Changes in Human Milk Composition During the Initiation of Lactation

Abstract

Summary Studies were undertaken to determine the progressive changes and relationships between the major constituents in the mammary secretion of breast feeding and non‐breast feeding women during the initiation of lactation. The concentration of metabolites (lactose, glucose and urea), electrolytes and proteins (total protein, α‐lactalbumin, lactoferrin, albumin. IgA, IgG and IgM) were measured in small samples of mammary secretion (0·5‐5·0 ml). Colostrum during late pregnancy contained higher concentrations of proteins and lower concentrations of metabolites than milk in established lactation. Of the electrolytes, the concentrations of sodium, chloride and magnesium were higher, whereas potassium and calcium were lower in colostrum than in milk. The osmolality of the secretion remained relatively constant over the pre‐partum and post‐partum period. These findings showed that the initiation of lactation developed in two phases, first a limited secretion of milk constituents in late pregnancy and then true induction of lactation (lactogenesis) 32‐40 h after delivery. The changes in the mammary secretion of non‐breast feeding women during the first 3 days post‐partum were similar to those observed in breast feeding women but reversed abruptly during the next 6 days, indicating the onset of mammary involution. This finding demonstrated that breast feeding is not a major factor for the initiation of lactation but is essential for the continuation of full lactation.

Comparison of Mammary Gland Function During the Ovulatory Menstrual Cycle and Acute Breast Inflammation in Women

“…K and Cl were measured in the milk by the methods described previously (Hartmann and Prosser, 1982). The concentration of lactose, glucose and albumin and the osmolality of the milk were measured by the methods described by Kulski and Hartmann (1981). The total protein content of the milk was defermined by a modification of tbe l.owry assay as described by Healy et al (1980).…”

Physiology of milk secretion

“…Colostrum is produced during the first 4 days postpartum, followed by a 10e15 days period of transitional milk secretion, before copious production of mature milk (after 15 days) [8]. Milk composition is dramatically altered: sodium and chloride concentrations fall while those of lactose, immunoglobulins A (IgA), lactoferrin (LTF) and other components of mature milk increase.…”

“…During lactogenesis I, MECs differentiate morphologically and become competent to produce and secrete some milk components referred as colostrum [8], due to the activation of the expression of some milk protein genes and biosynthetic enzymes, as well as the production of lactose and accumulation of lipid droplets (LDs) [6]. However, production and secretion of milk components appear to be restricted to a limited number of alveolar MECs with incompletely developed secretory mechanisms.…”

Adipose tissue development during early life: novel insights into energy balance from small and large mammals

“…Then even after this stage of lactation, the fat content remains around three times higher than that of either sheep (34) or human subjects (35) . Protein concentrations are also elevated in rodents but, while these remain unchanged through lactation in the rat (33) they fall dramatically over the first 4 d of lactation in human breast milk (35) . This primarily reflects the very different composition of colostrum in human (and sheep) milk (36) compared with that of rodents and which is necessary for providing immune protection immediately after birth.…”

“…1 (34) 5 . 0 (35) promotes BAT thermogenesis (44) . These results have been confirmed in a mouse PRLR knockout model which demonstrated that BAT growth and development were severely impaired, as was the expression of a number of brown adipogenic genes including UCP1 (65) .…”