Why the 19th century infant mortality rate was sky-high and how breast milk helped lower it


Most people probably have no idea how incredible breast milk truly is - that it can adapt to the baby's needs, that it virtually creates the baby's immune system from scratch. 

This is not widely known. 

Neither is the existence of HMOs. 

Human Milk Oligosaccharides (HMOs) are the third largest solid component in breast milk. They are a special group of milk sugars that have no nutritive function, but play a unique role in an infants’ growth. 

To reiterate: HMOs are indigestible. 

So how do they provide value and how were they even uncovered?

Interest in milk sugar started more than 100 years ago. The discovery of HMOs was driven by both scientists and physicians, each with different perspectives and interests.

Pediatricians and microbiologists were trying to understand the observed health benefits associated with human milk feeding. Chemists were trying to characterize the carbohydrates uniquely found in human milk.

By the end of the 19th century: mortality rates were as high as 20-30% in the first year of an infant’s life. 

Imagine that. 

Only seven out of every 10 babies was living to age four. 

The stress. The heartache. The tragedy. 

But it was observed that breast-fed infants had a much higher chance of survival and had lower incidences of diarrhea and other diseases than “bottle-fed” infants.

This marked a crucial discovery. 

The mortality rate was seven times higher among bottle-fed infants compared with breast-fed infants. 1

Discovery of the importance of gut bacteria for health and disease 2-4

A major breakthrough for infant survival was the discovery of microorganisms and their importance to health, and the observation that milk carbohydrates play an important role in the growth of these microorganisms.

By 1886, Theodor Escherich, an Austrian pediatrician and microbiologist, discovered a relationship between intestinal bacteria and the physiology of digestion in infants. This research led to him being recognized as the leading bacteriologist in pediatrics.

Escherich explored infants’ gut bacterial composition and the transformation of this flora from birth onwards. He pointed out the role of gut bacteria in the decomposition of foods, and the clinical implications of gut flora.

Along with the observation that infant health is linked to both breast-feeding and intestinal bacteria, Ernst Moro noted significant differences between the bacterial composition of the feces of breast-fed infants ompared with bottle-fed infants.

In 1900, Moro first isolated Lactobacillus acidophilus from infant feces. Nowadays, Lactobacillusacidophilus is one of the most commonly used probiotics for protection against the "bad" bacteria that cause disease.

In the 1950s, Paul György and Richard Kuhn started their impressive collaboration on human milk oligosaccharide research. They started to investigate the importance of human milk compared with cow's milk in infants’ resistance against infections. They found that some oligosaccharides and polysaccharides from human milk functioned as the growth factors of beneficial gut bacteria.

Chemical observation and identification of HMOs

In parallel to the observations by pediatricians and microbiologists, chemists also showed great interest after Eschbach found human milk contained a different type of sugar than cow milk.

They found that the lactose in human and bovine milk was identical, except that human milk contained another type of carbohydrate.  In the early 1930s, researchers were able to characterize this unique carbohydrate fraction and named it “gynolactose”. A few years later, Michel Polonowski and Jean Montreuil separated the first 2’- fucosyllactoses (2′-fucosyllactose and 3-fucosyllactose) from “gynolactose”. This marked the discovery of the first individual HMO. In the following years, Montreuil's group in France and Kuhn's group in Germany discovered more than a dozen individual human milk oligosaccharides.

HMOs are made up of a combination of five simple sugar “building blocks”:

  • Glucose (Glc)
  • Galactose (Gal)
  • N-acetylglucosamine (GlcNAc)
  • Fucose (Fuc)
  • Sialic acid (Sia)

By now, hundreds of different HMOs have been identified, but not every mother synthesizes the same set of oligosaccharides. Oligosaccharide amount and composition vary between women and over the course of lactation. Milk from randomly selected mothers contain as few as 23 and as many as 130 different oligosaccharides.5 

How can HMOs benefit your baby?

The prebiotic function of HMOs is the oldest known and most well-studied benefit. HMOs are not metabolized by the infant as an energy source. Instead, they pass through the stomach and the small intestine, arriving in the large intestine, where beneficial bacteria metabolize them.6 Prebiotics support the growth of good bacteria and reduce the growth of harmful bacteria and pathogens, thus improving the health of the infant’s gut microbiome. A healthy microbiome reduces the risk of dysbiosis-related diseases, such as necrotizing enterocolitis (NEC) and sepsis.

About 70 percent of the immune system resides in the gut, so it's crucial to give your baby the building blocks they need from the start. HMOs also play an essential role in the maturation of the newborn’s immune system by interacting with various immune cells in the gut and in systemic circulation, thereby regulating immune cell activity and inflammation.7

In addition, HMOs function as an inhibitor, blocking toxins and infections caused by bacteria and viruses in the gut. This is why breast-fed infants had much lower incidences of diarrhea and other infectious diseases than “bottle-fed” infants observed in the 19th century.

With a perfect blend of fats, lactose, HMOs, proteins, vitamins, minerals, and other components that support a baby's growth and development, breast milk is the gold standard for infant nutrition. As the third largest solid component in breast milk, HMOs help to set babies up for a lifetime of good nutrition and health by stimulating the immune system, promoting good gut bacteria, strengthening the gut barrier function and blocking pathogens.


  1. Montreuil, J. "The saga of human milk gynolactose." New Perspectives in Infant Nutrition, Sawaztki, G., Renner, B., Eds., Georg Thieme Verlag, Stuttgart (1993): 1-11.
  2. Kunz, Clemens. "Historical aspects of human milk oligosaccharides." Advances in Nutrition 3.3 (2012): 430S-439S. 
  3. German, J. Bruce, et al. "Human milk oligosaccharides: evolution, structures and bioselectivity as substrates for intestinal bacteria." Personalized nutrition for the diverse needs of infants and children. Vol. 62. Karger Publishers, 2008. 205-222.
  4. Bode, Lars. "Human milk oligosaccharides: every baby needs a sugar mama." Glycobiology 22.9 (2012): 1147-1162.
  5. German, J. Bruce, et al. "Human milk oligosaccharides: evolution, structures and bioselectivity as substrates for intestinal bacteria." Personalized nutrition for the diverse needs of infants and children. Vol. 62. Karger Publishers, 2008. 205-222.
  6. Moukarzel, Sara, and Lars Bode. "Human milk oligosaccharides and the preterm infant: a journey in sickness and in health." Clinics in Perinatology 44.1 (2017): 193-207.
  7. Smilowitz, Jennifer T., et al. "Breast milk oligosaccharides: structure-function relationships in the neonate." Annual review of nutrition 34 (2014): 143-169.







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