Tuesday, February 01, 2011

Why I am against the raw milk movement

Disclaimer: I do not claim to be an expert on this topic. I do not work for any dairy operation or any company associated with the dairy industry. The discussion below simply expresses my opinions about this issue and is based on what I know from my Ph.D. in microbiology. If you disagree with these opinions, please let me know! Like I said, I am not an expert on raw milk, and I am open to other opinions and interpretations.

Being a smart consumer is about understanding both sides of an issue and making informed decisions. I try to adhere to this credo as much as possible because I think people are so inundated with information these days they do not always take the time to evaluate the information they are given. Who can blame them? Evaluating all this data takes a lot of work, but I do think it would behoove us all to ask, “Is that true? Does it make sense?” when a company/industry/etc. makes a claim that their product is better for us. Drinking raw milk instead of pasteurized milk is a new trend in my neck of the woods. My initial gut reaction as a microbiologist is that this is a bad idea. Pasteurization, along with other sanitary procedures, was put into practice to protect people from pathogens that can infect milk. If this practice is no longer used, aren’t we simply opening ourselves up to an increased chance of drinking infected milk?

According to the CDC and the FDA, the answer is yes. The CDC reported that, “Among dairy product-associated outbreaks reported to CDC between 1973 and 2008 in which the investigators reported whether the product was pasteurized or raw, 82% were due to raw milk or cheese.” (See http://www.cdc.gov/Features/RawMilk/ for the full article and http://www.realrawmilkfacts.com/scientific-references/ for the scientific references the FDA used in support of their stance on raw milk). While my search was not exhaustive, I did not find any scientific studies from peer-reviewed journals to refute these findings by the CDC. What do I mean by peer-reviewed? I agree with Wikipedia’s definition, which is “Peer review is a generic term for a process of self-regulation by a profession or a process of evaluation involving qualified individuals within the relevant field.” Obviously this method is not without fault, but I think it is the best method we have in the pursuit of truth. Therefore, I maintain my stance that there are inherent risks in drinking raw milk. However, the raw milk movement says that drinking raw milk has many advantages over pasteurized milk. Perhaps these advantages outweigh the risks of drinking raw milk.

What are the advantages claimed by proponents of raw milk? Since I couldn’t find a scientific article describing the advantages, to answer this, I will use information I found here http://www.raw-milk-facts.com/raw_milk_health_benefits.html because unlike many of the websites I found about raw milk, this site actually listed some references to support their claims. I would like to point out that some of their references are links to other like-minded websites, which I consider simply opinions not facts. Keep in mind, there may be better sites out there.

One of the proposed advantages to drinking raw milk is that pasteurization destroys active enzymes and antibodies in milk that have beneficial properties. Enzymes and antibodies are simply proteins, and yes, heat can denature, or inactivate, them. However, acids can also denature proteins, and the acidic environment of the stomach has evolved to do just that. In my opinion, I am not convinced that these enzymes and antibodies could have any appreciable activity once they have passed through the stomach. Also, antibodies and many of the beneficial enzymes they describe in raw milk such as lactoferrin, catalase, and lysozyme are already made by our bodies, so why would we need to get them from milk? Do we even know how active and in what quantities these enzymes and antibodies are in our bodies after ingesting milk? To me, until we answer these questions the claim that raw milk is more beneficial than pasteurized milk because there are more active enzymes and antibodies in raw milk is speculation at best.

Another proposed advantage of drinking raw milk is that people who are lactose intolerant should not have as strong of a reaction to raw milk. The reason stated for this is that raw milk contains Lactobacillus, a group of bacteria that can break down lactose into lactic acid. It is true that pasteurization can kill these bacteria. However, complete consumption of lactose in milk into lactic acid by these bacteria takes time, and as the bacteria consume lactose they produce more and more lactic acid which eventually leads to sour milk. Can these bacteria break down enough lactose before the milk goes sour to allow lactose intolerant people to drink it without having a reaction? I think the answer is that we don’t know, and because the magnitude of lactose intolerance can vary from person to person there are some people who cannot tolerate raw milk. To me, this proposed advantage is not compelling enough for me to advise lactose intolerant people to start drinking raw milk.

The presence of the enzymes listed above and production of lactic acid by Lactobacillus can inhibit the growth of other bacteria, including some pathogens. This is why some proponents of raw milk claim that it is safer than pasteurized milk. If that is true, then I would expect that we would only find pathogens infecting milk after pasteurization, but we know that pathogens can infect raw milk and pasteurized milk that is not kept in a sterile environment. Plus, the natural defenses found in milk are also found in your body. Pathogens have evolved mechanisms to overcome these natural defenses, which allow them to cause disease in your body. I do not find this a convincing argument for raw milk being safer than pasteurized milk.

There are other proposed advantages to raw milk that I have not mentioned, such as the probiotic effect conferred by ingesting Lactobacillus, which can easily be consumed in other, safer food products like yoghurt. In my opinion, most of the proposed advantages to raw milk are merely conjecture and do not outweigh the increased risk of contamination in raw milk. For me, that is the bottom line. You are free to agree or disagree!