This factsheet is for people who have lactose intolerance, or who would like information about it.
Lactose intolerance is when your body is unable to break down lactose (a sugar found in milk).
Lactose is a sugar found in milk and other dairy products. Usually, your body breaks it down into two simpler sugars, called glucose and galactose, by a chemical (enzyme) called lactase. Lactase is made in the inner lining of your small bowel. Once lactose has been broken down, it's absorbed from your bowel into your bloodstream.
Lactose intolerance develops when your body doesn’t make enough lactase. If you don't produce enough lactase, then you won’t be able to digest or absorb lactose properly from your bowel. When this happens, you get the symptoms of lactose intolerance.
Lactose intolerance usually affects older children and adults because your levels of lactase start to decrease naturally as you get older. Some children are born with lactose intolerance because they don't have any lactase at all from birth, but this is rare. Sometimes you can have lactose intolerance temporarily because the lining of your small bowel (where lactase is produced) has been damaged. This is called secondary lactose intolerance.
In the UK, around five in 100 people have lactose intolerance. It’s more common in countries where milk isn't part of the usual adult diet, such as South America, Africa and Asia.
The symptoms of lactose intolerance appear after you’ve consumed something that contains lactose – and include:
These symptoms may be caused by problems other than lactose intolerance. If you have any of these symptoms, see your GP for advice.
If you have lactose intolerance and don’t include enough alternative sources of calcium in your diet, you’re bones may become weaker and you can develop a condition known as osteopenia.
Babies born with lactose intolerance (congenital lactase deficiency) don’t put on weight as they should and will show signs of not getting enough nutrients. They will need to be fed a special diet from birth.
Lactose intolerance develops when you have a shortage of the enzyme lactase in your body. There are three main causes of lactose intolerance.
Your GP will ask about your symptoms and examine you. He or she may ask you to keep a diary of your symptoms and what you consume on a day-to-day basis. This will help your GP to look for any links between your symptoms and what you eat and drink.
To confirm whether you have lactose intolerance, your GP may suggest you completely remove dairy products from your diet for a trial period of two or three weeks. If your symptoms are relieved during this time, it's likely that you have lactose intolerance.
If you think your child may have the symptoms of lactose intolerance, your GP may ask for a sample of his or her faeces (stool sample), which will be sent away for testing. This is called a stool acidity test.
Having specific tests to diagnose lactose intolerance is uncommon. If there is uncertainty about your diagnosis, you may be referred to a specialist doctor for further tests. He or she may ask you to have one or more of the following.
There isn’t a cure for lactose intolerance, but you can control your symptoms by reducing the amount of lactose in your diet.
Most people who have lactose intolerance can have a small amount of milk (around 200ml) with a meal, without reacting to it. You could try drinking small amounts of milk to find out how much you can tolerate without having any symptoms.
You should try to include cheese, yoghurt and low lactose milk in your diet as dairy products are a good source of calcium. You can buy milk and other products that contain a reduced amount of lactose from supermarkets. Hard cheeses, such as cheddar, edam and parmesan only contain a small amount of lactose, so you will usually be able to eat these without having any symptoms. You may also find that you're able to eat yoghurt without any problems. This is thought to be partly because there is an enzyme similar to lactase found in the bacteria that is used to produce yoghurt.
You can also buy lactase preparations, either as a liquid that you add to milk, or as tablets that you take before consuming something containing lactose.
If you're very sensitive to lactose, remember that it's often found in some processed food products such as bread, meats and some drinks, such as lagers and beers. Check the labels for ingredients.
If you're unable to eat any dairy foods, you may not be getting enough calcium in your diet. Non-dairy foods that contain calcium include green leafy vegetables, soya beans, tofu and nuts. Talk to your GP about your diet and he or she may refer you to a dietician for help and support.
For answers to frequently asked questions on this topic, see FAQs.
For sources and links to further information, see Resources.
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This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.
Produced by Krysta Munford, Bupa Health Information Team, February 2012.