130 Reasons To Use Human Milk Oligosaccharides

Many nutritionists are not yet aware that human milk contains many other carbohydrates in addition to lactose. If you have never heard of lacto-n-tetraose or sialyl-lactose, you are not alone. The importance of oligosaccharides in other industries has attracted worldwide interest, but little is known about the human milk oligosaccharides.

High IQ

More than 130 different oligosaccharides in breast milk are very important for infants’ brain development and the body’s ability to resist infections. (Only two oligosaccharides have been added to baby formula to date.) The presence of oligosaccharides in breast milk may be one reason that breastfed babies later show higher IQ and are less prone to infectious diseases than formula-fed babies.

Of the substances dissolved in human milk, oligosaccharides are the third most abundant, after lactose and fat. Mature milk contains more than 15 grams of oligosaccharides per liter, while it has almost half as much protein at 9 grams per liter. Interestingly, the specific oligosaccharide set varies with the length of lactation, time of day, and maternal genotype. The oligosaccharide set can vary significantly from mother to mother. It can be different even for the same mother feeding the same baby at different breastfeeding periods, but it will always be much richer than in any formula. Oligosaccharides are some of the most flexible components of breast milk, adjusting to the baby’s needs. In marsupials and some mammals, milk also contains oligosaccharides, but cow’s milk and baby formula contain negligible amounts of them. Human milk is unique in its oligosaccharide content. It is noteworthy that the British Journal of Nutrition, in 1999, published an article stating that the composition of elephant milk is very similar to that of human milk. Perhaps the large amount of oligosaccharides in elephant milk is the secret that elephants never forget anything.

Formation of neural connections and memory

For the past two decades, oligosaccharides have been studied by mass spectrometry and NMR spectroscopy. The great variety of oligosaccharides is achieved by various combinations of glucose, galactose, sialic acid, fucose, and amino acids. Due to the large number of diverse connections between these components, about 130 different oligosaccharides are currently identified and the search for new ones is ongoing. Almost all of them have a lactose part at the nonreducing end of the chain and fucose or sialic acid (if present) at the reducing end of the chain.

The presence of large amounts of sialylated oligosaccharides in breast milk is noteworthy. Sialic acids, which are sugars with a nine-atom carbon chain, are important structural and functional components of the ganglia of the brain. They are believed to play an important role in the formation of nerve connections, memory formation and information transfer between cells. An experiment was conducted in which newborn rat cubs were additionally injected with sialic acid. This significantly improved learning ability, led to rapid weight gain, both in the case of sufficient nutrition and for malnourished cubs, and, moreover, the high level of mental development of rats was maintained even in adulthood. Human milk contains enormous amounts of sialylated oligosaccharides, the analogues of which are not found in cow’s milk and infant formula. An immature child’s liver is not able to synthesize enough sialic acid, so necessary during the period of intensive brain growth, namely in the first year of life.

Sialic acid

Due to the popularization of breastfeeding, additional opportunities for sialic acid research have recently become available. Previously, sialic acid research was done by analyzing serum and brain tissue. However, saliva was also found to be a source of sialic acid. Because of this, there is now a method for noninvasive testing of infants. The high concentration of sialic acid in saliva and on mucous membranes provides low adhesiveness, viscosity and therefore protective functions. According to a recent study, the saliva of breastfed infants contains 50% more sialic acid compared to that of formula-fed infants.

Source of energy

One of the most important aspects concerning human milk oligosaccharides is their ability to be digested and absorbed in the small intestine, providing the body with energy and important substances such as galactose, fucose and sialic acid. The mucosa of the small intestine of marsupials has several enzymes that break down oligosaccharides into their component monosaccharides. Recent studies have shown that in breastfed children, oligosaccharides are resistant to digestion in the small intestine and undergo fermentation only in the large intestine. Curiously, oligosaccharides do not cause intestinal fermentation and do not irritate the intestinal wall, having absolutely no effect on stool consistency, although these signs are usually attributed to undissolved substances, i.e., not absorbed oligosaccharides.

