Yes, breast milk contains lactose, which is why nature equipped infants with an enzyme called lactase. Unfortunately, that enzyme becomes less active after weaning the infant from the breast, and most adults lose the ability to break down milk sugar altogether. Interestingly enough, in Northern Europe and East Africa, we have seen an adaptation to consuming dairy through what is called lactase persistence. In other words, people in those regions appear to continue producing lactase into adulthood, thus enabling them to better digest milk and other dairy products. For example, raw milk is a staple in some of the remaining hunter-gatherer tribes of East Africa (e.g., the Maasai). Those native tribes thrive on a diet of raw milk mixed with fresh blood as their primary source of nutrients.