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Lactose intolerance: Overview

Last Update: June 17, 2015; Next update: 2018.


Stomach ache, bloating, "gas" and diarrhea are all typical digestive symptoms that some people have after eating or drinking dairy products. People who have difficulty digesting dairy products may only tolerate small amounts of lactose (a sugar found in milk and other dairy products). This is called lactose intolerance.

But some people who are sensitive to milk might actually have a different problem. It is important to get the diagnosis right before deciding to make major changes to your diet, especially in children, teenagers and people who need more calcium.

Lactose intolerance is not an allergy. This is an important difference. People who have a true milk allergy can react to even a tiny amount of dairy foods or milk. But people who are lactose intolerant can sometimes consume quite a lot of these products without having any major problems.


Symptoms are normally noticed shortly after eating or drinking dairy products. The amount of lactose that causes symptoms varies from person to person. Symptoms may include the following: 


Babies' digestive systems are designed to survive only on breast milk. In order to digest milk, babies produce the enzyme lactase. It breaks down the kind of sugar found in milk - lactose - in the bowel so that the body can process it further.

When a child is weaned off breast milk, the digestive system gradually adapts to other foods. The body then produces considerably less lactase, and can therefore only break down smaller amounts of lactose. This naturally occurring form of lactose intolerance is also known as primary or innate lactose intolerance.

The amount of lactose an adult can digest varies, and genetic predisposition also plays a role. While relatively few Northern Europeans have lactose intolerance, it is common in Asian or African people.

People with lactose intolerance either have much less lactase or cannot absorb lactose as well as people who tolerate dairy products.

In acquired or secondary lactose intolerance, the small intestine starts producing too little lactase. This may be caused by chronic inflammation of or damage to the lining of the intestine. It is then important to treat the underlying problem.


Lactose intolerance is very rare in children under the age of five. It typically develops during adolescence or adulthood. Worldwide, lactose intolerance is very common, but there are significant differences between regions and populations.

About 5 to 15% of Europeans have lactose intolerance. It is least common in Northern Europe. In contrast, it is estimated that 65 to 90% of adults in Africa and East Asia are affected.


To diagnose lactose intolerance, an elimination diet can be done, followed by a lactose intolerance test. This involves avoiding milk or dairy products for a certain time, and then consuming a certain amount of lactose again. The body's reaction to that is then monitored.

A lactose intolerance test measures blood sugar levels before and several times after drinking a lactose solution. This makes it possible to find out whether the body is able to break down and absorb the lactose.

A breath test can also be done. This measures the hydrogen content of your breath, which is normally higher in people who have lactose intolerance.

Everyday life

Although lactose intolerance cannot be cured, it is still possible to live a symptom-free life by changing your diet. Dairy products are not essential for a balanced diet, but you do need to make sure you get enough calcium. Good sources of calcium include green vegetables such as spinach and green cabbage, and calcium-rich mineral water. Aged cheeses such as parmesan or older gouda also contain a lot of calcium. These foods are usually tolerated well by people with lactose intolerance.

If you find it too hard to give up dairy completely, you can test how much lactose you tolerate and then spread that amount out across your day in combination with other foods.

People with severe lactose intolerance usually do not eat any dairy products, although it can be difficult to avoid them if you eat out. Instant meals also often contain lactose. Some people then take dietary supplements to prevent symptoms.

Dietary supplements containing the enzyme lactase are available in tablet and capsule form to help the body break down lactose. People who take them hope to be able to better tolerate foods containing lactose,  but no studies have proven this effect. The few studies that were done on dietary supplements did not show that the products were able to relieve or prevent symptoms.


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  • IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

    Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. We do not offer individual consultations.

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