In Reply.—We appreciate the letter of Dr Özsoylu and agree that studies on the absorption of vitamin D and 25-OHD in human milk are needed. It might indeed be that absorption of vitamin D and its metabolites in human milk may be better than in formula. We would like to emphasize, however, that in the population we studied the serum 25-OHD concentrations were not found to be related to the milk concentrations; we speculated that this was due to the important effect of sunlight exposure on the vitamin D status of these infants, overwhelming any dietary effect.
Dr Özsoylu stated that the protective effect of vitamin D in milk may not be obvious in infants who had intrauterine vitamin D deficiency. We observed that the 25-OHD content of milk was correlated with the maternal serum concentration; therefore, mothers with low vitamin D status will have low milk vitamin D