In addition to supporting infant nutrition and development, human lactation and breastfeeding have evolved to protect infants against infectious diseases (ID): breastfed infants have dramatically lower ID risk than infants fed milk substitutes.
The activity of the immune system of milk (ISOM) likely plays an important role in this protection. The ISOM includes leukocytes, antibodies, cytokines, and antimicrobial proteins that likely play important roles against infectious diseases and the immune system development.
Mother’s milk contains everything needed to mount immune responses, including antibodies and multiple types of cells. To test the impact of milk’s immune system on infant health, researchers performed a study among breastfeeding mother-infant dyads in Kilimanjaro, Tanzania, a rural area of East Africa where breastfeeding is the norm in the population.
Protection Against Infectious Diseases
For the study, the team combined a few milliliters of milk with a small amount of bacteria, then placed the mixture in an incubator overnight. They then measured the increase of interleukin-6, which is a proinflammatory molecule. The in vitro response gives an indication of how the ISOM is likely to respond to bacteria encountered in the infant’s body.
The infants were followed-up to assess if those who received milk that mounted stronger immune responses during the in vitro testing were at lower risk for infectious diseases.
The team found that infants in the group that received milk that mounted stronger immune responses had a decreased risk for respiratory infections. But in the case of gastrointestinal infections this same group had a higher risk.
The researchers believe that their results may indicate that inappropriate responses by milk’s immune system, like bacteria normally present in the gut, can be disruptive. Also, in addition to reducing the risk for respiratory diseases, the ISOM may help train the infant’s developing immune system to respond to dangerous bacteria.
Katherine Wander, et al. Tradeoffs in milk immunity affect infant infectious disease risk, Evolution, Medicine, and Public Health, Volume 10, Issue 1, 2022, Pages 295–304, https://doi.org/10.1093/emph/eoac020
EurekAlert! (2022, Jul 12). Milk boost: Research shows how breastfeeding offers immune benefits. Binghamton University Peer-Reviewed Publication. EurekAlert! Retrieved from:
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