Water-soluble vitamin D in human milk: A myth

Earlier reports on the presence of vitamin D sulfate in human milk, and on positive biological activity of this material in rodents, were assessed in view of recent contradictory findings. Analyses of vitamin D in human milk over the past 50 years showed an average activity of 20 IU/liter, while further studies indicated that there were large quantities of vitamin D sulfate in human milk, and that the sulfate had biologic activity in rats. Earlier findings were based on a non-specific analysis method for vitamin D sulfate. Recent studies with highly purified vitamin D sulfate have shown that there are negligible amounts of vitamin D sulfate in the whey fraction of human milk. The purified sulfate had less than 5% of the biologic activity of vitamin D3 for mobilizing calcium from bone in vitamin D-deficient rats (less than 1% of the activity in supporting bone calcification or stimulating intestinal transport of calcium). It is concluded that there is no significant vitamin D sulfate in human milk and that the sulfate has virtually no biologic activity caompared to vitamin D3. This new evidence should be considered in regard to vitamin D supplementation of breast-fed infants. (wz)