Lactose intolerance means your body can’t break down lactose (a sugar mainly found in milk).
Lactose is a sugar found in milk and other dairy products. An enzyme (a type of chemical) called lactase, which is produced by your small bowel, breaks lactose down into two simpler sugars (glucose and galactose). Once lactose has been broken down, it's absorbed from your bowel into your bloodstream.
If your body doesn’t make enough lactase, you may develop symptoms of lactose intolerance. Lactose intolerance usually affects older children and adults because the level of lactase starts to decrease naturally as you get older.
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 can occur after you’ve eaten or drunk something that contains lactose. Symptoms of lactose intolerance may include:
These symptoms may be caused by problems other than lactose intolerance. If you have any of these symptoms for more than a few days see your GP for advice.
If you have lactose intolerance, you can control your symptoms by reducing the amount of lactose in your diet. However, the lack of dairy products in your diet will mean you need to get vitamin D and the mineral calcium, from other sources. If you don’t get enough calcium in your diet, your bones may become weak and you may develop a condition known as osteopenia.
Babies born with the rare but more severe form of lactose intolerance may not grow as they should if they don’t receive the right nutrients. They will need to be fed a lactose-free formula from birth.
Lactase deficiency is when your body doesn’t produce enough lactase, which can lead to symptoms of lactose intolerance.
There are three main types of lactase deficiency.
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 eat and drink on a day-to-day basis. This will help your GP to look for any links between your symptoms and your diet.
Your GP may suggest you completely remove foods and drinks containing lactose from your diet for a trial period of two weeks. If your symptoms get better during this time, but come back when you start having lactose again, it's likely that you have lactose intolerance.
If you think your child may have symptoms of lactose intolerance, your GP may ask for a sample of his or her faeces (stool sample). This will be sent away for testing to check if your child’s body is absorbing lactose.
Having specific tests to diagnose if you have lactose intolerance is uncommon. However, if there is uncertainty about your diagnosis, your GP may refer you to have one or more of the following tests.
There isn’t a cure for lactose intolerance, but you can control your symptoms. Milk and dairy products are the main sources of lactose and cutting down how much of these products you have may help your symptoms. We’ve put together some tips to help you with this.
If you can’t 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 if you have any questions. He or she may refer you to a dietitian for help and support. Your GP may also recommend that you take calcium and vitamin D supplements.
Reviewed by Kuljeet Battoo, Bupa Health Information Team, July 2014.
For answers to frequently asked questions on this topic, see FAQs.
For sources and links to further information, see Resources.
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.