Are babies born lactose intolerant?

A vegan friend of mine at work with whom I also have interesting debates insists that babies are born lactose intolerant, and that it’s only by repeated doses that we “teach” their bodies to accept it. This doesn’t sound likely, but if it is, are there any side-effects to forcing a baby to eat something “unnatural” like this? And why hasn’t there been a bigger fuss about it? How diffirent is human milk that cow milk (obviously there are some diffirences).

People that are not lactose-intolerant make an enzyme (lactase, I believe it’s called) that breaks down lactose, or milk sugar. The lactose-intolerant, like myself, do not make this enzyme, or they make very little of it. Babies are not naturally born lactose-intolerant, and digesting lactose is not something your body “learns”. My last baby was born lactose-intolerant, and the way we knew was he would scream alot and his poop was hard and obviously painful for him. There’s a chance a baby can outgrow this, I think, and by the time they can drink milk, at 1 year, they may be able to tolerate it. My son, now 5, is still lactose-intolerant. Babies under 1, by the way, should not drink milk because they need the full-spectrum nutrition that formula provides as their diet is quite limited, but regular (non-soy) formulas are milk-based. I’ve had a vegan try to convince me that non-pasteurized, non-homogenized milk is easily tolerated by the lactose-intolerant, but I’m quite sure that’s bull.

No, no, no. Absolutely not.

All mammals are genetically programming to be able to survive exclusively on their mother’s milk until the age of weaning. And all mammal’s milk (with a couple of not important to the discussion exceptions) contains lactose as its sole sugar, one of the sources of energy.

So all mammals produce the lactase enzyme from birth to be able to digest the lactose in their mother’s milk.

This holds true for humans as well.

A very tiny number (perhaps less than 100) of cases are known in which babies were born with no lactase-making ability. If these babies are not immediately identified and placed on a substitute formula they will die of starvation, as they all presumably did before the first such case was identified in the 1950s. They never outgrow this. I can only assume that trublmakr has made the common error of confusing this with cow’s milk protein allergy, which many infants do outgrow.

To go on to answer the inevitable next question:

Lactase production normally stops at about the age of weaning, approximately three years of age for humans, although the individual variation is immense. The gene that a small percentage - perhaps 3-5% - of humans are born with contains a mutation that fails to send out that stop signal. This is the archetypal example of a natural, neutral mutation. There is not the slightest indication that being able to produce lactase all one’s life has any effect on the body whatsoever. For most of the existence of humanity it was a hidden and meaningless mutation.

But in an example of environmental change, in this case the social environment, humans began to domesticate a variety of animals whose milk could be harvested. In the fullness of time, the ability to be able to drink milk, a good source of calcium and other nutrients, provided a reproductive edge, especially in the north of Europe where other good calcium sources were hard to find.

It is a historical accident that those northern Europeans spread their genes and their dairy culture around the world so that the inability to use dairy products would cause minorities in some nations to be looked upon as freakish rather than the global norm.

Therefore the mutation that allows milk-drinking as an adult is the most important mutation known to exist, and it follows the current understanding of the evolutionary process natural selection spreading a trait contrived through a neutral mutation across a population perfectly. It should be noted and cited in GD on a regular basis.

Still, how could even a vegan think that mother’s milk could possibly be unnatural in any conceivable way? And human milk is the highest in lactose among all the mammals’ milks. And lactose is totally unaffected by homogenization and pasteurization so doing that or not doing that to milk makes not a particle of difference.

This site has an exhaustive comparison of human and cow’s milks.

Steve Carper’s site has more information on lactose intolerance than any other single site. His book, Milk Is Not for Every Body: Living With Lactose Intolerance has a long chapter on the history of lactose intolerance.

Obviously, I’m not an expert on lactose-intolerance, but I’m pretty sure when my son was a baby he didn’t have a milk allergy, he was lactose-intolerant. And he has been since. Being intolerant myself since about age 16, I’m very aware of the signs and symptoms, and he is definitely not allergic, but intolerant. Are you saying that there have only been 100 or so documented cases of this at all, ever? Just wanted to clarify.

Actually the number documented in the medical journals is more like 40, but I added some because now that doctors know what to look for more are being found.

The condition is called congenital lactose intolerance. It is definitely permanent.

Is it possible that your son was premature?

The symptoms of milk allergy in infants are often very similar to those of lactose intolerance, and can only be told apart by a diagnostic test.

Part of the problem is that “lactose intolerance” is commonly misused to mean “milk doesn’t agree with me”. But there are several ways that milk can be a problem. Yes, most people stop producing lactase as they get older, and therefore lactose is undigested in their small intestine, but broken down by bacteria in their large intestine, resulting in diarhea, gas, and whatnot. This is lactose intolerance.

