Introduction 

Lactose intolerance is a common digestive problem where the body is unable to digest lactose, a type of sugar mainly found in milk and dairy products.

Symptoms of lactose intolerance include:

These symptoms usually develop within a few hours of consuming food or drink that contains lactose.

Read more about the symptoms of lactose intolerance.

When to seek medical advice

The symptoms of lactose intolerance can be similar to several other conditions, such as irritable bowel syndrome (IBS), so it's important to see your GP for a diagnosis before removing milk and dairy products from your diet.

If your GP thinks you are likely to have lactose intolerance, they may then suggest avoiding foods and drinks containing lactose for two weeks to see if your symptoms improve.

Read more about diagnosing lactose intolerance.

What causes lactose intolerance?

The body digests lactose using a substance called lactase to break down lactose into two sugars called glucose and galactose, which can then be easily absorbed into the bloodstream.

People with lactose intolerance don't produce enough lactase, so lactose stays in the digestive system where it is fermented by bacteria, leading to the production of various gases, which cause the symptoms associated with lactose intolerance.

Depending on the underlying reason why the body does not produce enough lactase, lactose intolerance may be temporary or permanent. Most cases that develop in adults are inherited and tend to be lifelong, but cases in young children are often caused by an infection in the digestive system and may only last for a few weeks.

Read more about the causes of lactose intolerance.

Is it an allergy?

Lactose intolerance is not the same as a milk or dairy allergy. Food allergies are caused by a reaction to a food by your immune system, causing symptoms such as a rash, wheezing and itching.

If you’re allergic to something, even a tiny particle can be enough to trigger a reaction, while most people with lactose intolerance can still consume small amounts of lactose without experiencing any problems (although this varies from person to person).

Treating lactose intolerance

There is no cure for lactose intolerance, but limiting your intake of food and drink containing lactose will usually help control the symptoms.

Depending on what dairy products you are able to eat, you may also require additional calcium and vitamin D supplements to keep your bones strong and healthy. In some cases, your GP may refer you to a dietitian for further advice.

In addition to dietary changes, lactase substitutes may also be helpful. These are drops or tablets you can take with your meals or drinks to improve your digestion of lactose.

Read more about treating lactose intolerance.

Who is affected

Rates of lactose intolerance can differ significantly between different ethnic groups. For example, it is thought that only one in 50 people of northern European descent have some degree of lactose intolerance, whereas most people of Chinese descent have the condition.

This may be because people from places where there has historically been no ready access to milk, such as Africa or east Asia, may not have evolved the ability to digest lactose as there was no significant benefit in being able to do so.

In the UK, lactose intolerance is more common in people of Asian or African-Caribbean descent.

Lactose intolerance can develop at any age. Many cases first develop in people aged 20 to 40, although babies and young children can also be affected.




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Page last reviewed: 28/04/2014

Next review due: 28/04/2016