Lactose Intolerance: Three Signs are Named

Loose stools after eating dairy products are a sure sign of lactose intolerance. If a glass of milk or a scoop of ice cream is causing damage to your stomach, you are probably dealing with lactose intolerance, a condition characterized by an inability to fully digest lactose (the natural sugar in milk and dairy products).

Although an upset stomach after eating dairy products can signal lactose intolerance, the symptom pattern is unique to each individual.

Some people may have certain symptoms and others may not, and these symptoms may also vary depending on the foods eaten and the amount of lactose they contain.

Here, Dr. De Latour explains the common symptoms that can occur with lactose intolerance, as well as how to diagnose and treat the condition.


Loose stools after eating dairy products are a sure sign of lactose intolerance.

Here’s why: due to a lack of the enzyme lactase, lactose cannot be broken down. As a result, undigested lactose in the intestines will draw water into the colon and cause diarrhea, says Dr. De Latour.

Nausea, stomach cramps, and bloating

When you can’t digest lactose, it travels to the colon where intestinal bacteria can break it down. This process produces gases that cause bloating, cramping, and pain,” says Dr. De Latour.

Moreover, bloating can cause nausea and vomiting, she adds.


“Although constipation is a less common sign of lactose intolerance, technically speaking, it can happen,” says Dr. De Latour.

“As the bacteria in the colon break down undigested lactose, it produces methane gas, which can slow down the bowel movement,” explains Dr. De Latour. “Slowing down the bowels allows the colon to pull more water out of the stool, which can cause constipation.”

What to do if you think you are lactose intolerant

First, note what dairy products you eat and when you experience stomach discomfort or digestive problems. From there, try eliminating these foods from your diet for a few days to see if your symptoms improve, according to the Mayo Clinic.

But for a definitive diagnosis, you should see a doctor who will run tests to assess your lactose intolerance.

One of these tests, the hydrogen breath test, calculates the amount of hydrogen in your breath after drinking a lactose-rich beverage, according to the Mayo Clinic. Too much hydrogen shows that you are not digesting and absorbing lactose properly.

There is also a blood test that determines the amount of glucose in your bloodstream after you have drunk a lactose-based beverage. In this case, if your glucose level does not rise, it means that your body is not digesting and absorbing lactose, according to the Mayo Clinic.

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Written by Emma Miller

I am a registered dietitian nutritionist and own a private nutrition practice, where I provide one-on-one nutritional counseling to patients. I specialize in chronic disease prevention/ management, vegan/ vegetarian nutrition, pre-natal/ postpartum nutrition, wellness coaching, medical nutrition therapy, and weight management.

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