The breast contains a large variety of amino acids. Of these, whey protein accounts for 50 to 80% of the protein in breast milk. Nucleotides, which are building blocks of DNA, are conditionally essential during the first few weeks of a child’s life. Whey and casein proteins both aid in growth and development of the child. The corresponding amino acid profiles are discussed below. The most important factors influencing the breast’s composition are fullness and a mother’s age.
There are many factors that affect breast milk composition. The first is that the fat content of the milk may change by up to 2g/L over a 24-hour period. A recent meta-analysis of 26 studies found no correlation between vitamin A supplementation and breast milk fat content. Some women experience significant increases in retinol and a and b-carotene concentrations after supplementation with vitamin A, while others do not.
The composition of breast milk is highly variable. Despite the fact that it is a natural product, it contains many macronutrients that may not affect the child’s growth. The micronutrient composition of breast milk is not known, but research in this area suggests that it is plastic. However, the question of whether breast milk is adaptive to the needs of a child remains unanswered. This review notes that some studies do not include all the relevant variables, such as the type of collection and how many times the mother feeds the child.