Looking at the Question of Whether Probiotics “Go Through the BreastMilk”

Recently I’ve been seeing advice, sometimes from professionals of different sorts, that mothers of colicky babies should take probiotics internally (by mouth) so as to pass them on to the baby through the breast milk.  The idea based on some fairly good ideas that babies who acquire healthier gut flora earlier will have less gas and digestive upset and less crying.  It also assumes that probiotics can pass through the breastmilk to the baby when taken by mouth by the mother.  Sometimes a study is even cited that seems to provide evidence for the practice.  It also assumes that infant colic or excessive crying is usually or always caused by digestive upset that can or should be treated by any intervention.  That’s not an issue that I’ll address here, as it is worth a tome of examination on its own.  Certainly it is outside of the scope of practice for most non-medical practitioners who encounter infants to prescribe medicines to the infant for any condition, so suggesting that the mother can harmlessly pass on a safe supplement she ingests though her breast milk rather than directly dosing the baby would seem to be more acceptable.  Those who are giving this advice, however, don’t seem to have actually looked at the evidence they’re citing and are unfortunately mischaracterizing the results.  Basically, this practice can’t possibly work the way it is proposed, and the evidence cited does not support the conclusion in the slightest.  Here we’ll discuss why this simply doesn’t work the way people propose, not for anybody.

What is a probiotic?

Probiotics are your digestive flora.  Your food is digested, in part, by lots of microorganisms (such as bacteria) that live in your intestines.  They break down the food so your body can use it.  They also exist there to kill harmful microorganisms, ones that cause diseases, that may get into your digestive tract.  You don’t actually want to get these bacteria into the rest of your body, like into your blood.  You could get an infection from that, so your body keeps them separated neatly from the rest of your body by the lining of your digestive system, a membrane that allows some very small things like vitamins, sugar, and protein molecules through, but not large things like whole cell organisms.  Sometimes a person’s digestive flora can get messed up by an infection, a deficient diet, or by taking antibiotics.  Antibiotics kill bacteria, and do kill them indiscriminately, even the ones you want.  Probiotics are a dietary supplement of the sorts of good digestive bacteria you want in your gut.  They can also be found in certain types of fermented foods and yogurt.

Why would anyone want to have a baby a probiotic?

Babies are born with sterile guts.  When they’re born, babies don’t have any digestive bacteria in their intestines.  They haven’t been colonized yet with anything, good or bad.  This is part of the reason why babies’ digestive systems are said to be “immature.”  They don’t have the bacteria in the first few weeks of life to break food down like old people do.  It may also be a big reason for young infants to get gas.  The food they eat rather ferments in their guts instead of being digested because of immature gut flora.  The infant’s gut is usually colonized by breastfeeding.  Indeed, if you test a breastfeeding mother’s nipples for bacteria, you’ll find all sorts of them growing there.  Frightening amounts, if you have no idea of the context!  There have even been reports on the news of how much digestive bacteria is found in milk bank human milk.  Well, of course there is.  A lactating woman’s nipples are colonized with all kinds of digestive flora that she’s colonizing her baby’s gut with during breastfeeding.  That’s how it normally happens.  There are recent studies that are showing that babies who are not breastfed end up with entirely different gut flora as a result of not having this source of colonization.

A few years ago, some practitioners where recommending giving babies probotic (like when I had my son), but I don’t think that any specific type was ever tested for safety or effectiveness in infants.  It doesn’t shock me that this didn’t last long under these circumstances and that someone looked for a way to deliver the probiotic to the baby without giving it to the baby.  Then a study that, at least when turned into a headline, came up that appeared to say that probiotics can benefit babies when taken by their mothers, it looks like it was grabbed onto for this purpose and all sorts of extrapolations from the data were made.  One of the extrapolations went as far as to say that the probiotics go through the breastmilk, so therefore if you want to colonize a baby’s gut earlier, mom should take them.  This extrapolation went too far.  Things just can’t work that way, and the evidence for this extrapolation isn’t there.

 So what is the “evidence” and recommendation?

In the last few months I’ve been seeing recommendations on mom’s groups that moms start taking probiotics as a cure-all if their babies have gas or reflux.  Not give it to the baby, but take it themselves.  Usually the most expensive, refrigerated live stuff is recommended.  It also plays into our cultural anxieties about baby care, throws another unneeded expense at overburdened parents, and ultimately lands in the category of “colic woo.”  However, getting back to rationality, it has been repeated and blogged about often enough that it’s becoming accepted wisdom in some circles.  I’ve even seen some infant care professionals throwing it out there, but citing secondary sources.  The recommendation is that the mother should get on a regimen of live probiotic cultures on grounds that there is a study that proves that probiotics “go through the breastmilk.”  This is to say, you can eat probiotic microorganisms, and they will get into your milk supply and be swallowed by your baby and colonize the baby’s gut, thereby improving the symptoms of gas and “reflux.”

Most of the sources I saw for this were anecdotal in nature or secondary, meaning first person narrative blog entries.  However, the idea fascinated me because all the claims kept saying that there was evidence.  I like to keep an evidence based practice, and so I went on a hunt for this evidence.  Eventually I found this article as the primary source for the claim:

Probiotics during pregnancy and breast-feeding might confer immunomodulatory protection against atopic disease in the infant.

