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Lactose intolerance
Published by Bupa’s Health Information Team, March 2010.
This factsheet is for people who have lactose intolerance, or who would like information about it.
Lactose intolerance is when the body is unable to break down lactose (a sugar found in milk).
About lactose intolerance
Symptoms of lactose intolerance
Complications of lactose intolerance
Causes of lactose intolerance
Diagnosis of lactose intolerance
Treatment of lactose intolerance
About lactose intolerance
Lactose is a sugar found in milk. It’s usually broken down into two simpler sugars, called glucose and galactose, by an enzyme called lactase. Lactase is produced 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 happens when you have a shortage of lactase. If you don’t have enough lactase, lactose can’t be digested and absorbed from your bowel properly, causing the symptoms of lactose intolerance.
Lactose intolerance usually affects adults, as your levels of lactase start to decrease after childhood. Some children are born with lactose intolerance, as they don’t have any lactase at all from birth, but this is rare.
Lactose intolerance is more common in certain countries and ethnic groups. It’s common in places where milk isn’t part of the usual adult diet. For example in South America, Africa and Asia, more than half of people have lactose intolerance.
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.
Symptoms of lactose intolerance
The symptoms of lactose intolerance appear after you have eaten or drunk something that contains lactose. They are usually mild. Symptoms include:
- nausea
- feeling bloated
- stomach pains or cramps
- diarrhoea
- flatulence
- loud bowel sounds
- an urgent need to have a bowel movement between 30 minutes and two hours after eating or drinking something that contains lactose
These symptoms may be caused by problems other than lactose intolerance. If you have any of these symptoms, see your GP for advice.
Complications of lactose intolerance
Sometimes lactose intolerance can cause severe diarrhoea. This can prevent your body absorbing important nutrients because they are removed from your body too quickly. Severe diarrhoea can also lead to dehydration.
Causes of lactose intolerance
Lactose intolerance happens when you have a shortage of the enzyme lactase. There are three main causes of lactose intolerance.
- Primary lactase deficiency. This is a gradual reduction in lactase production as you get older.
- Congential lactase deficiency. This means you have inherited a rare disorder where you produce little or no lactase.
- Secondary lactose intolerance. This is when a separate condition damages the lining of your bowel and reduces the amount of lactase you produce. Diseases of your digestive system including gastroenteritis, irritable bowel syndrome, coeliac disease and cancer or injuries can cause secondary lactose intolerance. It’s usually only temporary and your symptoms should disappear within two to four weeks. However, if it’s caused by a long-term condition it may be permanent.
Diagnosis of lactose intolerance
Your GP will ask about your symptoms. He or she may ask you to drink a test glass of milk to see if this triggers your symptoms.
Your doctor may take a blood sample after you have drunk some milk, to measure your blood sugar (glucose) level. If your blood sugar level increases by only a small amount or don’t increase at all, this suggests that lactose hasn’t been digested and absorbed into your bloodstream, and is a sign that you may have lactose intolerance.
Your GP may ask you for a sample of faeces (stool sample), which will be sent away for testing. Your stool sample will be tested for acids that are produced by undigested lactose in your bowel, such as lactic acid. This is called a stool acidity test.
Your GP may ask you to remove dairy products from your diet for a trial period of three or four weeks. If you have no symptoms during this time, it’s likely that you have lactose intolerance.
Your GP may refer you to a specialist for further tests, which may include the following.
- Hydrogen breath test. Your doctor will measure the level of hydrogen in your breath after you have drunk some milk. If there is a large amount of hydrogen in your breath, this may be a sign that you have lactose intolerance. This is because hydrogen is formed when bacteria in your bowel act on undigested lactose.
- Biopsy. You may need to have a biopsy (a small sample of tissue) taken from the lining of your small bowel. This is done using an endoscope - a flexible, tube-like instrument. The sample will be sent to a laboratory to be tested for lactase.
Treatment of lactose intolerance
There is no cure for lactose intolerance. However, you can control your symptoms by reducing the amount of lactose in your diet.
Most people with lactose intolerance can have a small amount of milk (around 200ml) with a meal, without reacting to it. Try experimenting to find out how much lactose you can tolerate without having any symptoms.