Thus, by resisting digestion in the small intestine, oligosaccharides become a major source of energy for the flora of the large intestine. Oligosaccharides have been found to contain N-acetylglucosamine (or “bifido-factor”), essential for the growth of Bifidobacterium bifidum in the large intestine. Oligosaccharides are involved in the biosynthesis of muramic acid, which is a component of the shell of bacterial cells. By the end of the first week of life, bifidobacteria account for 95% of the total bacterial population in the feces of exclusively breastfed infants, whereas their population in infants who are formula-fed is less than 70%. By producing lactic acid, bifidobacteria lower the pH of the gut. The acid in a suitable environment suppresses the multiplication of many pathogens, such as Shigella species, Escherischia bacilli, fecal Streptococcus and Clostridium, which become dominant in the digestive system of children after weaning. Short-chain fatty acids, such as acetic, propionic and butyric acids produced by fermentation, are absorbed through the walls of the large intestine, providing nutrition for the colonocytes and a source of energy for the body. Through this mechanism, about 70% of the energy of carbohydrates can be saved. Thus, most of the energy of human milk oligosaccharides can eventually be available to the infant.

Human milk oligosaccharides are not digested in the small intestine. How then can molecules such as sialic acid support brain growth? In an oligosaccharide molecule, sialic acid always occupies an extreme position, and bonds can be cleaved even if the rest of the chain is undigestible. The cleavage of sialic acids, possible due to sialidase activity in some species, is most active during absorption and is directly related to the sialic acid content of milk.

Reduction of urinary tract infections

It is assumed that the smallest oligosaccharides of human milk can penetrate the erythrocyte membrane. In marsupial cubs, this process occurs through pinocytosis. Very few oligosaccharides are excreted unchanged in the urine and feces of infants. Breastfed premature infants have been shown to contain about 1% of the daily allowance of oligosaccharides in the urine, compared to artificially-fed infants, who have negligible amounts of this substance. This proves once again that despite the peculiarities of the absorption mechanism of oligosaccharides, their digestibility is very good. The presence of certain oligosaccharides in the urinary system helps to reduce the spread of urinary tract infections.

Antibacterial role

There is increasing evidence that oligosaccharides play an important antibacterial role in the intestinal, respiratory and urinary tracts. There is a list of pathogens that certain human milk oligosaccharides resist. New research is constantly adding to this list.  Oligosaccharides prevent bacterial cells from fusing with the epithelium (infection). They act as “bait” because they are a structural analog of the host cell. These mechanisms can be realized only if the oligosaccharides reach the various organs (small intestine, intestines, respiratory tract, urogenital system, etc.) in an undamaged state. Thus, the resistance of oligosaccharides to digestion in the small intestine is essential for their function.

The first weeks of life

The presence of enormous amounts of oligosaccharides in human milk is having an impact on the development of breast milk substitutes, especially for premature infants. Thanks to advances in infertility control and modern life-support techniques, the number of premature babies is increasing rapidly. Premature babies are more susceptible to infections and various cognitive impairments than babies born at term. Brain growth peaks at 26 weeks of gestation and continues apace in the first weeks of life. Premature infants who were exclusively breastfed in the first month of life show significantly higher levels of speech proficiency (children who reached 7-8 years of age were studied) than those who were artificially fed from infancy. We hypothesize that sialylated oligosaccharides from human milk are a contributing factor.

Studies show that the milk of a woman who gives birth to a premature baby contains at least the same amount of oligosaccharides as the milk of a woman who gives birth at term. Moreover, preliminary evidence suggests that the concentration of sialylated oligosaccharides may even be higher in the milk of mothers of premature infants, which is why children, especially premature infants, should receive breast milk. Oligosaccharides should be a focus of attention for those developing infant nutrition and producing artificial formulas. The number of oligosaccharides, their complexity, and the variety of their compounds are now additional 130 reasons to breastfeed your baby.

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