Prebiotics in Breast Milk: How Do They Work?

Typically, people consider prebiotics to be soluble fiber compounds that, once ingested, can’t be digested in their passage through the upper gastrointestinal tract. Subsequently, when the prebiotics reach the large intestine, the bacteria that live there and can process this fiber, use it as an energy source. As a result, prebiotics in breast milk stimulate the growth of colonic bacteria populations.

Prebiotics are often confused with probiotics

As their names suggest, prebiotics and probiotics are related. However, it’s important to understand their differences. By definition, probiotics are live microorganisms that positively affect health. Some of them are lactobacilli and bifidobacteria (both belong to the lactic acid bacteria group) and saccharomyces (a genus of fungi).

Furthermore, prebiotics aren’t bacteria. They’re compounds that provide the food source that allow probiotics to live and proliferate in their niche, the colon. Prebiotics are substances that act as food for probiotics.

Why are the bacteria that live in your gut important?

First, they’re very numerous. Bacteria make up most of the gut flora. They represent over half of the dry mass of feces.

On the other hand, their composition is very variable. Gut microbiota is made up of more than a thousand species. Nevertheless, experts recognize that there’s a numerical predominance of about 30 or 40 species in each person.

Their importance lies in the fact that a huge number of microorganisms make up an extraordinarily mature ecosystem that’s resistant to exterior changes. “Intestinal homeostasis” is the medical term for this balance.

Exposure to antibiotics, enteric infections, or dietary changes may alter this homeostasis. Scientific evidence links the imbalance of intestinal microbiota with a long list of diseases. To restore this balance, the patient may ingest prebiotics and probiotics and, in severe cases, may require a fecal microbiota transplant (FMT).

Breast milk is rich in prebiotics and probiotics

Currently, science recognizes that breast milk is an irreplaceable factor of initiation, development, and composition of a baby’s gut microbiota.

Nowadays, not many people know that breast milk contains a large number of lactic acid bacteria that the mother provides her baby to start intestinal colonization. It’s estimated that babies ingest about 800 milliliters of breast milk a day and receive between 100,000 and 10 million bacteria a day.

On top of that, the mammary glands produce a unique repertoire of prebiotic compounds: oligosaccharides. The combined intake of probiotics and prebiotics helps ensure that “good bacteria” colonize the baby’s intestines.

The carbohydrates of milk can be constituted by a single sugar molecule: monosaccharides. For example, glucose, galactose, and fructose. Oligosaccharides are composed of five types of monosaccharides, which randomly combine to form linear or branching structures.

Surprising data of prebiotics in breast milk

The proliferative effect that breast milk exerts on lactic acid bacteria isn’t related to a single substance, but due to various factors. In particular, the prebiotic effect of breast milk has been attributed to the low protein and phosphate concentration and the presence of lactoferrin, lactose, nucleotides, and oligosaccharides.

Experts still don’t know the actual prebiotic role of each of these substances, with the exception of oligosaccharides, the most studied of the group.

Nevertheless, experts don’t know the meaning behind the fact that the huge repertoire of oligosaccharides varies from one woman to another and, in the same woman, from one lactation stage to another.

In this regard, they estimate that the approximate number of oligosaccharides can vary from about 150 compounds to hundreds of thousands. Within this universe, experts also know that there’s a predominance of the series of galactooligosaccharides (GOS).

Additional functions that provide the oligosaccharides of breast milk

The repertoire of oligosaccharides in breast milk is inimitable. Several studies have shown that these compounds, in addition to being “food for bacteria,” may perform other functions:

• They can deceive viruses and pathogenic bacteria. Some variants mimic oligosaccharides of the intestinal wall, precisely those that use pathogens to invade healthy cells. When the pathogen falls for it, infection is prevented.
• Also, they may regulate the activation of immune cells.