You can buy milk and other products that contain a reduced amount of lactose from supermarkets. You can also buy lactase preparations, either as a liquid that you add to milk, or as tablets that you take before eating or drinking something containing lactose.
Try to include cheese, yoghurt and low lactose milk in your diet, as dairy products are a good source of calcium and vitamins. 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.
If you’re very sensitive to lactose, remember that it’s often found in ready-made meals and other processed food products. Check the labels for ingredients.
If you’re unable to eat any dairy foods, you may not be getting enough calcium in your diet. Talk to your GP about your diet, and try to include non-dairy sources of calcium. Non-dairy foods that contain calcium include green leafy vegetables such as broccoli and cabbage, soya beans, tofu, nuts and fish where you eat the bones, such as sardines and pilchards.
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Published by Bupa’s Health Information Team, March 2010.
This section contains answers to common questions about this topic. Questions have been suggested by health professionals, website feedback and requests via email.
Is lactose intolerance the same as a milk allergy?
Is it possible that my baby has lactose intolerance?
Can I drink soya milk if I have lactose intolerance?
Is lactose intolerance the same as a milk allergy?
No. If you have lactose intolerance it means your body is unable to break down a sugar in milk called lactose. However, if you have a milk allergy it means you’re allergic to some of the proteins in milk.
Explanation
Milk allergy and lactose intolerance are often confused, because they both occur after eating or drinking dairy products and they can cause similar symptoms.
However, lactose intolerance tends to affect older children and adults whereas milk allergy is much more common in babies and young children. It’s important to determine which one you have, as milk allergy can sometimes cause severe reactions.
If you have lactose intolerance, it means your body has a shortage of a chemical called lactase, which is needed to break down the lactose in milk. The undigested lactose can cause digestive problems, such as diarrhoea and bloating.
If you have an allergy to milk, your body’s immune system mistakes some of the proteins found in milk as harmful, leading to an allergic reaction. Although an allergic reaction to milk can cause some similar symptoms to lactose intolerance, it can also cause allergic reactions throughout your body, such as difficulty breathing and hives (red, itchy swellings on your skin). Children who have milk allergy may also have other allergy-related conditions, such as eczema. If you have a milk allergy, you may react after having just a small amount of milk, whereas if you have lactose intolerance, you may be able to have some dairy products without feeling ill.
Milk allergies are more common in children, but most children grow out of them by the age of three. So it’s rare to have a milk allergy as an adult. Lactose intolerance usually affects adults, and it’s very rare for young children or babies to have it.
If you or your child feels unwell after drinking milk or eating dairy products, see your GP. Don’t cut milk or dairy products out of your or your child’s diet without talking to a health professional first.
Further information
- British Nutrition Foundation
- Food Standards Agency
Sources
- Lactose intolerance. Food Standards Agency. www.eatwell.gov.uk, accessed 4 February 2010
- Milk allergy and intolerance. Food Standards Agency. www.eatwell.gov.uk, accessed 4 February 2010
- Lactose intolerance and the breastfed baby. Australian Breastfeeding Association. www.breastfeeding.asn.au, accessed 8 February 2009
- Lactose intolerance. British Nutrition Foundation. www.nutrition.org.uk, accessed 8 February 2010
- Simon C, Everitt H, van Dorp F. Oxford handbook of general practice. 3rd ed. Oxford: Oxford University Press, 2010:886-87
Is it possible that my baby has lactose intolerance?
It’s possible, but it’s extremely rare for babies to be born with lactose intolerance.
Explanation
Lactose intolerance usually develops in older children and adults, as the level of lactase in your body decreases as you get older. It’s possible for babies to be born without any lactase in their bodies. However, this is very rare. If your baby is born with lactose intolerance, he or she won’t grow as expected and will show obvious signs of not getting enough fluid and nutrients. He or she will need to be fed a special diet from soon after birth.
If your baby is having symptoms such as diarrhoea and vomiting after feeding, it’s more likely to be due to a milk allergy or intolerance, rather than lactose intolerance. See your GP if your baby has these symptoms after feeding.
