I like milk. I drink it with every meal. Breakfast, lunch and dinner. Whether you can digest milk comfortably after childhood is a genetic fluke. For many people, the ability to produce lactase - the enzyme that allows the body to break down lactase, the sugar in milk - disappears after childhood, when we no longer need to survive on our mother's milk.
Lactase persistence - the gene that allows about a third of adults to drink milk without major digestive pains - tends to break down geographically, as you can see in this infographic from Nature's history of milk tolerance.
