Calcidiol in human milk. The effect of prohormone on vitamin D status of breast fed unsupplemented infants.

Vitamin D, free or sulfoconjugated, and calcidiol (25(OH)vitamin D) levels were measured by competitive binding assay in breast milk samples of nursing mothers. Vitamin D status of their unsupplemented breast fed infants was determined. A strong correlation was established during the first month of the infant life only between calcidiol mother milk content and breast-fed infant serum. Calcidiol seems to be the vitamin D derivative mainly responsible for the maintainance of the vitamin D status of the newborn infant.