Calcium dialysability as an estimation of bioavailability in human milk, cow milk and infant formulas

The calcium dialysability of human milk, cow milk and infant formulas is estimated by applying the in vitro method (Miller, Schricker, Rasmussen, & Van Campen, (1981). American Journal of Clinical Nutrition, 34, 2248–2256) slightly modified, as a measure of its bioavailability. The influence of the protein composition of infant formula samples on calcium bioavailability is also studied. Whole cow milk, a pool of human milk and 18 commercial infant formulas of 6 different types are analysed. The highest values of calcium dialysability (mg Ca/100 ml infant formula) correspond to premature (13.6) and follow-up formulas (11.8) and the lowest ones to adapted formulas (3.7); the latter values are similar to that of human milk (4.0). The highest value corresponds to cow milk (18.9). In relation to the possible influence of the protein fraction on calcium dialysability, it is higher in formulas in which casein is the main protein fraction and in protein hydrolysates than in other formulas, although these formulas are also the ones with the highest calcium content. Content is the factor that most influences dialysability.