Making sense of lactose intolerance in babies

From Nestlè Infant Formula Guide:
“Lactose-free or soy-based formulas are important for babies with a clinically proven allergy or food intolerance…”

My previous article on breastfeeding addressed the attitudes surrounding the breast vs bottle debate. As I have mentioned before, even though there is still room for improvement, breastfeeding initiation rates are not bad in most Western countries. However, the rates drop sharply by 6 months with mothers quoting different reasons for early weaning, lactose intolerance being one of the major ones.

This post is going to be quite “sciency” so I’m going to get serious and attempt to keep sarcasm to a minimum.

Self-diagnosis of lactose intolerance in both adults and babies is very common. Before drawing any conclusions let’s look at some science involved. Lactose is a disaccharide which means it is made up of two single sugar molecules: glucose and galactose. Only these  monosaccharides  can be absorbed through our intestine which is why mammals possess an enzyme lactase which does the job.

Lactase is one of the brush border enzymes located on the surface of our small intestine where the digestion of lactose takes place.

Microvilli house enzymes on their surface

Several types of lactase deficiency have been described.

1. Congenital lactase deficiency – this is an extremely rare genetic condition where the body makes no lactase at all. This condition is normally diagnosed in the first week of life, often even before the baby leaves the hospital due to extreme failure to thrive. These babies require intensive follow up by paediatric gastroenterologists.

2. Late onset lactose intolerance – lactase levels gradually diminish from the age of 2-7. In Asian and African populations almost 90% of people show lactose intolerance due to very low levels of this enzyme. On the other hand Northern Europeans continue to have higher levels through adulthood with only 5% considered lactose intolerant. Other populations seem to be somewhere in between with differences between individuals depending on the genetic makeup. However, even in adults, the ability to tolerate dairy also depends on the overall health of your gut. Viruses, unhealthy gut bacteria and chronic inflammation from some foods can all cause the symptoms of lactose intolerance which can be reversed. More on that later.

3. Acquired lactose intolerance in infancy – this is what I will be talking about here. I find that the lack of understanding and the myths surrounding this condition are far and wide and should concern every parent. Two major mechanisms for acquired lactose intolerance are fast intestinal transit and mucosal inflammation.

First thing you have to know is that lactose is the sugar unique to mammalian milk. Every baby needs lactose for a very specific reason. Apart from providing about 40% of energy, lactose contains galactose, a monosaccharide essential to brain development. Galactose is incorporated into glycolipids (galactolipids) and glycoproteins in the cells throughout the body and especially in the central nervous system. We are still learning the exact mechanisms and the role of galactolipids but it is obvious that depriving a growing brain of some of its building blocks might not be a good idea. Human breast milk contains the highest concentration of lactose among all mammals. This is the main reason why evolution gave us lactase.

The problem with lactase (if you can call it a problem) is that it has a slow release time in the small intestine, regardless of total quantity of lactose in a meal. This means that anything that increases the intestinal transit time also compromises the digestion of lactose. So when it comes to the digestion of milk, the slow and steady tortoise literally wins the race. If the bolus of food moves too fast there isn’t enough lactase to break down the lactose in the meal and it swooshes past into the colon. There is no lactase in the colon but there is plenty of bacteria. Happy to receive an unexpected source of energy, bacteria use fermentation to process lactose with by-products like acids and gases. The results of this lethal cocktail are quite unpleasant, whether you are a baby or an adult: bloating, diarrhoea, acidic stool causing “nappy rash” and abdominal pain.

So what causes the fast transit of the food through the intestines? Lower fat and higher carbohydrate concentration of the meal are the common culprits. If you are an adult, it’s simple enough: skim latte will send you running to the loo faster than a full-fat one. If you are a breastfed baby though your milk supply depends on the mother. Breast milk is higher is carbohydrates at the beginning of the feed with fat content gradually increasing by the end of the feed. Taking a baby off the breast too soon will result in a lower-fat feed. Therefore breastfeeding women are recommended to empty one breast completely  before offering the other.

Another reason for lower-fat breast milk is the mother’s own diet. High carbohydrate low-fat diet during lactation changes the composition of the breast  milk to similarly higher-carb lower-fat. Our ancestors knew this and nursing mothers in traditional societies were encouraged to eat plenty of high quality animal fats to support the growth of the infant. However, in our times ancient wisdom gives way to the cult of thin. So first they tell you that you need to  lose all that pregnancy blubber pronto. Then they inform you that the best way  to lose weight and stay healthy is to reduce saturated fat in your diet. Skim  milk and reduced fat yoghurt are conveniently provided. And by the way, did you  know that Gwyneth Paltrow follows a macrobiotic diet (and doesn’t she look like  one sexy lollipop?) so why don’t you reduce your consumption of animal products  as well? What’s that? Your baby has colic? She must be lactose intolerant: here  is a tin of soy formula.


