The Effect of Maternal Vitamin D Supplementation on Vitamin D Status of Exclusively Breastfeeding Mothers and Their Nursing Infants: A Systematic Review and Meta-Analysis of Randomized Clinical Trials.

The optimal vitamin D supplementation plan during lactation is unclear. We investigated the effect of maternal vitamin D supplementation on mother-infant dyads' vitamin D status during lactation. All controlled trials that compared vitamin D supplements to placebo or low doses of vitamin D in breastfeeding mothers were included. Pooled effect size and the associated 95% CI for each outcome were estimated using random-effects models. A 1-stage random-effect dose-response model was used to estimate the dose-response relation across different vitamin D dosages and serum 25-hydroxy vitamin D [25(OH)D] concentrations. We identified 19 clinical trials with 27 separate comparison groups (n = 3337 breastfeeding mothers). Maternal vitamin D supplement dosages were associated with circulating 25(OH)D concentrations in breastfeeding women in a nonlinear fashion. Supplementation with 1000 IU of vitamin D/d increased serum 25(OH)D concentrations by 7.8 ng/mL, whereas there was a lower increase in concentrations at vitamin D doses of >2000 IU/d (3.07 and 2.05 ng/mL increases between 2000-3000 and 3000-4000 IU/d, respectively). A linear relation was observed between maternal vitamin D supplementation dosage and the infants' circulating 25(OH)D concentrations. Each additional 1000 IU of maternal vitamin D intake was accompanied by a 2.7 ng/mL increase in serum 25(OH)D concentration in their nursing infants. The subgroup analysis showed that maternal vitamin D supplementation was accompanied by a statistically significant increase in infants' 25(OH)D concentration in the trials with a duration of >20 wk, vitamin D supplementation >1000 IU/d, East Indian participants, maternal BMI <25 kg/m2, and studies with an overall low risk of bias. Long-term maternal supplementation with vitamin D at a high dose (>6000 IU/d) effectively corrected vitamin D deficiency in both mothers and infants. Nevertheless, infants with 25(OH)D concentrations over 20 ng/mL may require a relatively low maternal dose to maintain vitamin D sufficiency.