Science Questions

Can proteins eaten by a mother get into her breast milk?

Sun, 2nd Aug 2009

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Conrad asked:

Can proteins ingested by a mother reach the baby in her breast milk?


A glass of milkChris -   Well, the answer is... I was intrigued by this (and my own observations at home) enough to want to look this up because my wife had been saying to me many times - because we now have two small children, both were breast fed - that when she ate certain things, it seemed to make the children more prone to getting a belly ache and have wind than when she ate other things.  I said: ďWell itís nonsense.  Itís coming in as breast milk.Ē  And, you know, how can that be affected by what the mum eats?

So Iíve been having a poke around and thereís a paper published in 1921; WR Shannon who found that proteins which are in the motherís diet that can pass unchanged into breast milk and thereís another study which was done: Killshaw and Cant.  They published in the International Archives of Allergy and Applied Immunology in 1984, and they did a very thorough study.  They took 29 women who are breastfeeding.  They took samples of their blood and their breast milk and then gave them an egg and half a pint of cowís milk to drink.

Then they took samples of both of those blood and breast milk samples again, at various intervals afterwards.  They measured the levels of these proteins and they used various measures to see whether the proteins where coming through into the breast milk.  And they found that after the mother ate those things, they could pick up the egg and the milk proteins intact in her blood stream between 1 and 2 hours later and it peaked in breast milk 4 and 6 hours later. 

So this is really interesting.  It shows things that are in the motherís diet can pass unchanged through into the baby and why they say thatís important is because this may be a way in which the babyís immune system gets educated against the things that it will be eating in the future.  Because we know that the babies when they are first born have this very plastic immune system that needs to be programmed what it has to recognize as a friend or what it needs to recognize as a foe.  So this, perhaps, is why breast feeding is so important in helping the immune system get educated like this because the things are presented in the right context at the right time.


Milk is made up mostly of water, globules of fat (yellow) and lumps of caesin protein called micelles. The micelles are covered with negative charge which repels other micelles. © Dave Ansell

Helen -   Can it also be a problem?  I think I have heard a story about in the Arctic, in fact, that some of the Inuit women there who eat a lot of whale meat, their breast milk becomes whatís classified as contaminated waste.  Some of the contaminants inside the whale meat;  things like the mercury that build up in those animals living in the sea comes out in her breast milk to the point that it can be measured and it might be even damaging to their offspring, which is just disastrous. The idea that the environment is so contaminated and itís getting through our own systems.  Isnít there also a story about if you have a dram of whisky that it calms down the mother and the baby.

Chris -   Now this is definitely true.

Helen -   I donít think we necessarily condone that but...

Chris -   But the way breast milk gets made is that there are specialised cells in the breast tissue which have a very high blood flow.  The blood goes pass the breast cells; the cells remove from the blood various chemicals and concentrate them in milk.  So theyíre using chemicals that come out of the blood, water from the blood and theyíre making milk.  Anything that dissolves well in fat can move well through the blood vessel wall through those cells and into the ducts that line the breast.  So therefore drugs and other things like alcohol can end up getting concentrated in breast milk so women have to be a bit careful when they take certain drugs because they can concentrate in the breast milk.  And what she says about people who eat a diet which may be contaminated, of course thereís a risk but, you know, we didnít evolve to combat heavy metal poisoning.  We evolved to give our children the best start in life.  So, I guess, the kind of that is unfortunate side-effect but the bottom line is breast actually best for the most part.

Helen -   Oh yeah, absolutely, yeah..


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Conrad Berube asked the Naked Scientists: Howdy Newton's Nude-ones! † I have a friend in the office here who is breast-feeding an infant. † She says that she can't eat dairy products because the milk proteins would pass from her digestive tract into her breast milk and cause an allergic reaction in her young son (who had been suffering from bloody stools prior to her altering her diet). † † This sounds a bit like Food Protein-Induced Enterocolitis Syndrome-- but my understanding is that FPIES is the result of infants being directly exposed to foods not to their residuals in breast milk. † Further, the idea that protein in a mothers diet could cross into breast milk contradicts my understanding of digestion and glandular secretion. † Although I can understand how other dietary components could find their way into breast milk and thus affect a babys digestion, aren't proteins too big to get into breast milk in the way my friend believes they do? † Conrad Berube What do you think? dracon, Tue, 4th Aug 2009

I think it depends...

Does the baby allergic to the amino acid compounds in it or the "crude" protein itself?

...I think... wanhafizi, Tue, 4th Aug 2009

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