This newly published study† has been creating waves in the EPing community. Here’s my take. I’m sorry that I can’t really do a TL;DR for this, but I really want to stress that starving a child through nursing is definitely worse than feeding them well with pumped milk.
Firstly, this is a cohort study, which means the researchers are following the children throughout their childhood to find relationships between breastfeeding and various outcomes. This newly published article is just one of many findings that will come from the study. I am fairly familiar with the study and the researchers and rest assured that it is a rigorous study with reliable findings (especially given that it was published in Cell, which is an extremely hard journal to get published in). I also know that the researchers are vehemently in favor of ALL kinds of breastfeeding and would DEFINITELY agree that pumping is worth all the time and effort!
Secondly, there is likely always going to be more “bad” bacteria in pumped milk because of the equipment it passes through. A PhD researcher at Cornell I know did her thesis on this and found that simply sterilizing pump parts (even in microwave bags) or dishwashing reduced the bacterial contamination greatly. BUT even she questions “so what?” – there were no reports of sickness in the babies from the pumped milk that had more contamination. The levels of contamination from well-cleaned pump parts is probably irrelevant (poorly cleaned pump parts or immunocompromised babies is another topic though).
Thirdly, yes, this study finding does provide evidence in favor of nipple-saliva transfer. One study a while ago‡ found that a baby’s saliva does backwash into the milk ducts when they DN. It has be theorized that this would change the composition of the milk, but there hasn’t really been any evidence about how, since we also know that mom being in the same environment as baby’s germs also changes milk composition. This study really indicates that the microbiome (that all the different living organisms, good and bad) of the milk is on the whole different between those who only pump and those who directly nurse.
Fourthly, there is SO much research out there about the milk microbiome and the effect it has on the baby’s own microbiome. What those other studies have found is a HUGE difference in the milk microbiome between different people, different living environments, different countries…the list goes on and on. This is all REALLY new science so the consequences of it are really just not known right now.
Fifthly, we really should think for a second about the microbiome of pumped milk versus formula. Formula has little to no microbiome (you could argue that probiotics in formula add something of a microbiome, but if you use water hot enough to kill any pathogens in milk powder, as recommended, you’d kill those probiotics anyway). And there are also studies about the negative effects of formula the gut microbiome of babies. But again, rest assured, formula mamas: we still don’t really know what lifelong consequences this actually has.
Lastly, this study is just a piece of information. Could it lead us to greater insights in the future? Yes. If findings like this enabled us to add something to pumped milk (like the beneficial bacteria that might be missing from it) to make it even better, would that be a good thing? IMO, yes. Are parents still doing amazing jobs, making sure their babies are fed? DEFINITELY YES!!!!!! Are they better parents because they’re feeding their babies in the best way that they can? DEFINITELY YES!!!!!!
† Moossavi, S., Sepehri, S., Robertson, B., Bode, L., Goruk, S., Field, C. J., … & Turvey, S. E. (2019). Composition and Variation of the Human Milk Microbiota Are Influenced by Maternal and Early-Life Factors. Cell host & microbe, 25(2), 324-335.
‡ Ramsay, D. T., Kent, J. C., Owens, R. A., & Hartmann, P. (2004). Ultrasound imaging of milk ejection in the breast of lactating women. Pediatrics, 113(2).