Let’s move on to the second common reason of transient lactose intolerance:  mucosal inflammation. The inside (mucosal) surface of the small intestine is very fragile, especially in babies, and can be easily damaged. Minor viral infections affecting the gut (viral gastroenteritis) can temporarily reduce  lactase concentration and cause the typical symptoms of lactose intolerance. Luckily, intestinal mucosa heals very rapidly and the damage will be completely  repaired in a few weeks. In the meantime, it is recommended that the mother keeps breastfeeding,  as it will speed up the healing time and prevent “nipple  confusion”.

A more serious cause of mucosal damage is chronic inflammation due to a  food allergy/intolerance. In addition to the typical symptoms of lactose intolerance, the baby might also show the signs and symptoms of inappropriate immune system activation (atopy): eczema/other skin complaints and asthma (rarely diagnosed in babies under 12 months old). In the context of exclusive breastfeeding, casein (one of milk proteins) is often seen as the main offender. However, the levels of casein in human breast milk are actually quite low, compared to cow’s milk, and casein allergy is a lot more common in formula-fed babies. In addition, babies that do develop casein allergy also tend to get allergic to soy protein as well. Therefore switching to soy formula rarely solves the problem. And brings a host of its own issues: phytoestrogens and aluminum toxicity among others.

The baby may also develop an intolerance to the food consumed by the mother, typically wheat, soy, milk proteins and others. If mucosal damage due to protein intolerance is suspected, the only way to  treat it is to remove the offending agent from the mother’s diet, not to remove breast milk. If the symptoms appear after the introduction of solids, then every opportunity should be taken to remove wheat and soy proteins from baby’s food. If there is a history of allergies, atopy, eczema or asthma in the family it is the strongest argument yet to breastfeed and continue to do for as long as possible. Numerous studies show that breastfeeding provides strong protection against atopy in childhood and later in adulthood.

OK, I know that was a lot to take in. For the parents out there: I hope this has made some sense and dispelled some of the myths surrounding lactose intolerance. For the adults: same principles of lactose intolerance apply. Both fast intestinal transit time and intestinal damage reduce your tolerance to dairy. Only we have less enzyme to play with.

Important points:
 1. Lactose is vital for baby’s nervous system development
2. Every baby is born with enough lactase enzyme to adequately process breast milk (congenital lactase deficiency excepted)
  3. Lactose intolerance is a transient phenomenon in infants and breastfeeding should not be interrupted except in the most severe cases.
  4. Both intestinal transit time and mucosal damage are the main factors in individual dairy tolerance in all age groups.
5. The mother’s diet can cause LI: inadequate dietary fat (especially from animal products), consumption of wheat, soybean and occasionally milk proteins.
6. Breastfeeding provides the best protection against developing allergies in infancy and later in life.

ABA article, Lactose Intolerance and the Breastfed Baby
Johns Hopkins Medical Institutions (2011, May 1). Formula-fed preemies at higher risk for dangerous GI condition than babies who get donor milk. ScienceDaily. Retrieved June 26, 2011, from­ /releases/2011/04/110430171122.htm
Noble R, Bovey A, Resolution of lactose intolerance and colic in breastfed babies,
presented at the ALCA Vic (Melbourne) Conference on the 1st November, 1997
Concerns for the use of soy-based formula in infant nutrition. Paediatr Child Helath 2009 Feb 14(2): 109-113
Osborn DA, Sinn JKH. Formulas containing hydrolysed protein for prevention of allergy and food intolerance in infants. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD003664. DOI: 10.1002/14651858.CD003664.pub3

23 thoughts on “Making sense of lactose intolerance in babies

  1. Now you have my attention…brilliant…..lolipops are the answer!!!!!.It just makes sense……..great read Anastasia……Those intestines are ugly little suckers…….

  2. The essentiality of galactose to the development of the CNS is a stunning new (to me) fact. Makes me wonder about my brother. Mom was told he was “allergic to her milk” and formula was started shortly after he was born. He developed schizophrenia in his late teens.

    • Hi Jen, sorry to hear about your brother. It’s hard to draw conclusions and even harder to try to guess “what if”. The best thing you can do now is help him with the best nutrition possible, minimize inflammation via eliminating industrial seed oils, wheat and reducing fructose. Have you seen Dr Emily Dean’s blog? She is a psychiatrist with an interest in paleo nutrition. She has a series on schizophrenia and diet (www.

      • Thanks, Anastasia — your suggestions are excellent, as is your blog, and Emily’s as well. Keep writing, both of you!

