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Benefits of human milk oligosaccharides: shaping the microbiome of infants

By Chloe Autran, PhD

With approximately 200 different human milk oligosaccharides (HMOs) structures,1 these complex sugars are the third most abundant ingredient in breast milk after lactose and fat.2

HMOs are even more abundant than protein.2 But unlike protein, HMOs are not digested by babies and do not provide a direct source of energy. Instead, HMOs pass through the stomach and the small intestine unharmed and then land in the large intestine intact, where most of the beneficial bacteria live. HMOs feed these “good” bacteria and create a healthy gut environment that can crowd out potentially harmful pathogens such as viruses and bacteria.3

As different bacteria consume HMOs, they release valuable substances called short chain fatty acids that provide benefits to the cells that line the infant’s gut. One bacterium in particular, Bifidobacterium longum infantis (B infantis), prefers HMOs as its main food source. This beneficial bacterium is only found to be abundant in infants that are fed human milk. B infantis interacts directly with the cells to help strengthen the gut lining and prevent leaks in the gut that could allow bacteria and other inflammatory factors to harm the baby’s immune system. When a large spectrum of mother-made HMOs are present, a variety of beneficial bacteria are being fed. When HMOs are not present, fewer beneficial bacteria are being fed, which may lead to the overgrowth of harmful pathogens.4


  1. Moukarzel S, Bode L. Human milk oligosaccharides and the preterm infant: a journey in sickness and in health. Clin Perinatol. 2017;44(1):193-207. doi:10.1016/j.clp.2016.11.014
  2. Plaza-Díaz J, Fontana L, Gil A. Human milk oligosaccharides and immune system development. Nutrients. 2018;10:1038. doi:10.3390/nu10081038
  3. Newberg DS, He Y. Neonatal gut microbiota and human milk glycans cooperate to attenuate infection and inflammation. Clin Obstet Gynecol. 2015;58(4):814-826. doi:10.1097/GRF.0000000000000156
  4. Milani C, Duranti S, Bottacini F, et al. The first microbial colonizers of the human gut: composition, activities, and health implications of the infant gut microbiota. Microbiol Mol Biol Rev 2017