Can we define an infant's need from the composition of human milk?

Human milk is recommended as the optimal nutrient source for infants and is associated with several short- and long-term benefits for child health. When accepting that human milk is the optimal nutrition for healthy term infants, it should be possible to calculate the nutritional needs of these infants from the intake of human milk. These data can then be used to design the optimal composition of infant formulas. In this review we show that the composition of human milk is rather variable and is dependent on factors such as beginning or end of feeding, duration of lactation, diet and body composition of the mother, maternal genes, and possibly infant factors such as sex. In particular, the composition of fatty acids in human milk is quite variable. It therefore seems questionable to estimate the nutritional needs of an infant exclusively from the intake of human milk. The optimal intake for infants must be based, at least in part, on other information-eg, balance or stable-isotope studies. The present recommendation that the composition of infant formulas should be based on the composition of human milk needs revision.