Sometimes, I have my mind made up on a topic before I actually do research on it. And then, when I do some simple searching, the evidence points me in a different direction. At that point, I have a choice to either disregard the evidence and remain blinded in my presuppositions or take my blinders off and allow for the whole bright world to come into focus.
Raw Milk
For example, in the past few years, I’ve heard about the benefits of raw milk and how it is claimed to be nutritionally superior to pasteurized milk (i.e., heated to at least 145 ℉). Reading this on alternative health blogs and especially through the Weston A. Price Foundation (which I hold in high regard), I took this to be the truth. If our hunter-gatherer-farmer ancestors drank milk from the udder, why shouldn’t we? Why, in our modern day, should we “kill” all of the beneficial nutrients just in the name of safety when the risk of getting sick is already small? That reasoning felt enough for me, and I even went to a local store that sold raw milk, signed my life away with a waiver (basically, if you get sick or die from the milk, you can’t hold them liable), and sipped the milk for the next week (to be honest, it kind of freaked me out, but that was mostly in my mind. I did not get sick from it).
Somewhere along this journey, I decided to do some actual research (i.e., not blogs) on the benefits of raw milk (so, don’t take my word for these things– do your own research!). I set out with full intentions of finding evidence that pasteurized milk was inferior to raw milk in every way. But, what I found was surprising to me. Not only was I shocked to find out that if milk has any probiotics, it does not come from the milk itself but from the bacteria on the udder and environment; I found that many of the studies claiming the benefits of raw milk had biased conclusions. For example, this study entitled Recipe for a Healthy Gut: Intake of Unpasteurised Milk Is Associated with Increased Lactobacillus Abundance in the Human Gut Microbiome explains that 24 subjects stayed on a farm and consumed farm-fresh produce and raw dairy (1). After 12 weeks, their fecal bacteria showed an increase in lactobacillus, which is a beneficial probiotic species. The authors concluded that this was due to an increased intake of raw dairy products. This is a hasty conclusion, as the results of the study also showed the participants ate a statistically significant increased amount of vitamin A, vitamin B12, organ meats, and fish when compared to their baseline intake, which can all impact the microbiome environment (2, 3, 4, 5) (I encourage you to check out those linked references– every one of these nutrients/foods affects the gut microbiome!). Additionally, the majority of participants consumed low-fat dairy before the study began, but during and after the study, most had switched to full-fat dairy. All of these confounding factors likely had an impact on gut bacteria, and we can’t say that their gut bacteria changed solely because of the unpasteurized nature of the dairy they consumed.
What is perhaps more likely is that because these participants were living on and eating from an organic farm, the exposure to soil and microorganisms on a thriving farm impacted their gut bacteria. Did you know that lactobacillus does not come from milk (despite the name “lacto,” denoting milk)? In fact, when milk is extracted from a sterilized udder, no lactobacillus can be identified6. So, where does the lactobacillus come from? It comes from the surrounding environment, such as soil, fecal bacteria, and plant material. Because these study participants were consuming fresh produce from the farm (and likely interacting with the environment, such as harvesting the produce), their consumption of and interaction with lactobacillus from the environment would have increased (for example, from unwashed or gently washed produce) (6).
Similarly, fresh produce contains prebiotic fiber, which is “food” for beneficial bacteria in the gut, including lactobacillus species. We do not know whether or not simply eating this produce without any dairy would have increased lactobacillus levels in their stool. This study1 did not have a control group– which could have been a group eating the same foods with pasteurized milk instead of raw milk or a group eating the same produce with no dairy at all. Control groups are paramount in studies so that we may start to make sound conclusions, and because the above study did not have a control group, we couldn’t form more than a very generalized conclusion. An appropriate conclusion could be, “Living on and eating from an organic farm for 12 weeks may change fecal lactobacillus concentrations in healthy subjects.”
During my research of the raw vs. pasteurized debate, I came across a (document) addressing point-by-point the claims of the health benefits of raw milk, and why they are largely unfounded (with research to back it up) (7). Additionally, it detailed why some of these claims can actually be harmful to health. I highly recommend starting with this document, and then, if you’d like, you can try to refute the claims through further research. It was the straw that broke the camel’s back for me!
Who knew heating up milk could be such a contentious and well-studied topic?
References
- Butler, M. I., Bastiaanssen, T. F. S., Long-Smith, C., Berding, K., Morkl, S., Cusack, A. M., Strain, C., Busca, K., Porteous-Allen, P., Claesson, M. J., Stanton, C., Cryan, J. F., Allen, D., & Dinan, T. G. (2020). Recipe for a Healthy Gut: Intake of Unpasteurised Milk Is Associated with Increased Lactobacillus Abundance in the Human Gut Microbiome. Nutrients, 12(5), 1468. https://doi.org/10.3390/nu12051468
- Iyer, N., & Vaishnava, S. (2019). Vitamin A at the interface of host-commensal-pathogen interactions. PLoS pathogens, 15(6), e1007750. https://doi.org/10.1371/journal.ppat.1007750
- Guetterman, H. M., Huey, S. L., Knight, R., Fox, A. M., Mehta, S., & Finkelstein, J. L. (2022). Vitamin B-12 and the Gastrointestinal Microbiome: A Systematic Review. Advances in nutrition (Bethesda, Md.), 13(2), 530–558. https://doi.org/10.1093/advances/nmab123
- Zhu, Y., Lin, X., Li, H., Li, Y., Shi, X., Zhao, F., Xu, X., Li, C., & Zhou, G. (2016). Intake of Meat Proteins Substantially Increased the Relative Abundance of Genus Lactobacillus in Rat Feces. PloS one, 11(4), e0152678. https://doi.org/10.1371/journal.pone.0152678
- Zhu, Y., Lin, X., Zhao, F., Shi, X., Li, H., Li, Y., Zhu, W., Xu, X., Li, C., & Zhou, G. (2015). Meat, dairy and plant proteins alter bacterial composition of rat gut bacteria. Scientific reports, 5, 15220. https://doi.org/10.1038/srep15220
- Lactobacillus. Lactobacillus - an overview | ScienceDirect Topics. (2018). https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/lactobacillus
- Center for Food Safety and Applied Nutrition. (2011). Raw milk misconceptions and the danger of raw milk consumption. U.S. Food and Drug Administration. https://www.fda.gov/food/buy-store-serve-safe-food/raw-milk-misconceptions-and-danger-raw-milk-consumption