Variation in the Protein Composition of Human Milk during Extended Lactation: A Narrative Review.

Sergio Verd,Antoni Gaya,Gemma Ginovart,Jaume Ponce-Taylor,Javier Calvo

doi:10.3390/nu10081124

Abstract

The aim of this review is to evaluate changes in protein parameters in the second year postpartum. There is considerable agreement among authors about the declining trend of human milk protein concentrations, but most research on protein content in breast milk focuses on the first year of life and comes from developed countries. Whereas this is the case for exclusive breastfeeding or for breastfeeding into the first year of life, the opposite applies to weaning or extended breastfeeding. This review is predominantly based on observational epidemiological evidence and on comparative research linking breast milk composition with cutting down on breastfeeding. Studies dating back several decades have shown an increase in the proportion of immunoglobulins, lactoferrin, and serum albumin during weaning. According to the limited data available, it seems likely that the regulation of milk protein composition during involution can be ascribed to alterations in tight junctions. In studies on humans and other mammalian species, offspring suckle more from mothers that produce more dilute milk and the increase in milk protein concentration is positively correlated to a decrease in suckling frequency during weaning. High milk protein contents were first reported in nonindustrial communities where breastfeeding is sustained the longest, but recent papers from urbanized communities have taken credit for rediscovering the increase in protein content of human milk that becomes evident with prolonged breastfeeding. This review presents an overview of the changes in breast milk protein parameters in the second year postpartum to enable milk banks’ practitioners to make informed nutritional decisions on preterm infants.

Highlights

The nutrient composition of human milk can be strongly influenced by the stage of lactation.These changes are consistent with consuming decreasing quantities of milk and ingesting other foods throughout the course of lactation as the infant matures [1]
The increased protein concentrations observed in prolonged breastfeeding suggest that donor milk from the weaning period may be more appropriate than early donor milk to meet the nutrient requirements calculated to achieve adequate growth rates among preterm infants when a mother’s own milk must be augmented with donor milk
This review has provided an estimation of the protein content with what is termed by Western definition prolonged lactation

Summary

Introduction

The nutrient composition of human milk can be strongly influenced by the stage of lactation. These changes are consistent with consuming decreasing quantities of milk and ingesting other foods throughout the course of lactation as the infant matures [1]. Whereas the concentration of lactose decreases fivefold during mammary involution, the concentration of proteins increases sixfold during this period [3]. It is worth highlighting the Nutrients 2018, 10, 1124; doi:10.3390/nu10081124 www.mdpi.com/journal/nutrients. The increased protein concentrations observed in prolonged breastfeeding suggest that donor milk from the weaning period may be more appropriate than early donor milk to meet the nutrient requirements calculated to achieve adequate growth rates among preterm infants when a mother’s own milk must be augmented with donor milk

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