Chunlin, Don't Drink My Milk

Apparently the ability to drink milk as an adult is almost exclusively a northern European trait:

Somewhat less than 40% of people in the world retain the ability to digest lactose after childhood. The numbers are often given as close to 0% of Native Americans, 5% of Asians, 25% of African and Caribbean peoples, 50% of Mediterranean peoples and 90% of northern Europeans. Sweden has one of the world's highest percentages of lactase tolerant people.

Being able to digest milk is so strange that scientists say we shouldn't really call lactose intolerance a disease, because that presumes it's abnormal. Instead, they call it lactase persistence, indicating what's really weird is the ability to continue to drink milk.

In years past, I've stopped drinking milk and eating yogurt for months at a time to see if I notice any changes, but I didn't. So I still eat and drink dairy products daily.

In normal humans, the enzyme that [digests lactose] stops being produced when the person is between two and five years old. The undigested sugars end up in the colon, where they begin to ferment, producing gas that can cause cramping, bloating, nausea, flatulence and diarrhea.

So, um. . . be careful what you drink!