What is lactose intolerance?

Lactose intolerance is when your body can't break down or digest lactose. Lactose is a sugar found in milk and milk products.

Lactose intolerance happens when your small intestine does not make enough of a digestive enzyme called lactase. Lactase breaks down the lactose in food so your body can absorb it. People who are lactose intolerant have unpleasant symptoms after eating or drinking milk or milk products. These symptoms include bloating, diarrhea and gas.

Lactose intolerance is not the same thing as having a food allergy to milk.

Lactose intolerance is most common in Asian Americans, African Americans, Mexican Americans, and Native Americans.

What causes lactose intolerance?

Both children and adults can have lactose intolerance. Here are some common causes of this condition:

• Lactose intolerance often runs in families (hereditary). In these cases, over time a person’s body may make less of the lactase enzyme. Symptoms may start during the teen or adult years.
• In some cases, the small intestine stops making lactase after an injury or after a disease or infection.  
• Some babies born too early (premature babies) may not be able to make enough lactase. This is often a short-term problem that goes away.
• In very rare cases, people are born with an inability to make any lactase at all.

What are the symptoms of lactose intolerance?

Each person’s symptoms may vary. Symptoms often start about 30 minutes to 2 hours after you have food or drinks that have lactose.

Symptoms may include:

• Belly (abdominal) cramps and pain
• Nausea
• Bloating
• Gas
• Diarrhea

How severe your symptoms are will depend on how much lactose you have ingested and how much lactase your body makes.

The symptoms of lactose intolerance may look like those of other health problems. Always see your healthcare provider to be sure.

How is lactose intolerance diagnosed?

Your healthcare provider will talk to you about your past health and family history. He or she will give you a physical exam.

You may be asked not to have any milk or milk products for a short time to see if your symptoms get better.

Some tests can help your doctor check for lactose intolerance. These may include:

• Lactose tolerance test. This test checks how your digestive system absorbs lactose. You will be asked not to eat or drink anything for about 8 hours before the test. This often means not eating after midnight. For the test, you will drink a liquid that contains lactose. Some blood samples will be taken over a 2-hour period. These will check your blood sugar (blood glucose) level. If your blood sugar levels don’t rise, you may be lactose intolerant.
• Hydrogen breath test. You will drink a liquid containing a lot of lactose. Your breath will be checked several times. High levels of hydrogen in your breath may mean you are lactose intolerant.
• Stool acidity test. This test is used for infants and young children. It checks how much acid is in the stool. If someone is not digesting lactose, their stool will have lactic acid, glucose, and other fatty acids.  

How is lactose intolerance treated?

There is no treatment that can help your body make more lactase. But you can manage your symptoms by changing your diet.

In the past, people who were lactose intolerant were told to avoid dairy products. Today, health experts suggest you try different dairy foods and see which ones cause fewer symptoms. That way you can still get enough calcium and other important nutrients.

Lactose intolerance symptoms can be unpleasant, but they won’t hurt you. So try to find dairy foods that don’t cause severe symptoms.

Here are some tips for managing lactose in your diet:

• Start slowly. Try adding small amounts of milk or milk products and see how your body reacts.
• Have milk and milk products with other foods. You may find you have fewer symptoms if you take milk or milk products with your meals. Try eating cheese with crackers or having milk with cereal.   
• Eat dairy products with naturally lower levels of lactose. These include hard cheeses and yogurt.
• Look for lactose-free and lactose-reduced milk and milk products. These can be found at many food stores. They are the same as regular milk and milk products, but they have the lactase enzyme added to them.
• Ask about lactase products. Ask your healthcare provider if you should take a lactase pill or lactase drops when you eat or drink milk products.

If you have trouble finding dairy products that don’t cause symptoms, talk to your healthcare provider. He or she can suggest other foods to be sure you get enough calcium. You may need to take calcium supplements.

Children with lactose intolerance should be seen by a healthcare provider. Children and teenagers need dairy foods. They are a major source of calcium for bone growth and other nutrients essential to children’s health and development.

Living with lactose intolerance

Lactose intolerance can affect you every time you eat a snack or meal. So you need to be careful about the foods you eat every day. However, many people can tolerate a certain amount of lactose and don't need to completely avoid it.

It’s important to read food labels. Lactose is often added to some boxed, canned, frozen, and prepared foods such as:

• Bread
• Cereal
• Lunch meats
• Salad dressings
• Cake and cookie mixes
• Coffee creamers

Check food labels for words that may mean a food has lactose in it, such as:

• Butter
• Cheese
• Cream
• Dried milk
• Milk solids
• Powdered milk
• Whey

When should I call my healthcare provider?

Call your healthcare provider if you have trouble managing your symptoms. Some symptoms can be embarrassing. Your healthcare provider can work with you to help keep them under control.