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HealthInfo Waitaha Canterbury

Lactose intolerance

Lactose is a natural sugar found in milk and some milk products such as yoghurt and ice cream. An enzyme called lactase usually breaks down lactose in your small intestine. Lactose intolerance happens when your small intestine doesn't 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:

These symptoms usually begin 30 minutes to two hours after eating or drinking lactose-rich foods.

Lactose intolerance is not common in pēpi (babies). Most lactose intolerance starts during childhood or the teenage years.

It's more common in Asian, Middle Eastern, Mediterranean, South American and African people. It may also be more common in Māori and Pasifika people.

People sometimes get lactose intolerance after gastroenteritis (tummy bug). It 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.

Milk allergies

Lactose intolerance is not the same as a milk allergy.

A milk allergy is an allergic reaction to the protein in milk and is more common in pēpi babies and young tamariki (children) than adults. It usually disappears as tamariki grow older.

If you have a milk allergy, you need to avoid all animal milk and milk products. If you have a lactose intolerance, you can usually eat cheese and small amounts of milk and yoghurt.

Diagnosing lactose intolerance

If you think you might be lactose intolerant, talk to your GP or practice nurse. They will ask you about your symptoms and your health and lifestyle.

If it's possible that you're lactose intolerant, you'll need to avoid lactose-rich foods for two weeks to check if your symptoms go away.

Lactose-rich foods include:

  • fresh cow, goat and sheep milk
  • powdered, evaporated, and long-life milk
  • buttermilk
  • sweetened condensed milk
  • yoghurt
  • 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 will not 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 do not get better after two weeks, then you aren't lactose intolerant. You should start eating normally again and see your GP.

If your symptoms get much better after two weeks, then you know lactose is a problem.

On the next page: Self-care for lactose intolerance

Written by HealthInfo clinical advisers. Last reviewed December 2021.


Page reference: 250023

Review key: HILAC-250023