What is lactose intolerance?

Lactose intolerance is when your body can't break down lactose. Lactose is the main type of sugar found in milk made by mammals. Cows and goats are examples of mammals that make milk used by people.

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 called dairy intolerance. Most of the time it is not serious.

If you have lactose intolerance it is different from having cow's milk allergy.

Milk allergy

Milk allergy is an immune reaction to proteins that are found in cow's milk.

Mild milk allergy can cause itchy skin and a rash.

Severe or serious milk allergy can cause:

• swelling or tightness in your throat
• difficulty breathing
• vomiting

What symptoms are related to lactose intolerance?

The symptoms of lactose intolerance are:

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

The symptoms usually happen soon after you eat or drink products containing lactose. Drinking just 1 cup of milk can cause symptoms.

Symptoms of lactose intolerance will depend on how much of the milk or dairy product you eat. The more you eat the worse the symptoms get.

Lactose intolerance symptoms in babies and children

Babies and children can have lactose intolerance. They might have:

• wind
• stomach pain
• tummy rumbling
• diarrhoea
• nappy rash

Some babies with lactose intolerance can be slow to put on weight. They might have trouble settling or seem irritable or upset. This is because the symptoms of lactose intolerance make them feel sick.

There can be other reasons for all these symptoms. It's best to take your child to the doctor if you think they might have lactose intolerance or if you are worried.

What causes lactose intolerance?

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

Your digestive system (gut) has many parts. Different foods are broken down at different stages as they go through your gut. Food goes into your stomach, then through your small intestine then your large intestine. Foods containing lactose are usually broken down in your small intestine.

Lactose intolerance happens when your small intestine does not make enough lactase.

If you do not have enough lactase, lactose moves into your large intestine. Here it is digested by your gut bacteria. When these gut bacteria break down lactose they make gas. This gas gives the symptoms of lactose intolerance. These symptoms can be things like wind or stomach pain.

Most people can break down lactose . However, it's normal for you to make less lactase as you age.

There are some other reasons that may increase your chance of getting lactose intolerance.

Genetic factors

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

• 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 two
• a parasitic infection in your small intestine, which can lower your lactase levels
• coeliac disease — lactose intolerance should improve with a gluten free diet
• Crohn's disease — especially if you have inflammation or an operation on your small intestine

How is lactose intolerance diagnosed?

Your doctor will ask about your diet and your symptoms. There are several tests for lactose intolerance. They might suggest you do a lactose challenge. This is where you see what happens when you eat or drink something with a large amount of lactose. For example, drinking a milkshake.

Your doctor may ask you to see what happens if you follow a lactose-free diet for a while. During this time, you will have to notice if your symptoms get better or worse. If your symptoms get worse when you start eating or drinking lactose again, you might have lactose intolerance.

There are other tests that can be requested by your doctor. 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 a few times after taking a dose of lactose.
• Lactose intolerance genetic test
• 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.

When should I see my doctor?

If you think you might have lactose intolerance, it's important to see your doctor or a dietitian for advice.

How is lactose intolerance treated?

Self-care at home

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 cope with varies from person to person. Removing all lactose is not necessary - you just need to find the amount of dairy products that do not cause you symptoms. For some people this means they can still drink small amounts of milk several times per day.

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 vitamin B12 from your food to stay healthy.

Not all dairy foods contain large amounts of lactose. Hard cheese and yoghurt close to the expiry date don't contain much lactose.

Lactose intolerance can be a short-term problem. It's possible to slowly take in more 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.

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

Medicines for lactose intolerance

You can buy enzyme tablets and drops from your pharmacy. You can stop symptoms from happening if you take these tablets or drops before eating foods with lactose.

Other treatment options and tips to help manage your lactose intolerance

Build up your tolerance to lactose by slowly increasing the amount of milk you drink. Most people with lactose intolerance can cope with about half a cup of milk at a time.

You can try:

• drinking milk in small quantities at a time
• to choose regular fat milk - it has less lactose than low-fat or skim milk
• eating small portions of hard cheeses — these are low in lactose and do not usually cause symptoms
• eating yoghurt — it doesn't usually cause symptoms as it contains bacteria that break down lactose.

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

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

Look for the words:

• 'milk solids'
• 'non-fat milk solids'
• 'whey'
• 'milk sugar'

The foods that contain 'milk solids' are most likely to cause symptoms of lactose intolerance.

How to manage lactose intolerance in babies or children

Breastfed babies with lactose intolerance can still have breast milk. Speak to your doctor or child health nurse about breastfeeding. The doctor or nurse can also advise you about the best baby formula to use. Do not give lactose free formula to a baby with cow's milk protein allergy.

Older children should have a diet lower in lactose. They can still eat many dairy foods such as yoghurt and most cheeses. Foods to avoid can include ice cream and cheese spreads. Speak to your doctor about what foods they should eat. Your doctor might suggest taking them to a dietitian.

Complications of lactose intolerance

If you have lactose intolerance, eating foods with lactose may cause unpleasant symptoms. These are short-term and only happen after having food or drink that contains lactose. It is important to know that eating and drinking these foods won't damage your bowel (large intestine). There are no long-term complications of lactose intolerance.

Calcium

If you reduce the amount of dairy foods you eat you might worry about how much calcium you are getting. 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

Can lactose intolerance be prevented?

Nowadays there are plenty of lactose-free or dairy-free options. If you're lactose intolerant you can prevent symptoms by changing what you eat and drink.

Resources and support

Go to eatforhealth.gov.au for information about dairy foods and their alternatives.

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.

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

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