Lactose intolerance in babies: Here’s what new mums need to know

There are lots of myths and misunderstandings about lactose intolerance and breastfed babies. This article by midwife and lactation consultant, Bel Moore, intends to shed light on what exactly a lactose intolerance is, as well as the relevant and related signs and symptoms.

Baby bottle with milk on a green sheet
Source: Istock.

What is lactose intolerance?

Lactase is an enzyme that the body uses to digest lactose (the sugar found in milk and milk products). It turns this sugar into glucose and galactose, which are more easily absorbed.

If the body does not produce enough lactase, undigested lactose gets into the large bowel and bacteria feast on the undigested lactose, resulting in build up of gas, wind pains and diarrhoea.

Lactose is present in breast milk (making up about 7 per cent), cows milk formula, cow’s milk and other dairy products.

Types of lactose intolerance

Congenital lactose intolerance is a very rare inherited metabolic disorder where a baby is born with no lactase enzymes at all. They become very sick in the first week of life, will not grow well until lactose is removed from their diet and require a specialised lactose-free formula.

Primary lactose intolerance (also called developmental, late-onset or adult lactose intolerance) is a gradual decrease in the body’s production of lactase (needed to break down lactose) and is relatively common in adults (but never appears before 2-5 years of age).

Premature babies may have a temporary form of lactose intolerance (developmental lactose deficiency) because their bodies are not yet producing lactase, but this will go away as baby and gut matures.

Preemie Feeding
Source: Istock.

Secondary lactose intolerance

Secondary lactose intolerance (or acquired lactose intolerance) can appear at any age and occurs when there is a reduction in lactase activity due to damage (infectious, allergic or inflammatory process) to the intestinal brush border.

Causes of secondary lactose intolerance can include:

  • Gastroenteritis
  • Bowel infection
  • Parasite
  • Intolerance or allergy
  • Coeliac or Crohn’s disease
  • Bowel surgery

Symptoms of secondary lactose intolerance ( caused by the bacteria in the gut eating the lactose) are:

  • Green frothy/very liquid bowel motions
  • Irritability (i.e. sleeps little, cries a lot)
  • Excessive gas or ‘windy’
  • Pain and swelling in the tummy
  • Coming on and off the breast during breastfeeding
  • Failure to gain weight
  • Red or raw nappy rash caused by acidic poo

Knowing the difference in symptoms 

Some or all of these symptoms are common in healthy breastfed infants from time to time and don’t necessarily mean that they are lactose intolerant.

It’s highly likely the symptoms will disappear and as long as your baby’s weight and health aren’t suffering, it’s not likely there’s a problem.

It’s always wise to consult your GP, Child Health Nurse or an IBCLC about any issues or concerns you may have in regards to feeding and growth (especially if your child has diarrhoea and under three months old).

Lactose overload

Confusingly, many of the symptoms of secondary lactose intolerance are the same for infants suffering from lactose overload.

Lactose overload is where a breastfed baby is getting too much lactose in the breastmilk.

The level of lactose in a mother’s breastmilk is not determined by the mother’s diet.  Lactose overload can make a baby uncomfortable with the above symptoms but they still get all the nutrition they need from the breastmilk.

Lactose overload is usually associated with a mother having an oversupply and the baby being under 3 months of age.

The oversupply causes a large-volume, but lower-fat feed to go through the baby quickly, leaving the lactose very undigested when reaching the lower bowel.

The fermenting lactose in the bowel produces gas and acid stools causing the baby to have tummy pains and the baby will usually ‘act hungry’ (wants to suck, unsettled, draws up his legs, screams – mothers often think they actually have low supply due to this! But it’s usually because sucking gives them comfort and pain relief).

If you suspect you have over supply, contact your local IBCLC to talk about possible reasons for your oversupply and solutions such as blockfeeding.

Cows milk protein intolerance (CMPI)

As the CMPI symptoms are similar to lactose intolerance/overload they are often misdiagnosed or confused.

Source: Istock.

Cow’s milk protein intolerance (CMPI) is an abnormal reaction by the immune system to a protein found in cow’s milk and affects around 2 per cent (1 in 50) of Australian and New Zealand infants.

There are two types of Cow’s Milk Protein Intolerance:

  • IgE-mediated (immediate reaction- within 2 hrs). Symptoms:  hives, rashes, wheezing and a runny nose instead or additional to the gastro intestinal issues
  • Non-IgE mediated (delayed reaction- 48 hours to a week).GI issues such as:
    • Vomiting
    • Blood and/or mucus in stool
    • Diarrhoea
    • Poor weight gain
    • Eczema

Cow’s milk protein can be found in breast milk only if the mother consumes products containing cow’s milk.

Therefore the mother can eliminate cow’s milk protein by avoiding cow’s milk and products containing it (reduction/cessation of symptoms when on an elimination diet will usually lead to diagnosis).

This is where The Healthy Mummy smoothie comes in handy. The Healthy Mummy Smoothie mix is 100 per cent gluten and dairy free.

Pineapple & Passionfruit Smoothie

It’s loaded with 24 vitamins and minerals, protein, carbohydrates, fibre and healthy fats, providing a nutrient hit for mums. The smoothie is also breastfeeding friendly and contains fenugreek (which has been known to help increase breast milk supply).

You can download our smoothie fact sheet and get a full list of smoothie ingredients here.

Most babies and children who are intolerant of cows milk will usually be intolerant of soy and therefore it should be avoided as well (if symptoms do not resolve with just eliminating cows milk).

Almost 75 per cent of CMPI children with have resolution by 3 years of age and can be trialled on cow’s milk products.

See your GP/ paeditrician and/or dietician before removing any products from your diet and for further advice on allergies.

Related information

For information on Dairy Free & Lactose Free Alternatives click here.

You can also check out Healthy Mummy Community member, Natalie’s story, about how she continued to breastfeed despite her baby’s intolerance.


Read Natalie’s journey here.


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