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Lactose Intolerance: 4 Symptoms and How to Treat It

Your stomach issues may be caused by eating too much dairy. Learn about the symptoms and whether you’re lactose intolerant.

What is lactose intolerance?

Pro Tip

There are a few things people don’t realize about lactose intolerance. It is super common. It can be temporary or permanent. And the likelihood of developing it increases with age. —Dr. Shria Kumar

Lactose intolerance means that you have difficulty digesting lactose, a sugar found in milk and milk products. It happens because you don't have enough of the enzyme, lactase, which helps your body digest it.

It can cause an upset stomach, bloating, abdominal pain, gas, and diarrhea after eating or drinking dairy products such as milk, cheese, and ice cream.

Avoiding dairy products or taking a lactase supplement while eating dairy can prevent the symptoms.

Lactose intolerance is not a milk allergy. It is relatively common, and is especially common in people of East Asian descent (70% or more have it).

What is causing your symptoms?

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What are symptoms of being lactose intolerant?

Lactose intolerance causes upset stomach, abdominal pain, gas, and diarrhea after eating or drinking milk or milk products. Nausea and vomiting is a less common symptom.

Symptoms may start anywhere from 30 minutes to 2 hours after having dairy products. They can last for a few hours to a day afterwards, and may be relieved by having a bowel movement.

Can kids be lactose intolerant?

Lactose intolerance is rare in children under 5. If a young child repeatedly complains of an upset stomach and other digestive issues, the cause may be a virus, Crohn’s or celiac disease, or an allergy to cow’s milk.

Children over age 5 can develop lactose intolerance. Symptoms are similar to what adults experience.

It’s essential to first talk to your pediatrician before cutting lactose out of your child’s diet, even just as a test. Milk is an important source of calories, calcium, protein, and vitamin D. You will need to replace these nutrients with other foods if your child is diagnosed as lactose intolerant.

What foods to avoid if you are lactose intolerant

Dr. Rx

People often think: Once I have lactose intolerance I cannot eat any milk products for the rest of my life. But it does not necessarily mean lactose-containing foods are cut out for the rest of your life! Plus, there are many great alternative products. Trial different ones—tell your doctor you’re avoiding lactose—and see what works best for you. —Dr. Kumar

If you repeatedly have an upset stomach, think about whether you ate dairy foods before the symptoms started. If so, you may have lactose intolerance.

Try eliminating dairy products for 2 weeks to see whether that makes symptoms go away. If symptoms improve, you are likely lactose intolerant. If not, you may have another issue. Testing is also an option if the diagnosis remains unclear. Your doctor can help set up a test if this is the case.

If you’re lactose intolerant, the treatment is prevention. The surest way to stop your symptoms is to avoid dairy products altogether. However, some people with lactose intolerance can eat smaller amounts of dairy without symptoms. You may need to figure out the amount of lactose you can tolerate by trying to have a little at a time.

You will need to replace the nutrients you would normally get from dairy products like vitamin D and calcium.

One option is to eat lactose-free dairy products including lactose-free milk (Lactaid) and ice cream.

People with milder symptoms often take an over-the-counter pill that contains the enzyme lactase. This helps break down lactose and prevents symptoms. Talk to your doctor before doing this.

Other good sources of calcium are dark green leafy vegetables such as spinach, broccoli, and kale, as well as certain nuts (almonds), beans (white beans), fish (sardines, salmon), and calcium-fortified orange juice.

Sometimes people want to try reintroducing foods containing lactose to see if tolerance has improved. This should only be done with a doctor’s guidance, though often happens inadvertently (i.e. you realize you ate a dairy containing food and had no trouble!) Many people (but not all) outgrow this.

Lactose intolerance causes

Lactase is a specific enzyme in the small intestine. Lactase helps break down the lactose (sugar) in dairy products. In people with lactose intolerance, their small intestine doesn’t produce enough lactase to digest all of the lactose in the dairy products such as milk, ice cream, pudding, and soft cheeses. In rare instances, people are born without the ability to make any lactase at all.

The lactose that is not digested moves into the large intestine (colon), which breaks it down, but that creates fluid and gas. This leads to pain, bloating, diarrhea, and other symptoms.

With age, there is a normal, gradual reduction in lactase. The rate of decline of your lactase production depends on your genes, which is why lactose intolerance symptoms can arise at different ages.

In addition, injuries to the small intestine—from a viral infection (stomach bug), a disease like Crohn’s disease or celiac, or from taking certain medications (chemotherapies)—can also reduce the amount of lactase your body makes. These are typically more temporary conditions.

Pro Tip

The symptoms people experience with lactose intolerance vary from person to person. It depends on the individual, what lactose-containing food they ate, and how much they ate. Though when someone tells me, I had ice cream and a few hours later I was having belly pain and diarrhea, it is probably because of lactose intolerance. —Dr. Kumar

Wondering if you have lactose intolerance?

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Risk factors

Some ethnic groups are much more likely to be lactose intolerant. People of African, Asian, and Hispanic descent, and Native Americans have the highest rates of lactose intolerance. Lactose intolerance rates increase with age among all races.

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