LLLI Center for Breastfeeding Information

Journal Abstract of the Month for January 2004

"Nutritional and physiologic significance of human milk proteins"

Author: Bo Lonnerdal

Am J Clin Nutr 2003;77(suppl):1537S-43S

Breast milk proteins assist in providing adequate nutrition to breastfed infants while simultaneously aiding in the defense against infection and facilitating optimal development of important physiologic functions in newborns.

Proteins with antimicrobial activity (immunoglobulins, k-casein, lysozyme, lactoferrin, haptocorrin, a-lactalbumin and lactoperoxidase) are resistant to proteolysis in the GI tract and may contribute to the defense of breastfed infants against pathogenic bacteria and viruses. Milk proteins also promote the growth of beneficial bacteria such as Lactobacilli and Bifidobacteria, as it alters intestinal pH. Other proteins/hormones (insulin-like growth factor, epidermal growth factor and lactoferrin) assist in the maturation of the infant gut. It is also possible that the effectiveness of lactoferrin in this process occurs only when present in breast milk. When added to infant formula, other constituents of the artificial product can interfere with iron utilization from lactoferrin in the infant. However, when lactoferrin is added to the formula of other species, there is a weight gain (possibly due to the enhancement of cell proliferation).

The mother's immunity to general pathogens is transferred to her breastfed infant by sIgA, mediated by the enteromammary system. In this way the baby's immature immune system can be supplemented by the mother's acquired immunities.

Lysozyme is a major component of the whey fraction in human milk. In recent studies, lysozyme is being considered as a natural antibiotic in chicken feed, with the possibility of replacing antibiotic drugs now used.

There are several types of cytokines released from cells in human milk which are immunomodulatory, but which also are inflammatory, lessening the effect of infections.

This paper is being categorized with the following keywords: Human Milk-Immune Factors, HM-Proteins, HM-Composition, HM-Hormones, Yeast, Cytokines, HM as Medicine, Physiology, Pre/Probiotics, Gut, HM-Enzymes, Lactoferrin, HM-Vitamins B-12, Casein