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Published on: December 16, 2015
Composition of premature breast-milk during lactation: constant digestible protein content (as in full term milk)
R J Beijers1, F V Graaf, A Schaafsma
1Bosch Medicentrum, Department of Paediatrics, Hertogenbosch, Netherlands.
Insights
Preterm infant breast milk contains significant undigestible proteins, impacting nutrient absorption. Only 30-60% of total protein is available for body protein synthesis, though digestible protein remains stable.
Area of Science:
- Neonatal nutrition
- Human milk composition
- Infant physiology
Background:
- Determining protein requirements for preterm infants is crucial.
- Human milk protein content is a key factor in infant nutrition.
- Understanding the bioavailability of protein in preterm breast milk is essential.
Purpose of the Study:
- To analyze the protein content and composition of preterm breast milk.
- To quantify the proportion of digestible and undigestible proteins.
- To assess protein availability for body protein synthesis in preterm infants.
Main Methods:
- Analysis of 24-hour milk expressions.
- Utilized Kjedahl method for total nitrogen.
- Employed GPC, SDS-PAGGE, and nephelometric detection for protein and sIgA analysis.
Main Results:
- Premature breast milk colostrum contains up to 70% undigestible proteins.
- This proportion decreases to 20-40% in transitional and mature preterm milk.
- The non-protein nitrogen (NPN) fraction ranges from 18% to 26%, with 30-60% of total protein available for synthesis.
Conclusions:
- A significant portion of preterm breast milk protein is not readily available for infant growth.
- Digestible protein amounts remain relatively stable throughout lactation.
- Further research into optimizing protein utilization in preterm infants is warranted.
Abstract:
There is much discussion about the protein requirements of (very) preterm infants. The protein content of breast milk plays an important role in this discussion. For this reason, we took a close look at the protein content and its composition in premature breast milk. Complete 24 h expressions-were examined using the Kjedahl method, GPC, SDS-PAGGE and nephelometric detection of sIgA. Colostrum of premature breast milk contains a large amount of undigestible proteins, up to 70% of true protein, which decreases to 20-40% in transitory and mature preterm milk. The NPN fraction of mature preterm breast milk was, dependent on the degree of prematurity 20-25%; increasing during lactation from about 18% to 22-26%. This means that, depending on the lactation period only 30-60% of the total protein content of breast milk is available for body protein synthesis. In absolute amounts, digestible protein is reasonably stable during lactation.