It’s possible for your baby to develop secondary lactose intolerance as a result of another illness, such as gastroenteritis. Secondary lactose intolerance is temporary, and your baby’s symptoms will usually disappear within two to four weeks, once his or her gut has healed.
Lactose overload can also be mistaken for lactose intolerance in babies. This is when a baby consumes such a large amount of milk, that he or she is unable to digest all of the lactose, leading to pain in his or her tummy (abdomen). Your baby may pass urine more than ten times a day and have many (often explosive) bowel movements. It can become a vicious cycle as your baby may show signs of being hungry, as feeding can temporarily ease his or her pain. However, another feed can cause the problem to worsen.
If your baby seems to be having problems with feeding or is experiencing symptoms such as tummy pain or diarrhoea, see your GP. Don’t stop breastfeeding or giving your baby milk without seeing your GP first, as it’s important that your baby continues to get the nutrients he or she needs.
Further information
- British Nutrition Foundation
- Food Standards Agency
Sources
- Lactose intolerance. Food Standards Agency. www.eatwell.gov.uk, accessed 4 February 2010
- Lactose intolerance and the breastfed baby. Australian Breastfeeding Association. www.breastfeeding.asn.au, accessed 8 February 2009
- Lactose intolerance. British Nutrition Foundation. www.nutrition.org.uk, accessed 8 February 2010
- Simon C, Everitt H, van Dorp F. Oxford handbook of general practice. 3rd ed. Oxford: Oxford University Press, 2010:886-87
Can I drink soya milk if I have lactose intolerance?
Yes, as soya milk doesn’t naturally contain lactose.
Explanation
Although there is no medical cure for lactose intolerance, you can control your symptoms by reducing the amount of lactose in your diet. One way of doing this is by drinking soya milk instead of cows’, sheep’s or goats’ milk, as unlike these, it doesn’t contain any lactose.
Although you should limit the amount of lactose in your diet if you’re lactose intolerant, you may find you can still tolerate small amounts of cows’ milk, or are able to eat other dairy products such as cheese and yoghurt without experiencing any problems. This is because cheese contains much less lactose than milk and yoghurt seems to be easier to digest for people with lactose intolerance.
It’s important not to completely cut dairy products from your diet unless you’re very sensitive to lactose, as these foods are an important source of calcium. Calcium is important to keep your bones healthy. If you choose to drink soya milk as an alternative, it’s a good idea to choose one with added calcium.
Further information
- British Nutrition Foundation
- Food Standards Agency
Sources
- Lactose intolerance. Food Standards Agency. www.eatwell.gov.uk, accessed 4 February 2010
- Lactose intolerance. British Nutrition Foundation. www.nutrition.org.uk, accessed 8 February 2010
- Simon C, Everitt H, van Dorp F. Oxford handbook of general practice. 3rd ed. Oxford: Oxford University Press, 2010:886-87
- Food labels - reduced lactose or lactose free. Food Standards Agency. www.eatwell.gov.uk, accessed 8 February 2010
Related topics
Eczema
Food allergy
Gastroenteritis in children
This information was published by Bupa’s Health Information Team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.
Publication date: March 2010.
Lactose intolerance factsheet
Visit the lactose intolerance health factsheet for more information.
Related topics
Coeliac disease
Gastroenteritis in adults
Gastroenteritis in children
Healthy eating
Irritable bowel syndrome
Further information
- Food Standards Agency
- British Nutrition Foundation
Sources
- Lactose intolerance. Food Standards Agency. www.eatwell.gov.uk, accessed 3 December 2009
- Beers MH, Fletcher AJ, Porter R, et al. The Merck manual of medical information. New York: Pocket Books, 2003:735-36
- Lactose intolerance. Core charity. www.corecharity.org.uk, accessed 3 December 2009
- Lactose intolerance. British Nutrition Foundation. www.britishnutrition.org.uk, accessed 10 December 2009
- Reduced lactose or lactose free. Food Standards Agency. www.eatwell.gov.uk, accessed 3 December 2009
- Lactose intolerance. GP Notebook. www.gpnotebook.com, accessed 15 December 2009
- Calcium. Food Standards Agency. www.eatwell.gov.uk, accessed 15 December 2009
This information was published by Bupa’s Health Information Team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.
Publication date: March 2010.
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