Variation of Metabolite and Hormone Contents in Human Milk

Human milk (HM) is the optimal nutrition for infants born at term during the first months of life by itself and thereafter in combination with complementary feeding 1 and for preterm infants if fortified with protein and other nutrients. 2,3HM is a complex mixture of nutrients with variable composition.The energy content shows large interindividual variation from 50 to 86 kcal/100 mL (mean [M] AE 2 standard deviation [SD]), as determined in a recent meta-analysis. 4 The variance of the energy content primarily reflects high variation of the fat content but also protein and, to a lesser extent, lactose contents as shown in the analysis of 2554 expressed HM samples in Denmark (Table 1). 5Milk changes with duration of lactation, in particular protein content decreases (Fig. 1) whereas fat content increases. 6Other factors associated with variation in milk composition include duration of gestation, maternal diseases such as diabetes mellitus or malnutrition, genotype, and maternal diet. 7Energy and macronutrient supply to the breastfed term infant may modulate growth and body composition.For example, higher contribution of protein to total milk energy content at 4 to 8 weeks of lactation has recently been found to predict a higher body mass index at the age of 1 year (Fig. 2).