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What Is the Truth About How Long

Proteins Last in Your Breastmilk?

You’re told your baby may have a protein intolerance or allergy. You need to change your diet to continue breastfeeding. You feel like you’ll do whatever you have to do for the health of your baby.


Then you’re told it may take up to two weeks for the proteins to clear out of your system. And then two more weeks to clear out of your baby’s system.


Something is wrong with your baby and you’re concerned. And now you have to wait a month for hopes of improvement. Even worse, some groups state that it can take up to 8 weeks!?


The timing doesn’t seem to add up and the medical professionals don’t seem confident in their answers either. you are reading every label and hoping that your breast milk isn’t harming your baby.


Here at Free to Feed our mission is to provide scientific evidence and help mothers continue breastfeeding their babies with food allergies or intolerances.


Here are some facts backed by science on how long certain food proteins remain in breastmilk.

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Food Proteins Transfer into Breast Milk


We know a nursing mother’s diet is important while breastfeeding. We also know what she consumes goes to the baby. When you’re told you need to change your diet, you have lots of questions.

How much is getting to the baby?

How long do proteins stay in my breastmilk?

How long are the proteins in my baby’s system?

It’s impossible to answer these questions definitively. There is

still a great need for more research on protein transfer and

breast milk studies. We know the medical field is lacking in this

research as the number of infant food allergies and intolerances

continues to grow.

We’re happy to say Dr. Trill is currently holding the first study looking at cow’s milk protein and soy!


It’s hard to place a value on breastmilk. Some refer to it as liquid gold. Even the best formula cannot replicate what breast milk gives to infants. Fed is best and this is true.


But if your baby has allergies or intolerances, it’s easy for the medical field to push formula to solve the problem. This can be stressful for mom and baby if the wish and plan is to breastfeed.


Let’s take a look at some common food allergies including cow’s milk protein, peanuts, egg, and wheat.


How Long Is Dairy in My Breast Milk?


Cow’s milk protein allergy (CMPA) is the most common allergy or intolerance for infants. If your baby is suspected to have a food allergy, it’s likely recommended to stop all cow’s milk protein (all forms of dairy products) first. This is where you’ll likely get answers about it taking weeks to leave your system.


A small study showed lactating mothers who ingested milk prior to being dairy free, found cow’s milk protein peaked at

2 hours post-ingestion and were undetectable at 6 hours [1]. Although the study was small it was using mass spectrometer ion intensity testing which is incredibly accurate.


Let that sink in for a moment... Undetectable at 6 hours!


Also, the Journal of Pediatric Gastroenterology and Nutrition reports “for an immediate reaction the maternal elimination diet needs to be maintained for only 3 to 6 days. If delayed reactions are suspected (eg, allergic proctocolitis), then the diet should be continued for up to 14 days. If there is no improvement, then it is likely that diagnoses other than CMPA are the cause of the symptoms and the child should be further evaluated.” [2]

If we take a step back and think about this we can learn and understand from these studies. If cow’s milk protein was still present in breastmilk weeks after consumption, then acute reactions would continue past a few days. Chronic reactions would take longer than four weeks to resolve as well.


Are you scratching your head yet?


How Long Are Peanuts Detected in Breastmilk?


Most of us are aware that peanuts have been a growing allergic concern for children and adults. Remember when they used to hand out peanuts on airplanes? You won’t see that ever again due to the increase in peanut allergies among the population.


But how long are they in breastmilk?


A study conducted in Toronto that showed that of 23 lactating women, only 11 showed peanuts in their breast milk after consumption. Peak levels were noted at 1-2 hours after ingesting 50 grams of peanuts [3].


In 10 of the 11 women, peanut proteins were undetectable after 8 hours of consuming peanuts [3].


Let me repeat that, undetectable after 8 hours.


Although this is only one study, it’s fascinating that in some women peanut protein was never detected in their breast milk. There is likely a multitude of factors contributing to this. However, we can learn that not all proteins get into breast milk every time.


How Long Does Egg Last in Breastmilk?


Scientists have found that daily consumption of egg did not result in the accumulation of egg protein in breast milk over time in a study where lactating women were giving a daily muffin containing egg [4].


We think or we’re told the more we consume something the more it “builds up” in our system, thus the longer it takes to clear out. The egg study shows us this isn’t the case.


The same study also found that egg concentration peaked within 8 hours of consumption and that concentration of egg protein was higher after cooked egg consumption as opposed to raw egg [4].


This provides more information on how food being cooked can alter the protein concentration. So there is a clear difference between eating a muffin and a plain egg.

How Long is Wheat in Breastmilk?


There is a specific protein in wheat called gliadin. A study was conducted showing that 53 lactating women consumed 20 grams of wheat and only 41 tested positive for gliadin [5]. This again shows us not all proteins get into breast milk with consumption.


Another study showed 6 women who were put on a 3 day wheat-free diet and their breastmilk did not detect gliadine [6]. This could mean wheat cleared of their system much sooner than 3 days, but it definitely didn’t take two weeks!


The Science On How Long Food Proteins Are In Your Breastmilk


There are important key points that we want you to take with you from reading this.

First, not all ingested proteins enter into breastmilk (the peanut and wheat example). Second, when proteins were detected they typically cleared breastmilk within 6-8 hours (cow’s milk, peanuts, and egg).


This goes against what most medical professionals say. Unfortunately, leading to more worry and confusion from mothers.


It gives us hope at Free to Feed and we understand the importance of continuing to breastfeed through infant allergies and intolerances. If you want to continue breastfeeding, we’re here to help you.


For all the scientific data we have found and to learn more, you can visit our page on True/False Allergens For Weeks here.


To have a one-on-one consultation about your journey, sign up here!



  1. Picariello, Gianluca, et al. "Excretion of dietary cow’s milk derived peptides into breast milk." Frontiers in Nutrition 6 (2019): 25.

  2. Koletzko, S., et al. "Diagnostic approach and management of cow's-milk protein allergy in infants and children: ESPGHAN GI Committee practical guidelines." Journal of pediatric gastroenterology and nutrition 55.2 (2012): 221-229.

  3. Vadas, Peter, et al. "Detection of peanut allergens in breast milk of lactating women." Jama 285.13 (2001): 1746-1748.

  4. Palmer, D. J., M. S. Gold, and M. Makrides. "Effect of maternal egg consumption on breast milk ovalbumin concentration." Clinical & Experimental Allergy 38.7 (2008): 1186-1191.

  5. Troncone, R., et al. "Passage of Gliadin Into Human Breast Milk." Pediatric Research 20.7 (1986): 696.

  6. Chirdo, F. G., et al. "Presence of high levels of non-degraded gliadin in breast milk from healthy mothers." Scandinavian journal of gastroenterology 33.11 (1998): 1186-1192.

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