While we all start out as milk-guzzling champs, it is not unusual to lose our tolerance for all manner of dairy as we get older. In fact, between 60-75% of the world is lactose intolerant, says Robynne Chutkan, MD, founder of The Digestive Center For Women in Chevy Chase, MD. And per the U.S. National Library of Medicine, around 30 million American adults have some degree of lactose intolerance by age 20. When you think about the fact that humans are really the only species to drink the milk of another animal as adults, it’s not surprising that lactose intolerance is so common. But because dairy is quite the staple in the American diet, a lot of people may not even realize it's affecting them. “Some people get gas and bloating every day, and they’re consuming dairy every day in some form or another, but they never put it together,” Dr. Chutkan says. “They just think, Oh, I’m a gassy person, and they don’t realize that it’s because of the dairy consumption.”
So what exactly is lactose intolerance, and how do you tell if you really have it? Essentially, lactose intolerance just means your body has trouble digesting lactose, a type of sugar that’s naturally found in milk and other dairy products. It’s not the same thing as a food allergy, as lactose intolerance tends to be way less severe. If you have a true allergy to dairy products, you’ll likely develop hives or have bloody stool, and you might be susceptible to a life-threatening allergic reaction called anaphylaxis. That's why people with a milk allergy must avoid milk. However, people with lactose intolerance can get away with having milk and dairy; they may just have to suffer through the gas and bloating, which are the most common (and the most mild) symptoms, Dr. Chutkan says.
Some people may have stronger, more uncomfortable reactions to lactose. These symptoms include diarrhea or loose stool after ingesting something with lactose in it. Vomiting, stomach cramps, or rumbling sounds in your belly are also possible. Typically, symptoms will begin between about 30 minutes to two hours after eating or drinking milk products.
While a lot of people may notice these symptoms and cut dairy out themselves, it's a good idea to see your doctor to make sure it's really lactose intolerance. To test your tolerance, your doctor will likely use one of two common methods: a blood test, or a hydrogen breath test. The hydrogen breath test is the preferred method, but it's a little more intricate; you’ll be asked to breathe into a balloon-like container and then drink a sample of something containing lactose. Samples of your breath will then be taken and checked for hydrogen levels, which increase when your body has trouble breaking down and absorbing lactose. If you do happen to be lactose intolerant, don’t worry — there are lots of alternatives to milk, such as almond milk, soy milk, cashew milk, and rice milk. And if you’re lamenting the fact that you might not be able to eat as much ice cream as you’d like, there are plenty of alternative options out there for that, too. If you’re worried about getting the calcium you need, Dr. Chutkan recommends eating leafy greens and small-boned fish (both are also great sources of calcium), and getting regular exercise. The important thing is to remember not to push your body to ingest lactose if it can’t. “When you’re lactose intolerant, you shouldn’t drink milk,” Dr. Chutkan says. “That’s your body saying ‘no please, you can’t digest this, it’s not a good idea for you.’”