Article - Glycoconjugates in human milk: protecting infants from disease.

Expert Review

Reviewer: Jasminka Krištić

6th Apr 2022

Conflict of interest

None

Take home message

This study looks at the role of carbohydrates in human milk and concludes that they play a health protective role in infants.
Infant formula preparations could be enhanced to include free oligosaccharides, glycoproteins and glycolipids and offer protection to babies against disease in early months of life.

Evidence category

C: Non-randomized trials, observational studies, narrative reviews

Summary review

The protective properties of human milk have been, until recently, almost exclusively attributed to maternal antibodies within the milk. Moreover, this has become widely accepted conventional wisdom. However, more recent studies have shown that carbohydrates present in human milk, either as free oligosaccharides or bound to proteins or lipids (forming glycoproteins and glycolipids, respectively), also protect infants against disease. In this paper the authors make an exhaustive review of the human milk glycoproteins and glycolipids which play protective role against infections together with their mode of action. In addition to the protective role of human milk glycoproteins and glycolipids, the authors also discuss the protective role of bovine milk glycoproteins and glycolipids, since infant formulas based on cow's milk are commonly used as a replacement for mother's milk.

Clinical practice applications

The information presented in this review has practical application for improving infant formula preparations. The findings reviewed in this paper together with future research in this area could lead to the development of enhanced infant formulas, enriched with recombinant human milk glycoproteins and glycolipids which would provide better protection for babies against many diseases.

Considerations for future research

It is well known that glycans (complex sugars that are often attached to proteins and lipids) have numerous roles in various physiological processes. The ability of glycans to inhibit binding of different pathogens to host cell ligands, as it was shown for glycans present in human milk, represent just one more example of important roles played by glycans. Further research is needed to understand the mechanisms by which milk glycans ensure protection against different pathogens.

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Abstract

Breastfeeding is known to have many health benefits for a newborn. Not only does human milk provide an excellent source of nutrition, it also contains components that protect against infection from a wide range of pathogens. Some of the protective properties of human milk can be attributed to the immunoglobulins. Yet, there is another level of defense provided by the "sweet" protective agents that human milk contains, including free oligosaccharides, glycoproteins and glycolipids. Sugar epitopes in human milk are similar to the glycan receptors that serve as pathogen adhesion sites in the human gastrointestinal tract and other epithelial cell surfaces; hence, the milk glycans can competitively bind to and remove the disease-causing microorganisms before they cause infection. The protective value of free oligosaccharides in human milk has been well researched and documented. Human milk glycoconjugates have received less attention but appear to play an equally important role. Here, we bring together the breadth of research that has focused on the protective mechanisms of human milk glycoconjugates, with a particular focus on the glycan moieties that may play a role in disease prevention. In addition, human milk glycoconjugates are compared with bovine milk glycoconjugates in terms of their health benefits for the human infant.