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Recently, I had the pleasure of talking to Dr. Wesley Zandberg, Assistant Professor at the University of British Columbia, who completed his PhD and post-doctorate work at Simon Fraser University. While working on projects aimed at developing inhibitors for the enzymes that break down complex carbohydrates, Wesley was introduced to the challenges associated with analyzing the surprisingly complex range of carbohydrates found in nature. Students in the Zandberg lab are now focused on developing improved analytical methods for glycobiology.

In the first part of our chat, we discussed prebiotics in milk and milk products and the importance of understanding human milk oligosaccharides (HMOs). Read on for a summary of the topics we covered.

What are human milk oligosaccharides (HMOs) and why are they important to us?

Human milk is often considered the “gold standard” of nutrition for newborns during the first few months of their lives. In addition to containing all the nutrients that are vital for growth and development, human milk contains ingredients that might provide health benefits that no other traditional nutrients can provide. These functional ingredients include HMOs.² HMOs comprise a group of structurally complex glycans that are highly abundant in human milk.³ In fact, only trace amounts of such oligosaccharides can be found in bovine milk, while the concentration is 10 times higher in human milk.

Milk—from all mammals—is a very rich source of carbohydrates. The major carbohydrate found in milk is the sugar lactose. Lactose is self-composed of glucose and galactose, which are chemically linked by a single chemical bond. Provided that they have the lactase enzyme in their small intestine, newborns (and most adults) can break down lactose into these simpler pieces that can then serve as a calorie source. While milk oligosaccharides are found in all species of mammals, the richest source is HMOs in humans.

However, humans—even babies—are unable to break down these oligosaccharides on their own, meaning we cannot digest them. We rely on the microorganisms living in our large intestine and colon to break them down into simpler carbohydrates that can then be absorbed, or more likely metabolized by the bacteria in babies’ guts. The beneficial effects of HMOs include promoting the growth of Bifidobacterium bifidum, which is a bacterial species found in the human body that helps prevent infection and provides vitamins to our bodies.²

What are the main functions of HMOs?

In the 1930s, when these intriguing molecules were first characterized, their functions were unknown. Scientists are increasingly realizing the importance of HMOs and the effects they have on not only the gut, but also the body and brain.⁴ HMOs have three main functions for humans: they create a prebiotic effect, an anti-adhesive effect, and an immune effect.

The prebiotic effect

Human bodies ideally choose the growth of “good”’ bacteria over bacteria that cause diseases. However, when babies are born, their immune systems are untouched, and their bodies need to be trained to recognize these beneficial bacteria.²

A mixture of HMOs promotes the growth of a group of bacteria, including Bifidobacteria which helps babies gut health. However, about 90% of all HMOs are found intact and unmetabolized in infant feces.² This suggests that HMOs have effects other than just serving as prebiotic “fuel” to establish and maintain a certain desired microbiota composition, which brings us to the next function.²

The anti-adhesive effect

The mucus we see in the lining of the large intestine and colon is protecting the layer of cells that keeps microorganisms away from our immune system. If the microorganisms living in our gut interact with the immune system, problems can occur. Pathogenic bacteria and viruses are capable of recognizing these complex carbohydrates that make up the mucus lining in the gut. The first step required to initiate infection of a baby or any human is when bacteria stick to the mucus.

The role of HMOs, which chemically resemble the mucus lining of the gut, is to prevent pathogens from adhering to the gut lining and establishing an infection. You can think of HMOs as a nonstick coating in your intestines that draws attention away from the gut lining, blocking pathogen adhesion to protect infants against infections.²

The immune effect

Recently, it’s been discovered that oligosaccharides are absorbed through the gut into the bloodstream of babies and transported throughout the body. It is clear that some of these oligosaccharides are directly interacting with immune cells. This has the effect of dampening inflammation, which is a good thing. The neo-natal diet is effectively starting to train the immune system.

Learn more

So, now that you know more about HMOs and their functions, stay tuned for part 2, where we discuss how many HMOs there could be, and what their future looks like.

References

• Collins, J. Prebiotics. WebMD. https://www.webmd.com/digestive-disorders/prebiotics-overview
• Bode, L. Human milk oligosaccharides: prebiotics and beyond. Rev. 2009, 67, S183–S191. https://doi.org/10.1111/j.1753-4887.2009.00239.x
• Triantis, V.; Bode, L.; van Neerven, R. J. J. Immunological effects of human milk oligosaccharides. Pediatr. 2018, 6. https://doi.org/10.3389/fped.2018.00190
• Qatar Environment & Energy Research Institute; Abbott. One of the most important ingredients in breast milk you’ve never heard of. Nature Portfolio. https://www.nature.com/articles/d42473-018-00007-1

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