  3. I found out a long time ago, through trial and error, that my body did not handle low fat milk products well (and non fat were just horrible). Thanks for the reason why! I have 5 kids, all at a very healthy weight, who get whole fat milk products (one is still BF, so I love these posts). Thanks for posting.
    Another Mom from the US

    • Hi Joanne, you are right, sometimes it’s best to listen to your body rather than go with nonsensical nutritional guidelines. Congratulations on your 5(!) healthy children.

  4. I found that understanding the lactose issue was key to optimal breastfeeding for both my girls – when they were very young, I had to restrict their feeding to one side at a time, or they would be gassy and uncomfortable and poop all the time (even more than usual for a newborn 😉 ) I never heard that advice from the pediatricians or nurses – I read it somewhere online. But it was truly miraculous when they would sleep longer and the tummy distress went away, from one simple change in how I fed them.

    Oh, and thanks for the plug for my blog in your comments! 🙂

    • No problem, happy to plug :). Re lactose: I find it frustrating that the knee-jerk reaction to any colic issues is to switch to formula, often soy-based (shudder!).

  5. Thank you for this! You explained this all very clearly. I’ve had many friends who had issues with foremilk/hindmilk imbalance, causing their babies to be gassy and fussy with nasty stool and bad diaper rashes, and now I understand how that works. My own two-year-old daughter, who still nurses very enthusiastically, has food intolerances that resulted in me having to cut a lot of stuff out of my own diet. That process led in a roundabout way to taking on a primal lifestyle.

    Off to share this on FB… 🙂

    • Thanks Kristin. It’s amazing how often having children results in a different outlook on health and nutrition. Congratulations on successful breastfeeding and on improving your own diet.

  6. Interesting read Anastasia! Any idea if an assumed lactose intolerance in a baby and an attempt to fix the problem, introducing soy or whatever can lead to the child having a stretched bowel or loss of elasticity in the bowel ( can’t remember how it was worded exactly, re my nephew who is now 6 yrs old and on a gluten and lactose free diet) Suz 🙂

    • Hi Suz, not sure what a stretched bowel would be referring to. Did they tell you the exact diagnosis? Without knowing the specifics: there are two possibilities. Your nephew might have been born with a congenital problem in his bowel which manifested itself similarly to lactose intolerance. Or not having the probiotic benefits of breastfeeding might have caused or contributed to the problems he is having now. I think that gluten free diet has an opportunity to be very healthy: lots of good animals products and vegetables/fruit providing proteins, fats and vitamins essential for growth. Unfortunately it can also lose its way when parents unable to imagine a child’s life without cakes, crumpets, biscuits and spaghetti bolognese, choose very highly processed fake gluten-free substitutes.
      Regarding lactose, unless your nephew was born with congenital lactase deficiency which I described in the post, he is unlikely to have a full-blown lactose intolerance. Babies with lactose intolerance tend to grow out of it by the age of 12-18 months. If he doesn’t tolerate dairy products, this could be due to gut damage or casein allergy. I think dairy is important for children and growth however if it is impossible then other sources of nutrients need to be provided (and no, soy is not a good substitute).
      Sorry can’t give any definite information but like I said there is no reason why your nephew can’t have a healthy natural diet. It might be even better than most other people.

  7. Another thing to note is that there are different types of casein, and the one that most casein-allergic people are allergic to is not the kind found in human milk (or goat milk for that matter… or it may be in very low levels in goat milk, can’t quite recall!).

    • poppy, cows milk is deficient in many nutrients that breast milk provides and it also has much higher levels of casein. Babies digestive systems are more “leaky” and this is the reason why they can develop a cows milk allergy if it is given too early. Normally 12 months marks the time when the gut is mature enough to take in cows milk.

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  9. Wow. I just found your blog after googling ‘Picasso breastfeeding print’ as I was looking for a print I had seen at the art gallery years ago!!! But I am so glad I ended up here.. as a nutritionist and a breastfeeding-advocate I am really glad I read this article.

  10. I have a 6 wk old that is super fussy. He basically cries whenever hes awake. He doesn’t sleep much and it very hard to get to sleep. Often he wakes up 30mins later just to start the routine all over again. We feel there just has up be something wrong! We have a miserable bbaby! After i called the oed and asked if the baby could have an allergy, the pediatrician rec’d going on a dairy free diet to see if it helps. I opted to go soy free too just because I read half of babies with dairy intolerance have soy too. I just didn’t want to risk him being miserable after removing dairy just to learn it should have eliminated soy too.
    So it’s been four day and we see little ( but some) improvement. Could it be something else? Is there anything I should do? Help!

    • Betsey, sorry to hear your bub is being unsettled. I’m afraid this is a case of being absolutely impossible to make a diagnosis over the Internet as there are too many variables. I hope this turns out to be temporary and you guys get through this trying time.

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