It's extremely common—here's what it feels like.

By Maggie O'Neill
Updated December 31, 2019
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Ice cream, cheese, coffee with cream: Many of life's edible pleasures contain dairy in some way, shape, or form—and those pleasures may lead to discomfort for more than half of the entire human race.

Yep, that's right: The majority of human beings—about 65 percent, according to the U.S. National Library of Medicine—are somewhat unable to digest lactose. (You may know this as lactose intolerance, but more on that in a sec.) And since the condition is so common, it's wise to know what it is, and what symptoms are associated with it—even if that information brings you to the realization that maybe pizza and milkshakes shouldn't be part of your daily diet.

What exactly is lactose intolerance?

So, lactose is a sugar that’s found in dairy products. The body breaks it down by way of a substance called lactase. Cells found in the small intestine are responsible for producing lactase, and when the body doesn't produce enough lactase to properly break down lactose, it's known as lactose malabsorption.

Here's where it gets tricky: When you start showing symptoms due to your body's lactose malabsorption, that's known as lactose intolerance, per the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

That's because those with lactose malabsorption still technically produce enough lactase for their bodies to break down lactose well enough not to experience symptoms. But what if dairy does make you feel some type of (not so good) way? Here, a gastroenterologist explains the symptoms of lactose intolerance, and when to know if you need to cut dairy out of your life for good.

What are lactose intolerance symptoms?

The symptoms of lactose intolerance typically come on a few hours after ingesting dairy products, and per the NIDDK, include:

  • abdominal pain
  • diarrhea
  • gas
  • nausea
  • bloating
  • stomach “growling” or rumbling sounds
  • vomiting

The first three—diarrhea, gas, and abdominal pain—are the most common symptoms, Rabia de Latour, MD, gastroenterologist and assistant professor of medicine at NYU Langone Health, tells Health. But why do they happen? According to the NIDDK, when that undigested lactose makes its way to your colon, bacteria that live there break it down, creating extra fluid and gas that your body has to expel.

So, what can you do about lactose intolerance?

Doctors diagnose lactose intolerance a few different ways. “Most of the time it’s clinical diagnosis,” says Dr. de Latour. She adds that patients will say something along the lines of, “Every time I have milk in my coffee, I get these symptoms.” When patients explain that, it signals to the physician that it could be a lactose issue.

Your doctor may also ask you to keep a food diary. Writing down what you eat might make you more aware of what’s causing your stomach to hurt. Additionally, your doctor might perform an endoscopy (a procedure in which your doctor sticks a camera down your throat to get a better look at your gastrointestinal tract) during the diagnostic process.

The good news is that even if you have a lactose intolerance, the condition is easily managed. As you probably guessed, it consists of limiting or eliminating lactose-containing foods. Dr. de Latour explains that lactose intolerance is “not a super dangerous disease to have—just inconvenient.”

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