The answer to whether breast milk protects a child against developing asthma is complex.
Two new research papers introduce additional pieces of the puzzle, but still more research needs to be done for more definite answer to the question.
These papers are not easy-to-read for non-scientists like me, but if you are a scientists, these might provide interesting insights!
So if you want a quick answer: it definitely is a complex subject where you have to dig quite deep into the research.
These new research papers seems to suggest breastfeeding can be protective against asthma in certain situations, in certain populations and subgroups.
For example, the conclusion of the first paper seems to suggest breastfeeding can reduce the risk of asthma in babies without eczema in the first year of life.
"Longer duration of breastfeeding was associated with a reduced odds of
asthma among children without eczema in the first year of life; this
association was masked before stratification by eczema in infancy.
Paper Number 1: The interplay between eczema and breastfeeding practices may hide breastfeeding's protective effect on childhood asthma
Paper number 2: Air pollution during infancy and lung function development into adolescence: The GINIplus/LISA birth cohorts study
Zhao Q, Kress S, Markevych I, Berdel D, von Berg A, Gappa M, Koletzko S, Bauer CP, Schulz H, Standl M, Heinrich J, Schikowski T. Air pollution during infancy and lung function development into adolescence: The GINIplus/LISA birth cohorts study. Environ Int. 2020 Oct 21;146:106195. doi: 10.1016/j.envint.2020.106195. Epub ahead of print. PMID: 33099064.