If one reads this article, or just the abstract that is available to the public, you may notice that no mention of use of probiotic by the mother benefiting the baby’s digestive health is made at all.  Atopic disease is a type of allergic disease, and in this case, specifically atopic eczema.  Indeed, what the article does describe is that if a mother who is genetically predisposed to having babies with confirmed IgE mediated allergic disease, taking probiotics during pregnancy and lactation seems to give a high level of protection of the baby developing allergic eczema in the first 2 years of life.  The mechanism of action appears to be that the mother’s immune system benefits by taking the probiotic, and consequently her breasts produce higher levels than average an anti-inflammatory factor (TGF-beta2) that her baby then receives in the milk.  They believe that the extra anti-inflammatory factor ingested by the baby is protective against allergic skin inflammation.  Please note that this is a study about allergic skin inflammation.  The thing passed in the milk is an anti-inflammatory factor, and not the probiotic.  And this is the only good clinical evidence I could find that has been cited to support the claim that probiotics should be used for colic and reflux on grounds that they “go though the breast milk” and can thereby benefit the baby.

So can we extrapolate from the data?

In short, no.  Not this to this conclusion.

Probiotics are whole cell microorganisms.  In order to make it from your mouth to your baby’s intestine where they’re to do good they must pass the following steps:

1.  Be swallowed by you.

2.  Survive the acidic environment of your stomach and pass to your intestine.

3.  Pass though the membrane lining of your intestine into your bloodstream.

4.  Survive in your bloodstream for some time.

5.  Be selected out of your bloodstream by your milk ducts and pass through a cell membrane into your milk duct.

6.  Be drunk by your baby.

Certainly you can consume the probiotics, and some survive the trip through your stomach.  But that’s where the physical possibility of this journey ends.  As I mentioned before, the lining of the intestine of human beings is designed to allow certain types of molecules to diffuse through.  It is specifically designed to not allow whole cell microorganisms through.  It doesn’t even allow large sugars though. (Which is why the onions and broccoli you eat makes you fart, but cannot make your baby fart.  The sugar responsible is too big to pass through your gut wall.)  If it did, you’d die a horrible death from bacteria flooding from your intestines because your intestines are full of bacteria that need to stay safely there.  Before someone says, but it really, really, worked differently for me because it did and I say so, it did not.  No anecdote can disprove a fact of all human anatomy here.  Yes, folks are different.  Different enough that some people fart from broccoli and some do not.  Different enough that some people taste a horribly bitter flavor in broccoli and some do not.  Those variations are within the explainable bounds of human biology.  No one is a special enough snowflake that the whole cell organisms of probiotics and no harmful bacteria pass through your gut wall into your blood.  No probiotics got through anyone’s intestinal lining after they swallowed them, not unless they are critically ill.  Even in the totally unproven theory of leaky gut diseases, nothing as big as whole cell bacteria are proposed to get through.  You’d have sepsis if they did.

But let’s pretend it did for the sake of absurdity and what would happen in a pretend world because I want to prove that the probiotic still can not get to your boobs.  The probiotic microorganism, having left your intestine, would then be in your bloodstream.  Remember, even if it’s a good bacteria, a probiotic is a digestive (think fecal) bacteria.  At that time, it would be detected as a foreign body by your immune system and killed like any germ.  But let’s even say that didn’t happen and your immune system saw it and waved, “oh, hello good bacteria!  I can see you mean well; carry on,”  and didn’t destroy it, what would happen then?  In order it get into your breastmilk, these whole cell microbes would have to cross the cell membranes into your milk ducts.  Normally only smallish molecules like proteins and smaller sugars do this, along with some drugs.  Not even all drugs are good at it because they are too big; insulin, for example, is too large to pass from the mother’s blood stream through the breast milk to the baby.  Whole cell microbes are orders of magnitude larger than molecules.  They will not pass through this membrane into the milk.  Therefore, there is no physical way that probiotics taken orally by the mother can be passed one through the breast milk to the baby.  There are too many normally functioning biological barriers.  This recommendation is based on flawed logic and a flawed understanding of basic biology.  No one’s body is that leaky and bad at keeping out foreign microbe  unless they are suffering from an imminently life threatening illness.

Are there any benefits and what is learned?

Yes, it does seem there are.  In mothers who have a strong family history of allergic disease, diagnosed IgE mediated reactions to allergens, taking probiotics in pregnancy and during lactation may help prevent the skin manifestations of allergic disease in the child.  Perhaps it we might think it would help lessen other manifestations of allergic disease.   It also tells us that the benefit comes from improving the mother’s immune system by increasing her levels of naturally occurring anti inflammatory factors, and not by action on the baby’s gut.

However, this study tells us nothing about a lot of things that seem to be drawn from it here.  It says nothing about people who do not have a strong family history of IgE mediated allergic disease.  It does not tell us anything about digestive health of the infant.  It does not tell us about non-allergic digestive problems of the infant.  It does not tell us anything about non-digestive excessive crying.  It especially cannot tell us anything about the digestive flora of the infant; that was not studied or remarked on in any way.  And it does not prove that whole cell microbes can pass from the mother’s digestive tract to the breast milk.



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