But people can also be allergic to the proteins in milk. And giving cow’s milk to babies is a very bad idea since cow’s milk has a different composition than human milk. Cows milk has more protein, more fat, and lower sugar, and the proteins are different than human milk proteins. Babies definately have a hard time digesting cows milk. Most kids shouldn’t drink cows milk until after they have started on solid foods.

Some babies have a hard time with milk based formula…my nephew was colicky and cranky until my brother switched him to soy formula. But I’ve never heard of this happening with breast milk, except for the very very rare condition Exapno cited.

But to go back to the OP, the idea that human babies are “lactose intolerant” is simply hogwash. The main source of calories in breast milk is lactose. If babies were lactose intolerant they would starve to death if they were fed only breast milk. Once again, human breast milk contains mostly lactose. Your friend is seriously confused.

But yes, it is certainly true that human babies shouldn’t drink cows milk until they are starting on solid food, and it is certainly true that human babies have absolutely no need for cows milk in their diet. But it is not true that repeated exposure to cows milk will increase a child’s tolerance for cows milk. They will either continue to produce lactase, or they will eventually stop producing it, and this is controlled by genetics. In most of the world lactase production starts to slow down around 3-5, and by adulthood have completely stopped producing the enzyme. Exposure to milk has nothing to do with it. But some people have a mutation that allows them to continue lactase production into adulthood. And we find this mutation is much more common in cultures that have a history of dairying.

Just another nail in the coffin of the credibility of your friend.

Normal human fetuses should be born with lactase enzyme. However, as Exapno, mentioned, it doesn’t start to develop until the 30th week in utero, so premature babies may lack it.

Is you friend by chance a porpoise or dolphin? They are the only mammalian species I know of without lactose in their milk. All other mammalian babies can, most decidedly, digest lactose.

Close, but not quite right.

The mammals that do not produce lactose are the Pinnipedia, the suborder that includes seals, sea lions, and walruses. They have such high fat contents in their milks - in the neighborhood of 35% - that no additional sugar energy is needed. This is obviously an adaptation to their life in extremely cold waters, something not normally an issue for porpoises and dolphins.

Technically, the monotremes and marsupials should also be included. While all of them do produce some lactose in their milks, it is on the order of a trace to 1%, and not the primary sugar.

Just to follow up Lemur866, the American Academy of Pediatrics discourages the use of cow’s milk for babies under one year of age. Properly fortified cow’s milk or soy milk formulas are the best alternatives to breastfeeding. However, historically speaking, the milk of whatever the local milkable animal was has been used in all places over the last several thousand years as a substitute feed when the mother or a wet nurse was not available. Milk of any animal is by far the best natural substitute for breastmilk.

Well, it might not be due to any relationship to water temperature (this I don’t know about), but dolphins only have a trace of lactose. My one source says “practically no lactose” and another source said at most 1% (similar to what you noted among marsupials).

So you’re saying that dolphins are marsupials? :dubious:

This may be an issue of different species of dolphin having very different characteristics. I can find your sources on the Internet, but also this Lactation Biology course table that appears to be used at more than one college. (Also at

In any case, even some lactose requires lactase, and that makes all the difference physiologically.

(And the comparison to the marsupials doesn’t work, since they have other sugar sources in their milk to give them a total high carbohydrate count that dolphins do not. Don’t make me go through Comparative Physiology: Primitive Mammals again or I’ll show you cranky.)


Sorry, I wasn’t clear; I didn’t mean to compare them to marsupials in any other way than to glom onto the same #, the “1%” figure for lactose.

I was going off of what I read in “Milk, Money & Madness: The politics and economics of breastfeeding” The authors said sea mammals were the exception to the lactose rule, and mentioned dolphins and porpoises specificially. However, it seems you’ve got data from some poor bastard zoologist who has actually milked these things, so I certainly defer to your information. LOL

It’s got to be the oddest thing I’ve ever been in a nitpick about.

Yes, I knew that. I was being facetious. I really can quote from Olav T. Oftedal’s table of primitive mammal milk in that volume, though. I can also clear out a room in twelve seconds flat. :slight_smile:

:eek: Do you really mean this, or were you specifically referring to cow’s (i.e. non-human) milk?

In context, the sentence you ripped that fragment from clearly refers to the difference between cow’s milk and cow’s milk-based formulas. I can’t find any confusion there.

Lactose intolerance is the new vegetarianism.

