Background: Vitamin A supplementation of mothers postpartum may improve infant health, not only by increasing vitamin A delivery to the infant through breast milk but also by increasing delivery of milk immune factors. Our hypothesis was that postpartum supplementation with vitamin A increases milk concentrations of certain soluble immune factors.
Design: In a double-blind trial conducted in Matlab, Bangladesh, women at 1-3 wk postpartum were randomly assigned to receive until 9 mo postpartum 1) a single dose of 60 mg retinol as retinyl palmitate followed by daily placebos (n = 69), 2) daily doses of 7.6 mg beta-carotene (n = 72), or 3) daily placebos (n = 71). Milk samples collected at baseline and 3 mo postpartum were analyzed by enzyme-linked immunosorbent assay for secretory immunoglobulin A, lactoferrin, lysozyme, and interleukin 8; by HPLC for total retinol; and by atomic absorption spectroscopy for sodium and potassium.
Results: After mammary epithelial permeability (defined as an elevated Na:K) and baseline immune factor concentrations were controlled for, there were no significant treatment effects on immune factors at 3 mo. Increased mammary permeability was common (25% of women at baseline and 12% at 3 mo) and was associated with higher concentrations of milk immune factors. Low body vitamin A stores at baseline, as assessed by the modified-relative-dose-response test, were associated with a higher Na:K, but neither retinol nor beta-carotene supplementation affected the prevalence of increased mammary permeability.
Conclusions: Postpartum vitamin A supplementation does not increase milk concentrations of immune factors. The causes of increased mammary epithelial permeability in this population require further study.