pakistani, Turkish or Somali background were included. The intervention group received daily supplementation of vitamin D drops containing 10 microg (400 IU) of ergocalciferol (vitamin D(2)) with a tailor-made information brochure about vitamin D and its sources, and instruction on how to administer the drops. They were compared to a control group receiving usual care. The principal outcome measure was increase in serum 25-hydroxyvitamin D (S-25OHD) 7 weeks later. S-25OHD was analyzed by high-performance liquid chromatography-ultraviolet-mass spectrometry.

RESULTS: Total 78% (n=51) of the included infants completed the study. At follow-up, S-25OHD was significantly higher in the intervention group than in the control group (93.5 versus 72.7 nmol l(-1), P=0.03). The mean increase in S-25OHD adjusted for baseline was 28 nmol l(-1) (95% confidence interval 10.9-45.2, P=0.002) higher in the intervention group than in the control group. Among exclusively breastfed infants at baseline, S-25OHD increased by 32.3 nmol l(-1) (P=0.035) in the intervention group compared to control group.

CONCLUSION: Free supply of vitamin D drops to 6-week-old infants together with tailor-made information handouts significantly improved the vitamin D status of infants with immigrant background compared to usual care.