Hi everyone, welcome to the LactFact weekly podcast, which highlights recent, clinically relevant research, policy statements, and protocols that you, as a practicing lactation professional, should know about. I am your host, Dr Anne Eglash. I am a board-certified family physician and breastfeeding and lactation medicine specialist at the University of Wisconsin School of Medicine and Public Health.

This podcast is written and produced by the nonprofit organization IABLE, which is the Institute for the Advancement of Breastfeeding and Lactation Education. There are no commercial funders for this podcast series.

Today’s LactFact is about food proteins in breastmilk. More specifically, I want to focus on the factors that determine transmission of food proteins into breastmilk, and how long food proteins stay in breast milk after ingestion.

Many exclusively breastfed infants are suspected of having sensitivity to dairy or other food proteins in their mom’s breast milk because of various symptoms such as persistent vomiting, infrequent pooping, allergic proctocolitis with blood-streaked stools, generalized fussiness, and significant reflux symptoms.

I've heard from several physicians in my community and from around the world that when exclusively breastfed infants are suspected of having food sensitivity, their mothers are instructed to stop breastfeeding for two weeks to get all the protein out of their breast milk, which means that they end up recommending a hypoallergenic formula for 2 weeks.

First of all, this claim that it takes two weeks for food proteins to leave breast milk is not evidence based. I want to talk about this more and I am citing the article:

‘Breastfeeding: maternally Transferred Allergens in Breastmilk: Protective or Sensitizing?’
The authors are Frauke Schocker and Uta Jappe
Published – Molecular Nutrition Food Research in 2021

The authors describe the different factors that determine the transfer of food proteins into breast milk. After maternal ingestion of a food protein such as dairy, the maternal gut’s digestion of the food protein will determine the protein variation that ends up in breastmilk. In other words, the food protein might be digested in such a way that the protein is less likely to cause the infant to have an allergic response. After protein digestion, the protein particles cross the maternal gut lining to a variable extent, such that it’s possible that not all of the food proteins end up in the maternal circulation.

The food proteins that do end up in maternal circulation are challenged with crossing the mammary gland epithelium into breast milk. Again, we have this variability among lactating individuals, such that the permeability of the mammary gland epithelium will vary at different times of day, different stages of lactation, and whether there are other factors that influence permeability such as mastitis or overproduction.

The studies that have been done on the timing of food allergens in breast milk after maternal ingestion have included cow’s milk, wheat, egg, and peanut.

When we look at studies on transfer of proteins into breast milk, it is clear that there’s a wide variation between people and even within individuals, making it impossible to know precisely how much food protein and in what form will be present in breast milk. Because the food proteins differ in terms of what form they end up in breastmilk, it's hard to predict what the infant’s immune response would be.

Several studies show that many women don't transfer food proteins into breastmilk. For example, a few studies among women who were given food challenges demonstrated that 15% of women did not secrete the cow’s milk protein, beta lactoglobulin, into their breast milk and 25% of women did not have any detectable ovalbumin, from egg consumption, in their breastmilk.

The majority of the studies that have looked at how long it takes ingested food protein to get into breastmilk found that the average peak concentration of proteins occurs at around 1-4 hours after ingestion.

The excretion of food proteins, or basically the duration of time the food protein stays in breast milk, varies, but in general studies done with peanut and cow’s milk proteins show that the proteins are excreted within hours, often 6-12 hours, and certainly within 24 hours.

Unfortunately, because of lack of education in the field of breastfeeding medicine, physicians often don't understand the ramifications of asking the mother to stop breastfeeding for two weeks.

There are risks of bottle preference, changes to the infant gut microbiome from formula, in addition to the risk of infant illness by taking away breastmilk.

The mother has the risk of complications from pumping such as pump trauma, mastitis, and changes in milk production, which no longer matches the rate of infant milk intake.

These breastfeeding complications increase the risk of premature weaning, which increases long term health risks for both the infant and parent.

Another consideration here is that these infant reactions to food proteins are very rarely dangerous. Therefore, if the mother stops eating the suspected food, the baby will be fine to be exposed to the food protein for another 6-12 hours, at which point the food proteins will be out of the breastmilk anyway.

So let’s get the message out there that there is no reason to interrupt breastfeeding when there is a suspicion of infant sensitivity to food proteins, unless the infant has had a life-threatening reaction.

The main intervention should be providing education for the mother or lactating parent on how to avoid the food protein and options for dietary substitutions.

Thanks for listening. I encourage you to check out IABLE at lacted.org to learn more about our educational projects, courses, educational handouts, videos, events. By becoming a member, you are not only supporting our projects, but also receiving a discount on educational courses, participation in our google group listserv, and a free pin on our LactMap.

I will talk to you again in 2 weeks!