Is your baby unsettled or having trouble sleeping because of lactose intolerance or overload?
This page belongs to collection of short articles and videos in plain language, called When baby cries a lot in the first few months of life. Together, these articles and videos will give you a brief and simple summary of the Possums 5-domain approach to the crying baby. For comprehensive information on this topic, please consider reading The discontented little baby book. If your baby is formula fed, please go straight to the last two sections of this page. Please seek the help of your local GP or NDC Accredited Practitioner if you have concerns about your baby's health and wellbeing.
Why is the lactose in your breast milk so important?
Lactose is the most hardworking ingredient in your milk. There's nothing complicated about the lactose molecule, but it is essential for the growth and development of your baby’s body and brain.
Lactose is not only your milk's main source of nutrient for your baby, it's the ingredient in your milk which regulates your milk volume and also the stability of your milk's composition.
Lactose is broken down into glucose and galactose by an enzyme, lactase, which is found in your baby's small intestine. Usually, all or most of the lactose is broken down in your baby's small intestine and absorbed directly from the small intestine to fuel her body and brain, with very little undigested lactose making it into your baby's large intestine or stool.
Does your breastfed baby have lactose overload?
Sometimes when a woman has a very generous supply of milk relative to her baby's physiological needs, so much lactose floods through her baby's small intestine that it isn't properly digested by the lactase, and undigested lactose reaches the colon. Any undigested lactose which reaches your baby's colon feeds certain bacteria which live in the microbiome of baby's colon. These bacteria ferment the lactose.
This can result in what we call lactose overload in an otherwise well and healthy breastfed baby, which, when severe, makes babies cry. Lactose overload is rarely a problem in a breastfed baby after the first couple of months of life.
Lactose overload is a spectrum condition. Many newborns and young babies have a touch of lactose overload, but their mother doesn't need to change anything that she is doing with breastfeeding, and it settles down quickly. However, at the upper end of the spectrum, lactose overload is the one condition in (otherwise well) breastfed babies which might cause gut pain, resulting in unsettled behaviour. You can find out more about gut pain and unsettled baby behaviour here.
If your baby is experiencing the upper end of the spectrum of lactose overload, he'll show some or all of the following signs. Your baby might
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Dial up, or cry a lot
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Pass large amounts of flatulence very frequently
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Pass frothy, explosive, copious stools
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Have a tight, swollen abdomen because of gas in the large intestine. (Babies' tummies are always tight when they are dialled up, but this bloatedness is apparent even when your baby isn't crying. If this is severe or you have concerns about your baby's health and wellbeing, please see your GP.)
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Feed a lot for comfort, because he has gut pain and discomfort
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Gain weight rapidly, often crossing up onto a higher percentile line on the World Health Organisation's percentile chart for weight.
Green stool and mucous in the stool are normal for breastfed (and non-breastfed) babies, and are not signs of lactose overload in a breastfed baby. The lactose overload of breastfed babies is often misdiagnosed as allergy. It's also sometimes misdiagnosed as reflux or gut dysbiosis.
It's not uncommon for a mother with a crying baby who has a lactose overload to be told to space out breastfeeds. However, spacing out breastfeeds not only makes baby's crying worse, it can quickly decrease that mother's breast milk supply.
What can you do when your breastfed baby has a lactose overload?
You can stop your baby's lactose overload by changing the way you offer the breast. You allow one breast to run full, as you return your baby to feed from the other breast over a period of time.
If you let your breasts run full, your milk supply dials down. As your supply dials down, it will better match your baby's needs, and is better handled by your baby's small intestine, so that the fermenting in the large intestine settles down. It takes two or three days for this to work.
Returning your baby to the one breast over a period of time before offering the other needs to be done carefully, because two things can go wrong.
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You might develop a mastitis if your breast runs too full
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You might drop your supply to less than your baby needs, if you do this for too long.
I don't use the term 'block feeding', because feeding from the one breast over a set block of time can lead to either mastitis or low supply. Only you can judge when your other breast is becoming full enough, so that it's time to let your baby feed from that full side.
Just a few days of letting one breast, then the other, run full is usually enough, depending on your situation. It takes a couple of days for any change you make in the way you offer your breasts to result in changes in your baby's behaviour.
Does your baby need to take more cream from your milk?
The higher the volume of milk in your milk glands, the lower the proportion of fat or cream that is released into that portion of your milk. As your baby's feed progresses, and the amount of milk being released by each letdown decreases, the concentration of fat or lipids in that portion of milk increases.
Lactose levels are very stable in breast milk, and also the amount of cream a baby takes from her mother's breasts over a 24-hour period is stable too. The changing proportion of fat relative to lactose in your milk is not something you need to worry about as a breastfeeding woman, because this self-regulates. Your baby will get the cream that she needs, if she is taking the lactose that she needs.
