Effects of milk and milk components on calcium, magnesium, and trace element absorption during infancy

During early life, infants usually consume a diet that is heavily dominated by milk. It is generally believed that breast-fed infants absorb adequate quantities of minerals and trace elements, whereas there is some concern about how well infants can utilize these nutrients from cow's milk formula and other infant diets. Therefore, most infant formulas contain much higher concentrations of minerals and trace elements than those of breast milk. Our knowledge of how infants can utilize these nutrients from different diets is very limited. This paper critically reviews the effects of various components in breast milk, cow's milk, and infant formula and how they either facilitate or inhibit the absorption of minerals and trace elements. Particular emphasis is put on milk proteins such as lactoferrin, casein, and whey proteins, but phytate in soy formula is also discussed. Competition among minerals for absorptive pathways as well as other nutrient-nutrient interactions are considered in the context of infant nutrition. The difficulties involved in assessing mineral and trace element status in infants, as well as the potential consequences of suboptimal and excessive intakes of calcium, magnesium, iron, zinc, copper, manganese, and selenium are also discussed, particularly in the light of infant requirements.