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Lactose intolerance
Lactose is a natural sugar found in milk and some milk
products such as yoghurt and ice cream. Lactose is usually
broken down in your small intestine by an enzyme called
lactase. Lactose intolerance happens when your small
intestine does not make enough lactase.
When this happens, the lactose passes through to your
large bowel. The bacteria that live in your large bowel
break down the lactose. This causes symptoms such as:
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nausea (feeling sick)
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bloating (tight or swollen tummy)
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wind
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tummy cramps
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diarrhoea (the runs).
These symptoms usually begin 30 minutes to two hours
after eating or drinking foods that contain lactose.
Lactose intolerance is not the same as milk allergy
Milk allergy is an allergic reaction to the protein in milk, and is more common in babies and
young children than adults. It usually disappears as children grow older.
If you have a milk allergy, you need to avoid all milk and milk products. If you have a lactose
intolerance, you can usually eat cheese, and small amounts of milk and yoghurt.
How common is lactose intolerance?
Lactose intolerance is not common in babies. Most lactose intolerance starts during childhood or
the teenage years. It is more common in Asian, Middle Eastern, Mediterranean, South American
and African people. It may also be more common in Māori and Pacific people.
People sometimes get lactose intolerance after gastroenteritis (tummy bug). This can also happen
due to damage to the small intestine caused by diseases such as coeliac disease. This type of
lactose intolerance usually disappears once the infection or disease has been treated.
HealthInfo reference: 250023
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Issued: 2 August 2016
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Page 1 of 2
Lactose intolerance
www.healthinfo.org.nz
Diagnosing lactose intolerance
If you think you might be lactose intolerant, talk to your doctor or practice nurse. They will ask
you about your symptoms and your health and lifestyle. If it's possible that you are lactose
intolerant, you will need to avoid lactose-rich foods for two weeks.
Lactose-rich foods include:
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fresh cow, goat and sheep milk
powdered, evaporated, and long-life milk
buttermilk
sweetened condensed milk
yoghurt
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custard
ice cream
creamy pasta sauces and white sauces
sour cream and crème fraîche
soft unripened cheeses such as ricotta,
cottage, cream cheese, and mascarpone.
You don’t need to avoid bread, biscuits or cake that contain milk. The amount of milk in these
foods is not enough to cause symptoms.
If your symptoms don’t get better after two weeks, then you are not lactose intolerant. You
should start eating normally again and see your doctor.
If your symptoms get much better after two weeks, then you know lactose is a problem.
Lactose intolerance can also be diagnosed by breath hydrogen testing.
Breath testing is not available in the public health system in Canterbury, but you may opt to
pay for it privately. You can search for a company that does breath testing in the Yellow pages.
Go to the Yellow pages online and search for “Dietary specialists”.
Written by HealthInfo clinical advisers. Endorsed by Nutrition and Dietetics, Christchurch Hospital. Updated
August 2016.
Image courtesy of stockimages at FreeDigitalPhotos.net.
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HealthInfo reference: 250023
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Issued: 2 August 2016
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Page 2 of 2