Many babies are grumpy in the evenings the first few weeks or months of their lives; in its most severe form this is called colic. Nobody knows why this happens, but parents who are formula feeding their babies will often be advised by friends and family to switch formulas until the baby settles down. Breastfeeding mothers, meanwhile, will get advice to stop eating this or that because it “doesn’t agree with the baby”. There is no evidence that any of this helps[li], but it happens that around the time they’ve decided to switch to a soy or “lactose free” formula, or Mamma has eliminated dairy from her diet, the baby calms down. The baby was going to calm down anyway, just because s/he has matured a bit and doesn’t get the evening grumpies any more, but it’s likely to get credited to the change in diet - the baby must be lactose intolerant![/li]
If there’s an actual medical reason for those lactose-free formulas to be so widely available in the States, I’d like to hear it…

Well, okay, there’s some controversy about whether cow’s milk proteins could cross into breastmilk, but let’s not make this more complicated than need be, okay?

Not entirely true. There are other herding cultures, some of which also drink lactase-containing foods. Its not only a Northern European thing.

Okay, there’s a gray zone in the middle here that some people have probably missed. Lactose overload. This DOES happen a lot in babies, especially ones with food allergies (such as to cow milk protiens), but it is a secondary reaction, not a primary one. It is technically called “Secondary Lactose Intolerance” (that is, it is secondary to another condition, not a primary condition of the person’s).

Lactose overload is a catch-all for any reason that lactose ends up in the large intestine, where the body is NOT expecting it to be. Lactose overload has the same symptoms as lactose intolerance, because in lactose intolerance, the lactose is not digested for lack of the enzyme, and in lactose overload, it is not digested (or not digested enough), for any one or more of multiple other reasons.

I find the lactose intolerance diagnosis for trublmakr interesting, because lactose intolerance typically causes diarrhea, not constipation. Too much lactose in the lower gut causes the body to dump fluids to the intestine to thin it out (plus the bacteria in there go nuts on it, causing a lot of gas), and ta-da! Diarrhea. Constipation in reaction is a new one for me. Not saying it isn’t possible, but I’ve never heard of it before. (Any cites on that from anyone?)

Lactose overload in babies does happen. Sometimes it is due to food issues, like milk allergy. Sometimes it is due to milk oversupply (maternal), which causes baby to consume more of the lactose-rich foremilk without much of the fat-rich hindmilk - and without the fats, the digestion processes too fast. The enzymes don’t have enough time/contact to break down all the lactose, and some of it gets to the lower gut, causing diarrhea and painful gas. Milk allergy does the same thing by damaging the brush border (inner surface) of the upper small intestine, where lactase is produced, thereby again reducing the capacity of the gut to digest lactose, and again letting it get to the lower gut intact. Oversupply is probably the most commonly misdiagnosed breastfeeding condition, and as noted, often moms are told to stop eating this or that, and all of a sudden, baby is better - only it isn’t gut maturity that does it, it is lactation maturity (supply settling down to match demand). Easy to interpret it the wrong way, because in people who don’t change what they’re doing and just muddle through, yep, indeed, it gets better. Must be the baby’s maturity changing, because mom’s milk doesn’t change, right? Quality assumption, just not necessarily accurate (gut maturity plays a big role if they’re premature, though).

BTDT with the lactose overload thing. Typically, women produce about 30% more milk for a second (+) baby than for their first (with women who produced the least with their first having the greatest increase). If your supply was decent the first time, and you aren’t also nursing a toddler at the same time, chances of you having at least a temporary oversupply when your milk production is still somewhat driven by hormones (2 weeks to 3 months postpartum, in most of the women I know), are pretty decent. I had the fun of having an oversupply for 6 months. On top of that, my son had a dairy allergy (multi-systemic, so a full allergy, not just ‘sensitive’, which tends to show up in one system only - I drank milk, he got rash, hives, vomitting, congestion, and diarrhea). Thin green jelly-like stuff that disappears into the diaper like water isn’t normal baby poop, just in case you wondered.

[hijack that flodnak warned of](oh, and flodnak, until you mentioned it, I hadn’t heard ANY controversy over whether cow’s milk protien passes into breastmilk… and none of my medical cites seems to have any problem with the idea - they treat it as a medical fact that it does. However, once you mentioned it, I had to check, and I found research saying it might be secondary factors relating to the mother consuming cow milk protien and those factors getting into breastmilk as a secondary process, and THOSE compounds causing the allergic symptoms. Or that low levels of maternal cow-milk-protien-related IgA may trigger the symptoms, whether cow’s milk protien is present or not. Regardless, it is currently diagnosed as ‘infant cow milk protien allergy’ - until they have a better term for it, and the resulting damage to the brush border of the intestine is the same, and removing cow’s milk from the mom’s diet does reduce symptoms in about 35% of the suspected cases, and food challenges verify about 22% of suspected cases are reactive to maternal consumption of dairy in a verifiable way.)[/end hijack]

