The presence of food protein in human milk is a complex and varied phenomenon that depends on various factors, including the type of food, the amount consumed, the timing of exposure, and the individual differences among individuals. Research has shown that not all ingested proteins enter human milk. For example, in a small study published in 2019, milk protein molecules were detectable in the blood of breastfeeding mothers after they had consumed dairy products, but the concentration peaks were not high enough to be detectable by most commercial tests for food allergies. Moreover, the study suggested that the presence of these peptides in breast milk does not necessarily mean they will cause an allergic reaction in the infant.
When certain food proteins, such as milk proteins, are detected in human breast milk, they tend to clear from the milk within 24 hours, at times, much quicker, within 6-8 hours. The timing of exposure and the size of the proteins also play a role in determining the persistence of these proteins in the milk. For example, in a study published in 2010, peanuts were detectible in breast milk shortly after they were ingested, and the peak concentration occurred within the first hour. However, this does not necessarily mean there was an allergic reaction to the peanut proteins in all women, nor does it necessarily imply that the milk was still contaminated with these allergens for weeks to come.
In addition, the form of the ingested food and whether it has been cooked can significantly impact the detection and concentration of food proteins in human milk. A study published in 2004 found that boiled eggs were less likely than raw eggs to be detected in human milk because eggs, unlike meats, are mostly protein but do not contain much fat. The study also found that cooking affected the protein concentration differently depending on the method.
Overall, the presence and duration of food protein in human milk is highly variable and cannot simply be generalized to a specific period for all individuals. It is typically recommended that for the management of food sensitivity or allergies in infants, mothers avoid known triggers from their diet and seek support from a healthcare professional if they have concerns about their milk potentially containing allergens.
In conclusion, while some proteins may remain in breast milk for days, others may be cleared quickly or may not pose a risk to the infant. It is important for parents to monitor their infant's symptoms and react accordingly to address any potential food allergies or intolerances while continuing to provide them with the benefits of breast milk, which offers essential nutrients, protection, and emotional connection.