Those human cultures that relied on dairy as an important source of nutrition created a survival pressure on its members. A nearly opposite ratio of lactase nonpersistence exists in people of northern European descent, who can digest dairy throughout adulthood. Many East Asians and Native Americans, up to 90 percent in some ethnic groups, become lactose-intolerant after the early childhood years as their genes direct a slowdown in the production of lactase. If the lactose isn’t reduced for absorption, it remains in the intestines, pulling in water from the rest of the body (hello, diarrhea) and being converted by our intestinal bacteria into unpleasant stuff, including lots of hydrogen gas. This reduction is known as lactase nonpersistence. But some of us will experience a drastic decrease in the amount of this enzyme, often around age 5.

Most human children feature lactase in their intestines, which allows them during their breastfeeding years to digest milk produced by their moms. Unless you don’t have enough of this enzyme, that is. Lactase enzymes in your small intestines break down countless lactose molecules into glucose and galactose, which are small enough to be absorbed by your gut lining.

A particular enzyme will perform a specific function, like joining two molecules or splitting one apart. It’s composed of two simpler sugars linked together.Įnzymes are proteins that behave like chemical factory workers in your body and are typically named with the suffix -ase. Lactose is a sugar found in mammalian milk - the milk of cows, humans, even East Asians. You could digest milk as a kid, so what happened to you? Why did you lose such a useful biological power? It’s been several hours since you enjoyed that delicious milkshake, and now your belly protests with rumbling, cramping - probable harbingers of flatulence and watery diarrhea quickly heading down the pipe, your pipe.

Angband mutation flatulence