Comparison of the effect of daily versus bolus dose maternal vitamin D supplementation on the 24,25-dihydroxyvitamin D to 25-hydroxyvitamin D ratio.

OBJECTIVE

Supplementing lactating mothers with high doses of vitamin D can adequately meet vitamin D requirements of the breastfed infant. We compared the effect of bolus versus daily vitamin D dosing in lactating mothers on vitamin D catabolism. We hypothesized that catabolism of 25(OH)D to 24,25(OH)D would be greater in the bolus than in the daily dose group.

DESIGN, SETTING AND PATIENTS: Randomized controlled trial (clinicaltrials.govNCT01240265) in 40 lactating women.

INTERVENTIONS

Subjects were randomized to receive vitamin D orally, either a single dose of 150,000IU or 5000IU daily for 28days. Vitamin D metabolites were measured in serum and breast milk at baseline, 1, 3, 7, 14 and 28days.

MAIN OUTCOME MEASURE

Temporal changes in the serum 24,25(OH)D/25(OH)D ratio.

RESULTS

The concentration of serum 24,25(OH)D was directly related to that of 25(OH)D in both groups (r=0.63; p<0.001). The mean (±SD) 24,25(OH)D/25(OH)D ratio remained lower at all time points than baseline values in the daily dose group (0.093±0.024, 0.084±0.025, 0.083±0.024, 0.080±0.020, 0.081±0.023, 0.083±0.018 at baseline, 1, 3, 7, 14, and 28days, respectively). In the single dose group, the increase in 24,25(OH)D lagged behind that of 25(OH)D, but the 24,25(OH)D/25(OH)D values (0.098±0.032, 0.067±0.019, 0.081±0.017, 0.092±0.024, 0.103±0.020, 0.106±0.024, respectively) exceeded baseline values at 14 and 28days and were greater than the daily dose group at 14 and 28days (p=0.003). The 24,25(OH)D/25(OH)D ratio remained in the normal range with both dosing regimens. Greater breast milk vitamin D values in the single dose group were inversely associated with the 24,25(OH)D/25(OH)D ratio (r=0.14, p<0.001), but not with daily dosing.

CONCLUSIONS

After a 14-day lag, a single high dose of vitamin D led to greater production of 24,25(OH)D, presumably via induction of the 24-hydroxylase enzyme (CYP24A1), relative to the 25(OH)D value than did daily vitamin D supplementation, and this effect persisted for at least 28days after vitamin D administration. A daily dose of vitamin D may have more lasting effectiveness in increasing 25(OH)D with lesser diversion of 25(OH)D to 24,25(OH)D than does larger bolus dosing.