Vitamin D supplementation and status in infants: a prospective cohort observational study.

OBJECTIVE: Vitamin D status in infants depends on supplementation. We examined the vitamin D status in relation to supplementation dose and scheme in infants. PATIENTS AND METHODS: One hundred thirty-four infants age 6 months and 98 infants age 12 months (drop out 27%) were investigated. Vitamin D intake (diet, supplements), anthropometry, and 25-hydroxyvitamin D (25-OHD) serum concentration at the 6th and 12th months were assessed. RESULTS: Vitamin D intake of 1062 ± 694 IU at the 6th month was not different from that at the 12th month (937 ± 618 IU). Vitamin D intake expressed in international units per kilogram of body weight decreased from 141 ± 80 IU/kg at the 6th month to 93 ± 62 IU/kg at the 12th month (P < 0.0001), which was associated with a reduction in 25-OHD from 43 ± 20 ng/mL to 29 ± 12 ng/mL, respectively (P < 0.0001). In the subgroup of everyday supplemented infants (n = 43), vitamin D intake decreased from 143 ± 88 IU/kg at the 6th month to 118 ± 60 IU/kg at the 12th month (P < 0.05), which coincided with a reduction of 25-OHD from 40 ± 19 ng/mL to 32 ± 13 ng/mL (P < 0.01). In the subgroup with variable supplementation habits (n = 32), vitamin D intake decreased from 146 ± 79 IU/kg to 77 ± 56 IU/kg (P < 0.001), which was associated with a reduction of 25-OHD from 42 ± 21 ng/mL to 25 ± 8 ng/mL (P < 0.0001). 25-OHD concentration change between the 6th and the 12th months negatively correlated with the 25-OHD level assessed at the 6th month (r = -0.82; P < 0.0001). CONCLUSIONS: Vitamin D supplementation of infants should consider their rapid body weight increment. We postulate vitamin D daily dose close to 100 IU/kg body weight as favorable for infants up to age 12 months.