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name of the term : HMO

Short introduction

  • Breast milk not only provides nutrients for the infant’s healthy growth and development but also numerous bioactive substances, which are mainly human milk oligosaccharides (HMOs).
  • HMOs represent the third largest solid component of breast milk after lactose and fat.
  • So far, more than 150 different HMOs have been identified.
  • Human milk oligosaccharides (HMOs) are a complex mixture of indigestible carbohydrates with a high degree of structural diversity.
  • HMOs can be roughly classified into three different types; fucosylated HMO, sialylated HMO and core HMO.
  • Although types and concentrations of HMOs vary considerably among lactating women and over time, 2′-O-fucosyllactose (2′-FL) and lacto-N-neotetraose (LNnT) are commonly found in abundance in human milk.
  • The most abundant HMO is 2′-FL, a fucosylated HMO, which constitutes nearly 30% of the total HMOs among secretor mothers. LNnT is one of the more abundant core structures.
  • Levels of both 2’-FL and LNnTvary among women depending on stage of lactation, geographical origin and genetics.
  • Technology advancements have made it possible to supplement infant formulas with HMOs. The addition of HMOs is a step forward in creating infant formulas. 
  • Amongst the synthesised HMOs, 2′-O-fucosyllactose (2′-FL) and lacto-N-neotetraose (LNnT) are widely studied and are considered safe for infant nutrition.
  • In 2015, the European Food Safety Authority (EFSA) concluded that two important HMOs (2’-FL and LNnT) are safe to include in infant formula.

Main natural sources

  • The only natural source of HMOs is human milk (breast milk).

Main function

  • Several studies have documented the beneficial effects of HMOs, including modification of the intestinal microbiota, anti-adhesive antimicrobial effects, modulation of intestinal epithelial cell response and effects on immune and brain development.

Mechanism of action

  • In the gastrointestinal tract, HMOs resist hydrolysis (breakdown) by enzymes and absorption. HMOs enter into the large intestine (colon).
  •  In the colon, bifidobacteria and lactobacilli, the good bacterial residents, degrade HMOs through fermentation. They use HMOs for their own growth.
  • During this fermentation process, short chain fatty acids (SCFAs) are formed.
    • SCFAs lower the colonic pH (more acidic environment), which inhibits growth and survival of pathogens (harmful invaders) and, consequently, promotes growth of beneficial bacteria (bifidobacteria and lactobacilli).
    • SCFAs: acetate, propionate, butyrate – each with unique effects. Butyrate is beneficial for colonic health. It is a source of energy for the colon epithelial cells (cells that line the colon). Butyrate makes the epithelial gut barrier less permeable through increased mucus production and so strengthens its role in disease prevention. Butyrate also promotes normal cell differentiation (specialisation of cells) and proliferation (multiplying).
    • Lactate and acetate from bacterial production form a chemical barrier against potential pathogens.
    • SCFAs help regulate sodium and water absorption; they can enhance absorption of calcium and other minerals.
  • Stimulated growth of bifidobacteria and lactobacilli prevents binding of pathogens to the epithelial cell surface. The more space and nutrients taken by the good bacteria, the less space and nutrients for the bad ones.
  • Growth of the beneficial bacterial leads to an increased bacterial biomass resulting in an increase in volume and softness of the faeces. HMOs increase the bacterial mass and the osmotic water-binding capacity in the gut lumen. These actions increase stool weight and frequency; they also soften the stool, which indirectly contributes to decreased transit time.
  • When infants are fed with a formula supplemented with 2-FL and LNnT, they develop a distinctive bacterial stool profile that is more consistent with breastfed infants than infants fed with a formula that is not supplemented with prebiotics.
  • Studies demonstrate that  HMOs directly and indirectly affect the infant’s mucosal and systemic immunity through their actions on the gut.
  • Beneficial effects on brain development: studies have also demonstrated that HMOs (such as 2’-FL) may enhance memory and learning.
Synonyms : Human milk oligosaccharides

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