Vitamin-D in human milk.

The vitamin-D concentration in human milk is reported to be very low, yet breast-fed infants do not develop rickets. All the earlier assays of vitamin D were made on the lipid fraction of milk, and the aqueous phase was discarded. It is now clear that most of the vitamin D in human milk is present as a water-soluble conjugate of vitamin D with sulphate. The concentration of vitamin-D sulphate in the aqueous fraction of human milk collected at different stages of lactation has been chemically measured. Milk was collected from twenty-two women 3-8 days post partum and fourteen women 4-6 weeks post partum. The vitamin-D sulphate concentration in milk collected between the 3rd and 5th days was 1-78 mug/dl, significantly higher that the 1-00 mug/dl for milk collected between the 6th and 8th days. After the 8th day there was no significant change.