What is lactose intolerance?

Lactose intolerance is when the gut can’t break down lactose. This problem happens because there isn’t enough lactase in the small intestine.

Lactose is a sugar present in all breastmilk, dairy milk and other dairy products. It makes up 5-7% of breastmilk, infant formula and dairy products.

Lactase is an enzyme. Enzymes break down the nutrients in food so the body can use them.

Lactose is important for your baby’s health and development. It provides around 40% of your baby’s energy needs and helps them absorb calcium and iron.

Causes of lactose intolerance

There are 3 main causes of lactose intolerance.

Lactase non-persistence (hypolactasia)
This happens when your child’s lactase enzymes gradually start to decrease. This is genetic and very common – about 70% of people have this type of lactose intolerance. Symptoms can start after the age of 5 years, but they’re usually more noticeable in teenagers and young adults. Children can usually still tolerate small amounts of lactose in their daily diets.

Congenital lactase deficiency (alactasia)
This happens when babies are born with no lactase enzymes at all. This is genetic and extremely rare. Babies with this kind of lactose intolerance have severe diarrhoea from the first day of life and fail to thrive. They need a special diet from the time they’re born so they can grow and develop well.

Secondary lactose intolerance
This can happen if a child’s digestive system is upset by infections like gastroenteritis, which can temporarily damage the lining of the stomach and small intestine. This kind of lactose intolerance is short term and usually improves after a few weeks.

Conditions like coeliac disease can also lead to secondary lactose intolerance. Once these conditions are being managed properly, lactose intolerance should be less of a problem.

Common symptoms of lactose intolerance

Symptoms of lactose intolerance in babies, children and teenagers include:

• wind
• stomach pain and bloating
• diarrhoea
• rumbling tummy.

Babies with lactose intolerance might also have symptoms like:

• nappy rash
• crankiness or irritability
• trouble settling
• attachment problems during breastfeeding
• failure to gain weight.

Even if your baby has these symptoms, it doesn’t always mean that they’re lactose intolerant. Some or all of these symptoms can be common in healthy breastfed infants.

If you think your baby or child has the symptoms of lactose intolerance, you should talk with your GP.

Sometimes lactose intolerance is confused with food allergies. Food allergies involve your immune system, but food intolerances don’t. Also, common food allergy symptoms include vomiting, blood or mucus in poo, hives and facial swelling – these aren’t symptoms of lactose intolerance. If your child has symptoms like these, see your GP.

Assessment and diagnosis of lactose intolerance

These are the 2 main tests that your doctor might recommend if your child has symptoms of lactose intolerance.

Hydrogen breath test
For this test, your child drinks a standard amount of lactose. Then the amount of hydrogen gas in your child’s breath is measured. Lactose-intolerant children have higher levels of hydrogen in their breath.

Elimination diet
This involves removing foods containing lactose from your child’s diet to see whether symptoms improve. If the symptoms come back once the foods with lactose are reintroduced, lactose intolerance is most likely the cause of the problem.

It’s best to speak to your GP or a dietitian before starting your child on an elimination diet. They’ll ensure that your child’s diet continues to give your child the nutrition they need for growth and development, even while you’re eliminating things from it.

Treatment: lactose intolerance in babies

The treatment for lactose intolerance in babies often depends on the cause. And no matter what’s causing your baby’s lactose intolerance, it’s important to soothe and comfort your baby when they’re showing symptoms.

Congenital lactase deficiency
If your baby has congenital lactase deficiency, your GP, paediatrician or dietitian will guide your child’s treatment.

Secondary lactose intolerance
For a breastfed baby with secondary lactose intolerance caused by gastroenteritis, you should be able to keep breastfeeding.

Weaning off breastmilk isn’t usually recommended. This is because breastmilk has so many nutritional benefits and lactose is good for your baby’s growth. Your child can usually tolerate a small amount of lactose, and gradually increasing it can help your child’s body produce more lactase.

If your baby is formula fed or you’re considering giving them formula, consult your GP or a dietitian before using or changing to a low-lactose or lactose-free infant formula. If your child is under 6 months, avoid using soy-based infant formula.

Talk to your GP if you’re thinking of using Lacteeze drops in expressed breastmilk or Lacteeze tablets. There’s some debate about the effectiveness of these treatments. Also talk to your GP if you want to try replacing breastmilk or alternating breastmilk with formula, or you’re generally worried about your baby’s nutrition.

Treatment and management: lactose intolerance in older children and teenagers

If your older or teenage child is diagnosed with lactose intolerance, you can reduce the amount of lactose in their diet. But you don’t need to get rid of products with lactose completely, especially if your child eats only small amounts of them with other foods during the day.

Your child can usually eat:

• cheeses with very low lactose content – brie, camembert, cheddar, colby, edam, fetta, gouda, havarti, mozzarella, parmesan, halloumi, Swiss and Tilstat
• yoghurt – the bacteria in yoghurt breaks down the lactose so it’s usually fine for your child to eat
• calcium-fortified soy products – soy yoghurt, soy milk, soy ice-cream and soy cheese
• lactose-free cow’s milk
• butter and cream – these contain only small amounts of lactose and are usually fine to eat
• bread, cereals, fruit, vegetables, meat and other protein foods
• full-fat milk – the fat in full-fat milk gives your child’s body longer to digest lactose.

Your child should be careful about eating:

• milk ice-cream and milk desserts
• cream cheese, processed cheese and cheese spread
• muesli bars
• instant mashed potato and vegetables with added milk or white sauces.

You or your child should check the ingredients in:

• biscuits, cakes and cake mixes
• soups
• mayonnaise
• milk chocolate.

Lactose overload in babies

Lactose overload isn’t the same as lactose intolerance – that is, it isn’t a problem with the production of lactase. Rather, lactose overload happens when a baby consumes large amounts of lactose at one time and can’t break it all down.

Lactose overload can happen when mothers have a natural oversupply of breastmilk in their baby’s early weeks. It can also happen when breastfed babies switch to the second breast before the first breast has been well drained.

And it can happen when bottle-fed babies drink a lot of milk, but this isn’t common.

If your baby has symptoms of lactose overload, check your breastfeeding position and breastfeeding technique. Good attachment can help your baby drain the first breast before moving to the second. If over-feeding is causing the overload, try not to feed more often than every 3 hours.