What is lactose intolerance?

Lactose intolerance is when you can’t break down lactose. Lactose is the main sugar found in milk made by mammals. Lactose can be found in:

• milk including evaporated milk, milk powder, condensed milk
• yoghurt
• ice cream
• soft cheeses
• buttermilk
• other dairy products made from milk

It’s sometimes referred to as dairy intolerance and is rarely serious.

Lactose intolerance is different from milk allergy.

Milk allergy

Milk allergy is an immune reaction to cow’s milk protein.

Milk allergy can be:

• mild
• moderate
• serious

Mild milk allergy can cause:

• itchy skin
• rash

Severe milk allergy can cause:

• swelling or tightness in your throat
• difficulty breathing

Get urgent medical advice if you suspect a serious allergic reaction. A serious allergic reaction is a medical emergency.

Milk allergy isn’t the same as lactose intolerance.

What are the symptoms of lactose intolerance?

The symptoms of lactose intolerance are:

• wind (farting)
• bloating
• abdominal pain and cramps
• nausea
• diarrhoea, or needing the toilet urgently

The symptoms usually come on 30 minutes to a few hours after eating or drinking products containing lactose. Drinking just 1 cup of milk can cause symptoms.

Symptoms of lactose intolerance are often dose related — the more you eat the worse they get.

What causes lactose intolerance?

Lactose is a natural sugar found in dairy foods. Lactose is normally broken down by an enzyme called lactase. Lactase is made in your small intestine.

Lactose intolerance happens when your body does not produce enough lactase.

Instead, the unabsorbed lactose moves into your large intestine. Here it’s digested by bacteria using their own enzymes. The gases created in this process can produce symptoms.

Most people can break down lactose when they're born. However, it’s normal for there to be less lactase activity as you age.

There are other factors that may also increase your risk of developing lactose intolerance.

Genetic factors

Lactose intolerance is often due to genetic factors. You are more likely to be lactose intolerant if you are:

• East Asian
• West African
• Middle Eastern
• Southern European — Greek and Italian
• Aboriginal and Torres Strait Islander

Other causes of lactose intolerance

Lactose intolerance can also be caused by medical issues, such as:

• gastroenteritis — which strips your intestines of lactase for a week or 2
• a parasitic infection — which can lower your lactase levels
• coeliac disease — the lactose intolerance should improve with a gluten free diet
• Crohn’s disease — especially if you have inflammation or surgery to your small intestine

When should I see my doctor?

If you think you might have lactose intolerance, it’s important to see your doctor.

How is lactose intolerance diagnosed?

Lactose intolerance is usually tested for by a lactose challenge. This is where you see what happens when you have a large amount of lactose. For example, drinking a milkshake.

Your doctor may suggest that you trial a lactose-free diet. During this time, you will have to monitor what happens with your symptoms. If your symptoms improve, but return when you reintroduce lactose, then you probably have lactose intolerance.

Other tests are sometimes available in private laboratories and hospital clinics. These include the following.

• Hydrogen breath test — measures hydrogen in your breath before and after a dose of lactose.
• Blood glucose test — this is done multiple times after taking a dose of lactose.
• Lactose intolerance genetic test — looks for 4 genetic variations that control how much lactase you make.
• Small bowel biopsy — a sample of your bowel wall is taken during an endoscopy (when a camera is passed into your intestines). A biopsy is an invasive test, so it isn’t often used.

However, none of these tests will prove that you are lactose intolerant.

How is lactose intolerance treated?

The main treatment for lactose intolerance is to lower the amount of lactose in your diet. You won’t have to remove all lactose from your diet. The amount of lactose you can tolerate will vary from person to person.

It’s a good idea to visit an accredited practising dietitian. They can help you lower the lactose in your diet and still get enough calcium.

Many dairy foods don’t contain large amounts of lactose and are a good source of calcium.

Lactose intolerance can be temporary. It’s possible to slowly reintroduce milk and other dairy products over time.

If your symptoms don’t improve with a lactose-limited diet, you should speak with your doctor or dietitian.

Lactose intolerance and a low FODMAP diet

If you are lactose intolerant and also suffer from irritable bowel syndrome (IBS), you may follow a low FODMAP diet.

Visit this site to find out more about lactose and dairy products on a low FODMAP diet.

Lactose intolerance and medicines

A few people have such bad lactose intolerance that they must not take certain medicines because they contain lactose. It’s best to speak with your doctor or pharmacist if this is the case for you.

Tips to help manage your lactose intolerance

You may also need to change how you eat dairy foods to lower your chance of symptoms.

Build up your tolerance by starting small and slowly increasing your milk consumption. Most people with lactose intolerance can tolerate ½ cup of milk at a time.

Other things to try:

• drink milk in small quantities
• eat lactose-containing foods with other foods
• choose regular fat milk as it has less lactose than low-fat or skim milk
• hard cheeses are low in lactose and are usually well tolerated
• yoghurt is also often well tolerated as it contains bacteria that break down lactose

You can buy enzyme tablets and drops from your pharmacy. Taking these before eating lactose containing foods will help stop your symptoms.

Be careful to check the labels of processed foods such as:

• biscuits
• cakes
• cheese sauce
• cream soups
• custards

Look for the terms:

• ‘milk solids’
• ‘non-fat milk solids’
• ‘whey’
• ‘milk sugar’

However, lactose is only likely to be a problem if these terms are either of the first 2 ingredients listed.

Tips to get enough calcium

It’s important to still eat enough calcium. Most adults need at least 1,000 mg of calcium every day — more if you are older or a pregnant woman.

Soy products with added calcium don’t contain lactose and can replace dairy products.

Other foods that are good sources of calcium are:

• calcium-fortified foods
• tinned fish with bones, such as salmon and sardines
• nuts and seeds
• broccoli and other leafy green vegetables
• rhubarb

Complications of lactose intolerance

Eating lactose may cause unpleasant symptoms but it won’t damage your bowel (large intestine). There are no long-term complications of lactose intolerance.

Resources and support

If you suspect you have lactose intolerance, it’s wise to speak to a doctor or dietitian. You can find an Accredited Practising Dietitian on the Dietitians Australia website.

For more information about lactose intolerance you can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with 24 hours a day, 7 days a week.