Vitamin D dose‐response study in breast fed infants from Montréal, Canada: 400 IU/day is sufficient to meet the plasma 25‐hydroxy vitamin D threshold of 50 nmol/L but not 75 nmol/L by 12 months of age

The Adequate Intake of 400 IU/d of vitamin D was established by the Institute of Medicine (IOM) to support 25‐hydroxyvitamin D (25(OH)D) concentrations >50 nmol/L whereas, the Canadian Paediatric Society suggests 75–225 nmol/L. We aimed to identify a dosage of vitamin D which would support 25(OH)D ≥75 nmol/L in 97.5% of participants across infancy. Healthy, term infants (n=132) were randomized to oral supplements of 400, 800, 1200 or 1600 IU vitamin D 3 daily from 1 to 12 mo of age and plasma 25(OH)D was measured (LC‐MS/MS; Warnex Inc.) (NCT00381914). The 1600 IU/d group was discontinued due to 25(OH)D concentrations >225 nmol/L. At each time point, logistic regression was used to test the effect of dose vs. 400 IU/d by ITT. Compared to the 400 IU group, dose significantly predicted (*) achieving ≥75 nmol/L, with odds ratios (CI) of 15(3–73) at 2 mo, 13(2–76) at 3 mo, 5(1–17) at 12 mo for 1200 IU/d and 16(2–128) for 1600 IU/d. By 3 mo, the 400 IU/dosage meet the IOM recommendation. If 75 nmol/L is the threshold, then dosages >400 IU/d may be necessary. Functional outcomes may be improved with 25(OH)D levels ≥75 nmol/L. Percent of infants ≥ 50 and 75 nmol/L by age and group compared to 400 IU/d at same timeAge (mo) 400 IU/d (n=39) 800 IU/d (n=39) 1200 IU/d (n=38) 1600 IU/d (n=16) ≥50 ≥75 ≥50 ≥75 ≥50 ≥75 ≥50 ≥751 66 17 61 21 76 34 82 27 2 92 42 90 57 93 87 * 92 77 3 97 55 97 81 96 93 * 100 100 6 100 71 93 73 100 87 100 100 9 97 66 96 68 100 69 100 86 12 97 38 96 63 100 68 * 100 83 ** p<0.05.Grant Funding Source : Canadian Institutes of Health Research; Nutricia Research Foundation