Carbohydrates in Human Milk

Nutritionally, there are three monosaccharides that make up all carbohydrates: glucose, fructose, and galactose. When glucose and galactose join together, they create lactose. Lactose is the main carbohydrate present in human milk, providing ~8.5 calories per ounce of human milk. Average lactose concentrations:

• are stable over the first 6 months of lactation

• decrease slightly from 6 months-1 year and then remain stable over the second year of lactation

• are higher if the infant is feeding frequently and lower if it has been a while since the infant has fed

Lactose is an interesting disaccharide, because infants are able to digest it due to the release of an enzyme called lactase. Lactase breaks the bond between glucose and galactose, both of which can be absorbed into the body. From birth, infants with galactosemia cannot consume lactose – not from breast milk or standard infant formula. Galactosemia is an inability to produce energy from galactose, and so levels in the blood rise. This can have severe consequences, including failure to thrive and death if not diagnosed.

Human milk oligosaccharides (HMOs) are also carbohydrates, but they do not provide any caloric value to the infant. HMOs serve as a food source for beneficial bacteria and can also have a direct impact on the infant’s immune response. 

From what we know about HMOs:

• there are over 200 structures

• mothers secrete a consistent profile of HMOs

• different mothers secrete different types of HMOs

Human milk oligosaccharides can also be protective of viral and bacterial causes of diarrhea – depending on secretor status and Lewis antigen status of the HMOs produced.

Glycoconjugates are carbohydrates bound to protein or lipid molecules. These molecules are important for the infants innate immune response. A well known example of a glycoconjugate is lactoferrin – a molecule that serves as a bacteriocide and fungicide by hydrolyzing their RNA. Lactoferrin also serves as a stimulant to small intestine maturation in the newborn. Interestingly, lactoferrin has also been implicated in bone health in postmenopausal women, and more recent research is looking at the impact of lactoferrin on healthy infants.

The more I learn, the more I am convinced: human milk is magic.

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