Lactose intolerance

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What is lactose intolerance?
What causes lactose intolerance?
Common symptoms of lactose intolerance 
Diagnosing lactose intolerance
What can I do about my baby’s lactose intolerance?
Eating solids: lactose intolerance and diet
Lactose overload
Food allergy versus lactose intolerance

What is lactose intolerance?

Lactose intolerance occurs when the body can’t break down a sugar called lactose, which is present in all breastmilk, dairy milk and other dairy products.

Lactose makes up around 7% of breastmilk (and a similar amount in infant formula). Lactose provides around 40% of your baby’s energy needs, helps your baby absorb calcium and iron, and helps ensure healthy development.

Usually, the enzyme lactase, which is produced in the small intestine, changes the lactose into glucose and galactose — sugars which are more easily absorbed. Sometimes babies don’t produce enough lactase to break down all the lactose and the unabsorbed lactose passes through the gut without being digested. Undigested lactose irritates the gut and causes build up of wind and diarrhoea.

What causes lactose intolerance?

There are two types of lactose intolerance: primary and secondary.

Primary lactose intolerance occurs when babies are born with no lactase enzymes at all. This is extremely rare. It’s genetically carried and babies who have it need a special diet from the time they are born, in order to thrive.

Secondary lactose intolerance can occur if a child’s digestive system is disrupted by illness, affecting healthy production of enzymes like lactase, or if there is inadequate production of lactase.

Illnesses that might lead to secondary lactose intolerance include tummy bugs that cause gastroenteritis and coeliac disease. 

Gastroenteritis can cause temporary irritation to the lining of the stomach and small intestine, but this will usually clear up with time:

• for a baby aged under three months, around eight weeks
• for a baby older than 3 months, around four weeks
• for a baby 18 months and older, around one week.

Secondary lactose intolerance due to inadequate production of lactase most commonly develops after the age of three. Some people are more likely to develop it than others. For example, people from a Northern European background are generally less likely to develop it; Indigenous Australians and people from Asia or Africa are more likely to do so.

Sometimes lactose intolerance is confused with other digestive problems such as a food allergy or lactose overload. This is because these conditions have similar symptoms. Food allergies and lactose overload are not the same as lactose intolerance, and do not affect a baby’s production of lactase.

Common symptoms of lactose intolerance

Without lactase, the lactose in milk remains unabsorbed and stays in the intestines. As bacteria in the gut feast on the lactose, they produce large amounts of gas by fermentation. This causes a range of symptoms including:

• wind
• pain and swelling in the tummy
• irritability
• failure to settle
• at feeding times, coming on and off the breast
• failure to gain weight
• diarrhoea.

The diarrhoea occurs because unabsorbed lactose forces the intestines to retain excess water, causing frothy green diarrhoea.

Note: Lactose intolerance does not cause vomiting, but food allergies do.

Even if your child has these symptoms, it doesn’t mean he is lactose intolerant. Some or all of these symptoms are common in healthy breastfed infants, according to research. They can occur in the first week of life and last up to six weeks or as long as five months. It is also highly likely that the symptoms will disappear. As long as your baby’s weight and health aren’t suffering, it’s not likely that there is a problem.

Diagnosing lactose intolerance

Because the symptoms for lactose intolerance and food allergy are similar, clearly diagnosing lactose intolerance can sometimes be difficult.

Methods used to diagnose lactose intolerance include:

• Clinitest tablet — a small amount of faeces is mixed with water, than a special tablet is added and checked for colour change. This is commonly used when temporary lactose intolerance is suspected after gastroenteritis.
• Hydrogen breath test — this tests the amount of hydrogen gas in the child’s breath. Lactose intolerant children will have higher levels of hydrogen in their breath coming from the process of fermentation in the gut (bacteria feeding on lactose that has not been broken down).
• Elimination diet — this involves removing foods containing lactose from the child’s diet to see whether symptoms improve. If symptoms come back once the foods are reintroduced, then lactose intolerance is most likely the cause of the problem.

What can I do about my baby’s lactose intolerance?

The treatment for lactose intolerance in your baby depends to some extent on the cause. If your child has primary lactose intolerance, your doctor, paediatrician or nutritionist will help guide you.

For secondary lactose intolerance caused by gastroenteritis:

• Try using Lactaid drops that contain the enzyme lactase. (Note that there is some debate about the effectiveness of this treatment.)
• Alternate your baby’s breastfeeds with a lactose-free infant formula. If the situation is particularly serious, you may have to wean your baby onto the formula temporarily. If this occurs, keep expressing so that your supply of breastmilk is maintained.

If you are breastfeeding, persist if possible. Weaning is not recommended, because of the nutritional value of breastmilk and the benefits of lactose for your baby’s growth. Also, if your child can tolerate a small amount of lactose then gradually increasing lactose can help his body produce more lactase. 

And remember that one of the most important things you can do is soothe and comfort your baby when he’s showing symptoms.

Eating solids: lactose intolerance and diet

If your child is older and diagnosed with lactose intolerance, here are some tips for watching his diet. These also apply to adults with lactose intolerance.

Lactose overload

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

Lactose overload can occur when:

• Breastfed babies drink more first milk than last milk. The early milk passes through the digestive system faster than the last milk – so quickly, in fact, that there is not sufficient time for all of the lactose to be broken down.
• Bottle-fed babies drink a lot of milk.
• Mothers have a natural oversupply of breastmilk in their babies’ early weeks.
• Breastfed babies feed frequently and alternate breasts before the breasts have been emptied.
• Breastfed babies have a pattern of short breastfeeds – sometimes mothers (understandably!) shorten breastfeeds because of problems such as sore nipples or mastitis.
• Breastfed babies are not correctly attached to the breast, resulting in longer feeding times but less milk - so baby may be getting too much of the early milk.

Trying to slow down or lengthen the feed may help with lactose overload.

Read more about breastfeeding problems and solutions.

Food allergy versus lactose intolerance

Sometimes, symptoms we think indicate lactose intolerance are actually caused by a food allergy. An allergy to milk, for example, affects bottle-fed babies more than breastfed babies because the majority of infant formulas are based on cow's, goat's or soy milk.

It’s very rare for babies to be allergic to human breastmilk, although a protein allergy might develop from proteins eaten by a breastfeeding mother, which are then transferred into her breastmilk. An elimination diet can be used to diagnose such an allergy. This involves removing dairy foods such as milk, cheese, yogurt and cream from the mother’s diet. If the baby’s symptoms improve, but return when mum reintroduces the foods, this may suggest an allergy.

Reactions to food allergies are more severe than allergies to lactose intolerance. If your baby is allergic to food such as cow’s milk, soy products or egg, you may notice the following symptoms:

• vomiting
• blood or mucus in his diarrhoea
• poor weight gain
• wheezing or asthma.

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