Maternal supplements can provide breast milk with adequate vitamin D

Breastfeeding mothers can supply enough vitamin D in their milk to satisfy their infants’ requirements by taking 6400 IU of vitamin D each day, a 6-month randomized trial among mothers of exclusively breastfed babies showed. This finding suggests an alternate strategy to the direct infant vitamin D supplementation long recommended by the AAP.

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Investigators divided mother-infant pairs at 4 to 6 weeks postpartum into 3 treatment groups, with the mothers receiving either 400, 2400, or 6400 IU vitamin D₃ each day. In addition, infants in the 400 IU group received oral 400 IU vitamin D₃/day, while infants in the 2400 and 6400 IU group received placebo. Each month, investigators evaluated mothers and infants with maternal blood samples and urine samples; vitamin D deficiency was defined as 25-hydroxy-vitamin D (25[OH]D) <50nmol/L. Investigators restricted final comparisons to the 400 IU and 6400 IU treatment groups, discontinuing  the 2400 IU group because of infant safety concerns. Of the remaining 216 exclusively and fully breastfeeding mother-infant pairs, 148 (64.7%) continued to exclusively/fully breastfeed through the fourth month, and 95 (28.4%) completed the full 6 months.

Among infants fully breastfed through the fourth month or the entire study period, those whose only source of vitamin D was maternal (the 6400 IU group) did not differ from infants who received oral supplementation of 400 IU/day (the 400 IU group) on any of the laboratory parameters tested-including not only vitamin D, but infant serum calcium, creatinine, and phosphorus. Investigators also found no differences between the 2 treatment groups in infant weight, length, and head circumference at any of the visits, even after controlling for race/ethnicity. Vitamin D deficiency was greatly affected by race, however, with African-American mothers and infants having substantially lower circulating 25(OH)D levels than white participants at baseline (Hollis BW, et al. Pediatrics. 2015;136[4]:625-634).

Commentary: The authors cite earlier studies that showed compliance rates for supplementing breastfed infants with vitamin D ranges from 2% to 19%. I wonder if mothers are more likely to comply with taking the vitamin D themselves if they know that by doing so they will be treating their babies. If so, we are likely to see more information on this approach.

Ms Freedman is a freelance medical editor and writer in New Jersey. Dr Burke, section editor for Journal Club, is chairman of the Department of Pediatrics at Saint Agnes Hospital, Baltimore, Maryland. The editors have nothing to disclose in regard to affiliations with or financial interests in any organizations that may have an interest in any part of this article.