Abstract
Human breast milk (BM) amino acid (AA) composition may be impacted by lactation stage or factors related to geographical location. The present cross-sectional study is aimed at assessing the temporal changes of BMAA over lactation stages in a large cohort of urban mothers in China. Four hundred fifty BM samples, collected in three Chinese cities covering eight months of lactation were analyzed for free (FAA) and total (TAA) AA by o-phthalaldehyde/ fluorenylmethylchloroformate (OPA/FMOC) derivatization. Concentrations and changes over lactation were aligned with previous reports. Both the sum and the individual TAA values significantly decreased during the first periods of lactation and then generally leveled off. Leucine and methionine were respectively the most and the least abundant indispensable amino acids across all the lactation stages, whereas glutamic acid + glutamine (Glx) was the most and cystine the least abundant dispensable AA. The contribution of FAA to TAA levels was less than 2%, except for free Glx, which was the most abundant FAA. In conclusion, the AA composition of the milk from our cohort of urban Chinese mothers was comparable to previous studies conducted in other parts of the world, suggesting that this is an evolutionary conserved trait largely independent of geographical, ethnic, or dietary factors.
Highlights
Evolution has shaped the composition of breast milk to ensure optimal development of healthy term offspring
In this cross-sectional study, total amino acid (TAA) and free amino acids (FAA) were quantified in 450 breast milk samples collected at different stages from early to late lactation in healthy urban Chinese women
Weight, BMI, mode of delivery were significantly different among the lactation stage cohorts
Summary
Evolution has shaped the composition of breast milk to ensure optimal development of healthy term offspring. Breast milk composition is not constant and appears to be affected by multiple factors, including lactation stage, mothers’ genetic background and diet, gestational age at delivery, or geographical location [1]. Breast milk protein is a key nutrient supporting body growth and organ development during the first few months of life by providing nitrogen and indispensable amino acids (IAA) required for body protein building and by stimulating the secretion of growth-promoting hormones (i.e., insulin, insulin-like growth factor (1-IGF1)). Emerging evidence suggests that the relatively low levels of protein and insulinotropic amino acids in breast milk may be protective against the development of metabolic disorders later in infant life [2].
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