Key points
  • Lactose intolerance is a condition where your body can’t digest lactose properly. This can lead to unpleasant symptoms like bloating, gas, cramps and diarrhoea.
  • Lactose is a naturally occurring sugar found in dairy foods. It is normally digested by an enzyme called lactase. Some people do not produce enough of this enzyme to break down the lactose in food. These people are lactose intolerant.
  • You don't need to eliminate all lactose-containing foods from your diet. These foods are important sources of nutrients. Instead, understand which foods and quantities you can tolerate.
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What is lactose intolerance?

Lactose intolerance is a set of symptoms caused by the body’s inability to digest lactose properly.

Lactose is a naturally occurring sugar found in dairy foods. It is broken down or digested by an enzyme in our body called lactase and ends up in the bloodstream as glucose (another type of sugar).

People with lactose intolerance either don’t have enough of the lactase enzyme to properly digest the lactose sugar, or they might have inflammation of the gut which causes temporary lactose intolerance. The undigested lactose sugar travels in the digestive tract to the large intestine where it attracts water and is fermented by the gut bacteria that live there. The undigested lactose may cause symptoms including:

  • Diarrhoea
  • Stomach cramps
  • Bloating
  • Excessive flatulence

These symptoms can be related to many other conditions. It’s a good idea to discuss your symptoms with a GP before reducing or removing lactose from your diet.

Causes of lactose intolerance

Lactose intolerance is often due to genetic factors. People with East Asian, West African, Middle Eastern, Greek, Italian, and Aboriginal and Torres Strait Islander backgrounds often produce less lactase enzyme and have a 70-95% chance of being lactose intolerant. In Caucasians, approximately 1 in 20 people have some degree of lactose intolerance.

Other causes include:

  • Gastroenteritis - which can reduce the amount of lactase enzyme you produce for several weeks after you’re unwell
  • Parasites - which can temporarily reduce your levels of the lactase enzyme, leaving you unable to break down lactose
  • Intestinal inflammation – untreated Coeliac disease and other gastrointestinal conditions that cause inflammation of the intestinal lining can make it difficult for lactase enzyme to work effectively.

Diagnosis

Lactose intolerance can be diagnosed in several ways. The easiest is by assessing what happens when you ingest a large amount of lactose. If you drink a milkshake and have significant symptoms afterwards, you may have a lactose intolerance.

If you’re not sure if lactose is the trigger and have been confused by your response in the past, then you should speak with your GP or a dietitian who can help you work out what is going on.

Your doctor many suggest a hydrogen breath test to detect lactose intolerance, and if you’re scheduled for a gastroscopy or colonoscopy, your gastroenterologist can measure the lactase enzyme levels in your gut.

A genetic test can also be used to diagnose lactose intolerance, but keep in mind there is an out-of-pocket cost to have this test done.

It’s important to note that these tests are not conclusive and should be interpreted by your doctor, considering symptoms and your diet.

Management

It is not necessary to remove all dairy products from your diet. People with lactose intolerance still produce a small amount of the lactase enzyme.

The amount of lactose a person can tolerate varies, for example, you may tolerate a small amount of milk in a cup of tea but not a milkshake.

Recent evidence suggests you should try and continue to eat as much lactose as you can tolerate. Complete avoidance of lactose may make your body produce even less of the lactase enzyme and become more sensitive.

Tips for managing lactose intolerance

  • Drink milk in smaller quantities. Most people with lactose intolerance can tolerate ½ cup milk at a time. Full cream milk can be better tolerated than low fat or calcium-enriched milk.
  • Spread lactose-containing foods out during the day. Eat them with other foods to slow down digestion.
  • Yoghurt is lower in lactose as the natural bacteria break it down. It is generally well tolerated by people with lactose intolerance.
  • Hard cheeses (such as cheddar) are very low in lactose and again well tolerated.
  • You can buy lactose-free milk, yoghurt, ice cream and soft cheeses. These are produced by adding lactase enzyme to the products to break down lactose for you.
  • You can buy enzyme drops or tablets from the pharmacy. Add them to regular milk and other dairy products to make it easier to digest.
  • Lactose can also be an ingredient in many processed foods such as biscuits and cakes, cheese sauce, cream soups and custards. Check the ingredient list for things like milk solids, non-fat milk solids, whey and milk sugar. However, it is only likely to be a problem if it is a major ingredient (that is, one of the first two ingredients listed).
  • Soy milk and oat milk do not contain any lactose and can be suitable substitutes for dairy products, providing they have calcium added (check the ingredients list on the packaging for the word ‘calcium’). Find out more about plant-based milks. 

 

Woman buys dairy products in the supermarket
When to see a dietitian

We recommend seeing a dietitian if you:

  • are struggling with any of the symptoms of lactose intolerance
  • have been diagnosed with lactose intolerance and want some support on dietary management of this condition
  • want to better understand how to meet your nutrient requirements while limiting your intake of lactose to reduce symptoms
  • want to know the best dietary approach to minimise symptoms and discomfort
  • would like a personalised eating plan to address a lactose intolerance

Accredited Practising Dietitians (APDs) are university-trained nutrition experts. They can help you with personalised, easy-to-follow and evidence-based advice.

APDs are Australia's most trusted dietetics professionals.

Find a dietitian

Top tips
  • See a GP or dietitian if you’re suffering from the common symptoms of lactose intolerance. They can help confirm lactose intolerance and give you advice to reduce symptoms and discomfort.
  • If you're lactose intolerant, you don't need to eliminate lactose-containing foods entirely. These are important sources of calcium and other nutrients. Learn which foods and in which quantities you can tolerate without triggering symptoms.
  • There are plenty of lactose-free or dairy-free options, which provide alternative sources of nutrients if you're lactose intolerant
This health advice page was peer-reviewed by an Accredited Practising Dietitian (APD) in February 2022.