I did feeding management to suppress the oversupply (plus donated a bunch of milk, because pumping was like opening a fire hose - an ounce a minute, literally), and dropped dairy from my diet, and doing both worked. I’ve done dairy challenges after my supply normalized, and my ped agrees that Bren definitely has a ‘dairy allergy’ (though it appears to be fading like most do in the first two years!). Still, cow milk protien allergy is sufficiently rare that I’d lean toward checking other factors (like timed feeds when breastfeeding), before cutting out milk.

Anyway, long story short, in answer to the OP: As noted many times above, babies are born to consume lactose. They are born to do it, and if they can’t, they starve until they’re given something they can digest.

Someone asked about lactose-free formulas? Lactose-free formulas are in response to lactose overload issues, and diarrhea from other causes (where addition of lactose may make things worse because of existing damage to the intestine). There is some concern in the medical community about using lactose-free formulas, because there are no long-term studies of the impact of it, but short term studies show no clinical difference between outcomes for lactose-free vs. lactose formulas. Because it may reduce symptoms of diarrhea and gas, many doctors recommend it (despite guidelines not to) as helpful for treating infant colitis. Its use as a standard formula has been questioned by some medical professionals. There’s a feeling that instead of dealing with the cause, many parents turn to lactose-free formulas to treat the symptom (even if it isn’t a good idea). In 1999, Lancet published a comment on the unethical promotion of lactose-free formulas - I doubt it has improved any since.

I often wonder if people who are lactose intolerant as adults (but have Northern European heritage) are just allergic to something they’re eating, and are suffering the same consequences as the babies are… no lactase, no tolerance for lactose.

Here’s a nice article on the subject of ‘lactose intolerance’ in babies (and its link to colic - you’d probably be surprised how often I find that colicy babies are suffering a lactose overload on the breastfeeding support forum I support - either due to maternal low-fat diet, or oversupply, or timed feeds reducing the fat intake - and how FAST it resolves when they just approach the feeding process a little differently).:

More on the general topic (including diagnostics):

(oh, and BTW, ‘acquired’ tolerance from consuming more lactose comes from proliferation of lactose-consuming bacteria, not from increase in lactase production)

Interesting post, but I find I have a number of problems with it.

First, I’ve been researching the subject for 20 years and I have never come across the term “lactose overload” before. I also have not encountered the statement that a milk protein allergy will damage the brush border causing an intolerance. Celiac disease does this, but not milk protein allergy.

So the conference paper linked to was a surprise. I do have to note that the ALCA stands for the The Australian Lactation Consultants’ Association (ALCA Ltd). I can’t find anywhere on their website what the qualifications are for membership or how formal the 1997 Conference was.

Similarly, I looked at the footnotes for the more surprising statements.

The Lancet “study” is available on the Net for reading. The Lancet is certainly a legitimate medical journal, but it also publishes quick letters that are in the way of advice rather than formal peer-reviewed studies. And the condition described here is a fairly specialized one. It also has nothing to do with milk allergies.

Oddly, both of the footnotes on milk allergy causing brush border damage are to non-medical journal articles. They are not on the Net, so I can’t judge their worth or where they got their information from.

My understanding is that cow’s milk protein allergy is an entirely different issue from lactose intolerance. One does not cause the other, although it is possible to have both simultaneously. This appears to be extremely rare in infants, however.

Secondarly lactose intolerance certainly exists, and can be caused by any trauma to the intestines, including what is typical and incorrectly called the “stomach flu.” This is a temporary condition and the infant will be able to drink milk again when the intestines heal.

Soy milk formulas are common because a great many babies do indeed have cow’s milk protein allergies, although the majority grow out of them by about the age of three, because of secondary lactose intolerances, and because of other, fortunately rare, intestinal problems.

I assume that hedra claims that there are no long-term studies of soy formula because that paper says so.

No longer true. The most important one, I believe, is Exposure to Soy-Based Formula in Infancy and Endocrinological and Reproductive Outcomes in Young Adulthood, by Brian L. Strom, MD et al., which found no significant differences in adults who has participated in a soy feeding study as infants (although some menstrual problems were noted).

While it is trivially true than ingesting more lactose than your body has lactase to digest it will create symptoms - in fact, that is the definition of lactose intolerance - “lactose overload” in babies is not something I would say nursing mothers normally have to deal with. At least I would want far more medical evidence than that paper supplies before I took it seriously.