But there are misunderstandings about how this changing proportion of fats works in breastfeeding. For instance
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Sometimes you might hear it said that the first part of your milk is sugary or weak or not strong enough. This isn’t true! You don’t need to be trying to get the creamy portion of milk into your baby, because the fat content in your baby’s breastfeeds looks after itself. But your baby definitely needs lots of lactose! Lactose is your milk's powerhouse of nutrition!
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Sometimes you might hear it said that you need to let your baby 'drain the breast' to get lots of cream. This isn't true either, and can accidentally cause
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Your supply to never build properly if you're doing this when your baby is a newborn, or
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Your supply to decrease so that it no longer meets your baby's needs.
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Are there circumstances when a breastfed baby needs to be put onto lactose-reduced or lactose free formula?
Sometimes, a breastfed baby develops a gastroenteritis. The virus or bacteria which causes the gastroenteritis might damage the lining of the gut, and temporarily interferes with the secretion of lactase in baby's small intestine.
However, in these situations, breast milk remains very rich in protective and healing factors, and is the best possible medicine for the gut of a little one who has or has had a gastrointestinal infection, even if the small intestine lining is very damaged by the infection. Breastfeeding helps heal the gut injury caused by an infection. The best thing to do for your baby is to continue breastfeeding as usual, even though your baby's gut may continue to show the signs of lactose overload for a time after the gastroenteritis has passed.
Occasionally, a breastfed baby develops a true food protein allergy, which also disrupts lactase secretion in the small intestine. You can read about breastfeeding and true allergy (and also why allergy is often overdiagnosed and overtreated in babies) here.
Most rarely of all, a baby might be born with a congenital lactase deficiency, which is life-threatening and an emergency. This baby needs urgent medical management with lactose-free feeds (which unfortunately excludes your breast milk), from birth.
Will lactase drops help when your baby is unsettled?
No, the research shows that lactase drops don't help babies who cry and fuss a lot. This is not surprising, given that there is no problem with lactase production or its action in the gut of an unsettled baby.
When might lactose be a problem if your baby is formula-fed?
Lactose overload is a breastfeeding management problem, and doesn't occur in babies who are fully or partly fed with formula.
Lactose intolerance may occur if your formula fed baby has
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Severe gastroenteritis, or a
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True allergy or food protein induced enteropathy syndrome.
Temporary lactose intolerance develops in these two situations because the lining to your baby's small intestine becomes damaged, so that the lactase enzyme is not secreted as much as the baby needs to digest the lactose from his formula in the small intestine. The lactose then passes into the colon and ferments, causing frequent copious stools and gas production.
This damage to the lining of the small intestine is usually temporary, and will resolve in a short period of time after the cow's milk lactose has been removed from your baby's diet. In a case of true allergy or food protein induced enteropathy syndrome in a formula fed baby, your doctors will advise you on formula management. Standard lactose free formulas still contain cow's milk proteins.
If your baby is receiving some breast milk, your doctor may advise substituting your usual formula with a reduced lactose formula. But lactose intolerance is not a reason to stop giving your baby whatever breast milk you can, because of the wonderfully protective and healing effects of your breast milk.
Recommended resources
Harriet's four-week-old breastfed baby Jamie cries a lot from lactose overload
Lactose: your breastmilk and your baby depend upon it
The difference between lactose malabsorption, lactose intolerance, and lactose overload
Selected references
Forsgard RA. Lactose digestion in humans: intestinal lactase appears to be constitutive whereas the colonic microbiome is adaptable. American Journal of Clinical Nutrition. 2019;110:273-279.
Kozlowska-Jalowska A, Strozyk A, Horvath A. Effect of lactase supplementation on infant colic: systematic review of randomized controlled trials. Journal of Pediatric Gastroenterology and Nutrition. 2023;78:1009–1016.
Kent JC, Gardner H, Lai C-T, Hartmann PE, Murray K, Rea A, et al. Hourly breast expression to estimate the rate of synthesis of milk and fat. Nutrients. 2018;10:1144.
Kent JC, Mitoulas LR, Cregan MD, Ramsay DT, Doherty DA, Hartmann PE. Volume and frequency of breastfeedings and fat content of breast milk throughout the day. Pediatics. 2006;117(3):e387-395.
Misselwitz B, Butter M, Verbeke K, Fox MR. Update on lactose malabsorption and intolerance: pathogenesis, diagnosis and clinical management. Gut. 2019;68:2080-2091.
Nau AL, Bassan AS, Cezar AB. Lactase for infantile colic: a systematic review of randomized clinical trials. Journal of Pediatric Gastroenterology and Nutrition. 2024;79:855-862.
Toca M dC, Fernandez A, Orsi M, Tabacco O, Vinderola G. Lactose intolerance: myths and facts. An update. Archivos Argentinos de Pediatria. 2022;120(1):59-66.
Vaz SR, Tofoli MH, Avelino MAG, Da Costa PSS. Probiotics for infantile colic: is there evidence beyond doubt? A meta-analysis and systeamtic review. Acta Paediatrica. 2023;113:170-182.