Search element - Quick search bar

Lactose intolerance and the breastfed baby

There are lots of myths about lactose and breastfeeding


Lactose intolerance is poorly understood in the Australian community. There are lots of myths and misunderstandings about it, especially when it comes to babies. 

Contrary to what you may hear: 

  • Removing dairy from your diet makes no difference. There will not be less lactose in your breastmilk if you stop eating dairy products. 

  • There is no relationship between lactose intolerance in adult family members (including mum) and in babies. They are different types of lactose intolerance. 

  • A baby with symptoms of lactose intolerance should not be taken off the breast and fed on soy-based or special lactose-free infant formula. 

  • Lactose intolerance is very different to intolerance or allergy to cows' milk protein. 

Some facts about lactose 

Lactose is the sugar in all mammalian milks. It is produced in the breast. The amount of lactose in breastmilk isn’t related to the amount of lactose you consume and it hardly changes. The milk baby gets when they first start to feed contains about the same amount of lactose as the milk at the end of a breastfeed. However, the milk at the end does contain more fat. 

Lactase is the enzyme that is needed to digest lactose. Lactose intolerance occurs when a person does not produce this enzyme, or does not produce enough of it, and is therefore unable to digest lactose. If it isn’t digested and broken down, it can't be absorbed. If this happens, the lactose continues on in the digestive tract until it gets to the large bowel. It is here that bacteria break it down to make acids and gases. 

Lactose intolerance in babies 

Primary (or congenital) lactose intolerance:
This is an extremely rare genetic condition. The baby is born without any lactase enzymes. They fail to thrive from birth (ie not even start to gain weight) and show obvious symptoms of malabsorption and dehydration. This is a medical emergency and the baby would need a special diet from soon after birth. 

Secondary lactose intolerance: 
Because the enzyme lactase is produced in the very tips of the microscopic folds of the intestine, anything that damages the gut lining can cause secondary lactose intolerance. Even subtle damage to the gut may wipe off these tips and reduce the enzyme production, for example: 

  • gastroenteritis. 

  • food intolerance or allergy. In breastfed babies, this can come from food proteins, such as in cows' milk, wheat, soy or egg, or possibly other food chemicals that enter breastmilk from the mother's diet, as well as from food the baby has eaten. 

  • parasitic infection such as giardiasis or cryptosporidiosis. 

  • coeliac disease (intolerance to the gluten in wheat and some other grain products). 

  • following bowel surgery. 

The symptoms of lactose intolerance are liquid, sometimes green, frothy stools and an irritable baby who may pass wind often.

My baby has these symptoms. Do they have lactose intolerance? 

It can be difficult to know because these symptoms may also occur in a baby with other conditions.  

  • Lactose overload can look the same as lactose intolerance and is frequently mistaken for it. You may like to check the information on lactose overload to see if it matches what you see in your baby. Many mums find relief from their and their baby’s symptoms by addressing lactose overload first. 

  • Food allergies and food intolerances can cause a baby to be unsettled. The foods to which a baby is allergic or intolerant can pass through the mother's breastmilk. It can sometimes help for mum to remove the particular food, for example cows’ milk protein, from her diet. However, this needs guidance from a dietitian to help identify the problem foods and to make sure your diet is nutritionally adequate for both you and your baby. 

  • Cows' milk protein allergy (or intolerance) is often confused with lactose intolerance and many people think they are the same thing. They aren't. People probably get confused because cows' milk protein and lactose are both in the same food, that is dairy products. Since allergy or intolerance to a food protein can cause secondary lactose intolerance, the baby may have both. This adds to the confusion.  

Commonly asked questions about lactose intolerance

What about lactose intolerance tests?

A health practitioner may order a ‘hydrogen breath test’ or tests for ‘reducing sugars’ in the stool. If your baby is lactose intolerant, these tests would be expected to be positive. However, they are also positive in most normal breastfed babies under 3 months. Therefore, it is questionable whether they are useful.  

Can lactose intolerance be cured?

Secondary lactose intolerance is temporary, as long as the gut damage can heal. When the cause of the damage to the gut is removed, for example by taking the food to which a breastfed baby is allergic out of the mother's diet, the gut will heal, even if the baby is still fed breastmilk.  

If your doctor does diagnose 'lactose intolerance', continuing to breastfeed will not harm your baby as long as they are otherwise well and growing normally.  

If your baby has symptoms of lactose intolerance, you may be told to alternate breastfeeding with feeds of lactose-free formula or even take your baby off the breast. However, authorities only recommend the use of lactose-free formula if the baby is formula-fed and is very malnourished and/or losing weight. Human milk remains the best food for your baby and will assist with gut healing.  

