Human milk oligosaccharides (HMO) and IBS

Copy of Human Milk Oligosaccharides

Jimmy Lee - Research Dietitian, 15 December 2022

IBS is always an exciting and growing area of research in not just the dietetics world, but also the wider healthcare sector. In this blog, let’s look at the effectiveness of a potential treatment option - human milk oligosaccharide (HMO).

First things first, what is HMO?

As the name suggests, HMO is a type of sugar (oligosaccharides) found in human breast milk. It is the third most abundant solid component in human milk, followed by fats and lactose (1).

HMOs are minimally digested in the stomach or small intestine. They reach the colon undigested and are fermented by gut bacteria, hence their prebiotic characteristics (2). Did you know that approximately 200 types of structurally different HMOs have so far been identified in human milk (3,4)? Although 2′-Fucosyllactose (2′-FL) is the most abundant type of HMO found in women (5), HMO composition varies between women and can depend on stages of lactation.

How may HMOs be beneficial?

From an infant gut health perspective, HMOs may contribute to building a stronger gut for the baby, by acting as nutrients for the growth of ‘good’ bacteria in their gut (2,6). HMOs may also help build a healthier immune system for the baby (2).

In recent years, some infant formulas are also fortified with HMOs. HMO prebiotic supplements for adults have also recently begun emerging into the health products market.

How may it help IBS?

One of the proposed causes of IBS is the imbalance of the gut bacteria environment, also known as ‘gut dysbiosis’. Given the prebiotic characteristic of HMO, it is suggested that HMOs may help regulate the ratio of ‘good’ and ‘bad’ bacteria in the gut, and strengthen the immune system to protect against harmful bacteria or viruses (7).

One of the theories is that supplementing HMO in addition to an IBS patient’s usual diet may increase Bifidobacteria, a type of gut-friendly bacteria that is often decreased in this population (8). An earlier study indicated that supplementing 20g of HMO per day resulted in an increase of bifidobacteria in healthy adults, and this dosage was well tolerated (9). However, the effects on IBS patients remain unclear until recent years.

What evidence is available for now?

Evidence regarding the use of HMO, especially in the adult IBS population, is still in its early stages. Notably, there are two clinical trials in recent years that explored the effects of HMO in IBS patients. We have summarised the study characteristics and findings in the table below.

Blog tables template

Do you recommend it?

Given the limited and low-quality evidence available, it is currently difficult to recommend a dosage and duration of treatment for IBS patients at this stage. Furthermore, current clinical guidelines make no recommendation of using HMO to treat IBS.

Further studies with a larger number of well-defined participants (and maybe targeting a specific IBS subgroup), longer follow-up time, a comparison with healthy controls and adequate FODMAP dietary intake data may provide more insight regarding the effectiveness of HMO in this population. Until now, let’s sit back, relax and look out for more updated evidence in this exciting area of gastrointestinal research.


  1. Seferovic MD, Mohammad M, Pace RM, Engevik M, Versalovic J, Bode L, et al. Maternal diet alters human milk oligosaccharide composition with implications for the milk metagenome. Scientific Reports. 2020;10(1).
  2. Walsh C, Lane JA, van Sinderen D, Hickey RM. Human milk oligosaccharides: Shaping the infant gut microbiota and supporting health. Journal of Functional Foods. 2020;72:104074.
  3. Wang J, Chen M-S, Wang R-S, Hu J-Q, Liu S, Wang Y-Y-F, et al. Current advances in structure–function relationships and dose-dependent effects of human milk oligosaccharides. Journal of Agricultural and Food Chemistry. 2022;70(21):6328–53.
  4. Vandenplas Y, Berger B, Carnielli V, Ksiazyk J, Lagström H, Sanchez Luna M, et al. Human milk oligosaccharides: 2′-fucosyllactose (2′-FL) and lacto-N-Neotetraose (LNNT) in infant formula. Nutrients. 2018;10(9):1161.
  5. Ferreira AL, Alves R, Figueiredo A, Alves-Santos N, Freitas-Costa N, Batalha M, et al. Human milk oligosaccharide profile variation throughout postpartum in healthy women in a Brazilian cohort. Nutrients. 2020;12(3):790.
  6. Vandenplas Y, Berger B, Carnielli V, Ksiazyk J, Lagström H, Sanchez Luna M, et al. Human Milk Oligosaccharides: 2′-Fucosyllactose (2′-FL) and Lacto-N-Neotetraose (LNnT) in Infant Formula. Nutrients. 2018 Aug 24;10(9):1161.
  7. Palsson OS, Peery A, Seitzberg D, Amundsen ID, McConnell B, Simrén M. Human milk oligosaccharides support normal bowel function and improve symptoms of irritable bowel syndrome: A Multicenter, open-label trial. Clinical and Translational Gastroenterology. 2020;11(12).
  8. Iribarren C, Törnblom H, Aziz I, Magnusson MK, Sundin J, Vigsnæs LK, et al. Human milk oligosaccharide supplementation in irritable bowel syndrome patients: A parallel, randomized, double‐blind, placebo‐controlled study. Neurogastroenterology & Motility. 2020;32(10).
  9. Elison E, Vigsnaes LK, Rindom Krogsgaard L, Rasmussen J, Sørensen N, McConnell B, et al. Oral supplementation of healthy adults with 2′-O-fucosyllactose and lacto-N-neotetraose is well tolerated and shifts the intestinal microbiota. British Journal of Nutrition. Cambridge University Press; 2016;116(8):1356–68.
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