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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 food 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.


So...here 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.


Food Proteins Do Transfer into Breast Milk


We know a nursing parent's diet is important while breastfeeding. We also know what we 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, it’s easy for the medical field to push formula to solve the problem. This can be stressful for families that wish to breastfeed.


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




How Long Does Dairy Last In 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 was 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 two weeks to improve 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 showed that of 23 lactating participants, 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 people, peanut proteins were undetectable after 8 hours of consuming peanuts. [3]


Let me repeat that, undetectable after 8 hours.