What is the difference between lactose in breast milk, donkey milk and lactose in artificial formulas?

Lactose is one of the most important carbohydrates in breast milk. Manufacturers of artificial formulas voluntarily add lactose into their formulas. However sometimes bottle-fed babies have to switch to lactose-free formulas, as their bodies are unable to process this type of lactose.

So what happens in the body? Is lactose friend or foe?

It turns out that the lactose in breast milk and in the formula are two different isomers of lactose (they are formed from the same molecules but have a different spatial conformation).

The main source of carbohydrates in breast milk is beta-lactose (β-lactose). Lactose makes up 80-90% of all sugars in breast milk and provides up to 40% of a baby’s energy needs. The lactose in donkey milk, as well as in women’s milk, consists of beta-lactose and in almost the same quantities.

Cow’s milk and, consequently, blends instead contain alpha-lactose (α-lactose).

Unlike α-lactose, β-lactose in breast milk is absorbed more slowly in the small intestine and is broken down and absorbed in the lower parts of the small intestine, while α-lactose is in the upper part, this difference involves the different physiological response.

Hydrolysis of β-lactose in the small intestine leads to the formation of glucose and galactose. Galactose is an integral part of galactolipids, essential for the development of the central nervous system (CNS). In addition, galactose is part of the cellular receptors containing galactosyl responsible for the work of intracellular enzymes. Galactose is also a substrate for intestinal lactic bacteria.