Lactose is a type of sugar that’s in milk & dairy products. Our bodies digest this by using an enzyme lactase. Some people don’t have enough of this (mainly Blacks, Asians, and Native Americans); some people don’t have any. So if we can’t digest lactose, we get symptoms like diarrhea, boating, gas, abdominal pain or discomfort.
The easiest do-it-yourself diagnosis is to drink 2 large glasses of milk without eating, or to eat several servings of dairy food one day. If symptoms occur, stop all dairy products. You’ll feel better in a few days — then, a week or two later, do it again (“rechallenge”). If it all comes back, you’ve got the diagnosis.
There’s a simple breath test to prove the diagnosis, that can be done by a Gastroenterologist. This might be recommended for people who absolutely love their dairy foods, and don’t want to spend a lifetime avoiding them, or having to take lactase pills every time they eat or drink them (they should be taken immediately beforehand). The breath test is especially useful for Whites, to confirm that their symptoms aren’t (or are) psychological, since Caucasians rarely get lactose intolerance to begin with. But the breath test may be false-negative 15% to 20% of the time.