In addition, you should consider the sensitivity of your baby to foreign protein (cow or soy) before introducing formula. Regular formula types, including lactose-free ones, may make this problem worse. You should seek professional advice on the need for hypoallergenic formula.  

A doctor should see any baby with long-term symptoms and/or who is failing to thrive. 

Should I stop breastfeeding?

Before you decide to pause breastfeeding, even partially, even for a short time, think about other aspects of the breastfeeding relationship.  

  • How will alternative feeding methods affect my baby? 

  • Could bottle-feeding other milk products result in breast refusal later? 

  • How easily will I be able to express my milk to maintain my supply? 

Average recovery time for the gut of a baby with severe gastroenteritis is 4 weeks but may be up to 8 weeks for a baby under 3 months. For older babies, over about 18 months, recovery may be as rapid as 1 week. If your doctor orders alternative feeds for your baby, remember that your breastmilk is still the normal and proper food for your baby in the long term.  

What about enzyme lactase drops?

You may have heard about giving drops containing the enzyme lactase to babies who have symptoms of lactose intolerance. There is little evidence that these are of much value when used this way, although there are anecdotal reports that relatively large doses may help in some cases.  

Lactase products are mainly designed to be added to expressed breastmilk (or other milk) and left overnight for the enzyme to predigest the lactose in the milk. In practice they seem to be occasionally useful for babies. While these products may help reduce symptoms, they do not solve the underlying issue of what is damaging baby’s gut. 

Lactose intolerance in adults 

Lactase enzyme levels normally change over a person's life span. They rise rapidly in the first week after birth, start to fall from about 3 to 5 years of age and fall sharply in later childhood. Low levels of lactose in colostrum are the same as the low levels of the enzyme present in the first week of life. 

Cows' milk is commonly consumed by adults in some populations, but mostly by people of northern European descent. In about 70% of the people of the world, and in a significant number of Australians, levels of this enzyme fall so low in adulthood that they become lactose intolerant. The tendency to adult lactose intolerance is genetically determined. People with Asian, African, Australian Aboriginal and Hispanic ancestry are more likely to be lactose intolerant as adults. Caucasians are more likely to be able to consume milk as adults because they tend to continue producing the enzyme lactase throughout life.  

An adult who has very low levels of the enzyme can usually tolerate some lactose because normal bacteria living in the gut are able to partially break it down. However, the person may find it gives them loose stools and 'wind'. 

Human babies of any ancestry can tolerate lactose. In fact, human milk has a very high concentration of lactose compared to cows' milk and that of other mammals. This is thought to be related to a human baby's rapid brain growth in infancy, compared to other mammals. Removing lactose from any baby's diet for more than a short period should not be done lightly and then only under medical supervision. 

It’s rare for a baby to have to stop breastfeeding 

As explained above, there are several types of lactose intolerance, but it is very rare for a baby to have to stop breastfeeding because of this condition. Except for the extremely rare primary type, there is always a cause behind lactose intolerance in babies. Getting to the cause and fixing that is the key to resolving the baby's symptoms. 


By Joy Anderson AM BSc(Nutrition), PostgradDipDiet, IBCLC, ABA Breastfeeding Counsellor  


© Australian Breastfeeding Association May 2022


Brodribb W (ed), 2012, Breastfeeding Management in Australia. 4th edn. Australian Breastfeeding Association, Melbourne.

Douglas PS 2013, Diagnosing gastro-oesophageal reflux disease or lactose intolerance in babies who cry a lot in the first few months overlooks feeding problems. Journal of Paediatrics and Child Health 49(4): E252–256.

Heyman MB for the Committee on Nutrition, 2006, Lactose intolerance in infants, children, and adolescents. Pediatrics 118(3): 1279-1286 (Available at

Lawlor-Smith C & Lawlor-Smith L, 1998, Lactose intolerance. Breastfeeding Review 6(1): 29-30.

Minchin M, 1986, Food for Thought. 2nd edn. Unwin Paperbacks, Sydney.

Rings EHHM et al, 1994, Lactose intolerance and lactase deficiency in children. Current Opinion in Pediatrics 6: 562-567.

Royal Australian College of Physicians 2006, Paediatric policy: Soy protein formula. RACP, Sydney.

Saarela T, Kokkonen J & Koivisto M, 2005, Macronutrient and energy contents of human milk fractions during the first six months of lactation. Acta Paediatrica 94: 1176-1181.

Vesa TH, Marteau P, Korpela R 2000, Lactose intolerance. Journal of the American College of Nutrition 19(2): 156S-175S.