Guest Columns

Perspective:
Dairy Research

Raw milk is having a moment

John Lucey

John Lucey, director of the Wisconsin Center for Dairy Research at the University of Wisconsin-Madison, contributes this column for Cheese Market News®.

I have written before about the risks of raw milk consumption but, due to rumors of a change in federal regulations by the current administration that would greatly expand the sale of raw milk, I want to dig even deeper into some of the false claims being used to promote the consumption of raw milk.

My previous column on raw milk outlined the risk of consuming raw milk due to possible pathogen contamination as well as debunking claims about pasteurization destroying the nutritional properties of milk. Listeria contamination of dairy products remains a serious concern, and some recent surveys have detected Listeria monocytogenes in 50% of raw commingled milk silos. Listeria can grow at refrigerated temperatures but rapidly grows as the temperature is increased due to improper storage (or transportation conditions).

Some raw milk producers try to do some microbial testing on some of their milks, but this does not ensure the milk’s safety, although it might help with improving quality. Realistic testing at the farm requires trained individuals and calibrated and certified equipment. It should be done on every lot of milk produced, use only validated procedures, have high levels of sensitivity for all the key pathogens (be able to detect low levels) and detect key viruses like H5N1. I have many questions about any testing approach including: Would the producer issue a recall for any presumptive positives? Would they retain all tested samples and confirm any questionable or presumptive results at a certified lab? Are all the raw milk samples retained (not sold) until test results are known? Do they have a robust environmental monitoring program, and what actions do they take with positives?

I want to address several additional claims that I have heard about raw milk by some individuals. Some raw milk advocates claim that important health benefits of milk are lost by pasteurization, which is not correct.

These raw milk advocates often want to imply that human (breast) milk is the same as bovine (cow’s) milk, which is also not accurate. Pediatricians strongly recommend exclusive feeding of breast milk for infants during at least their first six months, mainly to get enough of the key components of human milk that may provide health benefits. They know that breast milk is not the same as cow’s milk.

Since human babies are very susceptible to infections, human milk has been designed to contain high levels of several protective compounds. For example, the colostrum (first milk produced after birth) in human milk may have up to 7g/L of lactoferrin and a similar concentration of immunoglobulins. In contrast, typical cow’s milk might have around 0.03g/L of lactoferrin and less than 0.5g/L of immunoglobulins. Obviously, this indicates that the concentrations of lactoferrin and immunoglobulins in cow’s milk is significantly lower than in human milk.

Lactoferrin is attracting interest for its potential antibacterial and antiviral properties, but the natural levels are grossly insufficient in cow’s milk to have any real impact. Instead, several dairy companies have developed processes to isolate, purify and concentrate lactoferrin from dairy streams so that they can sell it as an ingredient.

We should also be very skeptical of the various outlandish claims used to promote raw milk. I recently heard an individual claim that raw milk contains a bioactive that provides anti-cancer benefits. With health benefits or claims about a product suggesting that it can act like a type of pharmaceutical drug/compound, it is essential that the dose/concentration needs to be sufficient to provide this impact and that the claim should be backed up by solid scientific clinical studies. Milk contains thousands of interesting trace molecules that have no proven or likely physiological impact.

Another claim I have sometimes seen is that raw milk provides enzymes necessary for the digestion of our food. This is not correct as we (humans) have all the digestive systems, including enzymes, and do not need digestive enzymes to be present in milk. The only circumstance that I know of where this might be an issue is preterm babies that may have insufficient lipase activity; because of this possibility, the manufacturers of these specialized formulae include more easily digested fats. Excessive activity in raw milk of enzymes that degrade fats and proteins (i.e., lipases and proteinases) would also cause off-flavors and quality concerns. The type of lipase needed for human digestion of fat is very different to the lipase produced in cow’s milk. Even if pasteurization causes some change in the folding of the whey proteins in milk, that does not have an impact on their digestion.

I have also seen comments claiming pasteurization makes milk highly allergic, which is a strange and false suggestion. For several types of protein allergies, including those for milk and eggs, baking and heating usually reduce the allergic reaction due to denaturation (changes in its folding) of the proteins involved. Some raw milk advocates highlight epidemiology studies (surveys) from Europe that showed a statistical correlation between consumption of farm milk by young children and reduced rates of immune conditions (e.g., asthma and allergies), when compared to children consuming UHT or sterilized milk. However, careful reading of these studies/surveys reveals a much more complex and confusing situation, where in several studies there was little or no statistical correlation in the incidence of these immune conditions when they compared the rates of consumption of boiled farm milk to raw farm milk, or in other studies between raw farm milk to pasteurized milk.

Interestingly, several of these European researchers who have promoted this hypothesis about raw farm milk recently changed their approach and are now studying “minimally processed milk” (which is in fact pasteurized milk), and they are comparing the consumption of pasteurized milk to UHT (sterilized) milk in their latest trial.

They state in their recent studies that the potential protective benefits of milk could also be present in pasteurized milk, but they believe it would be destroyed in sterilized milk. These researchers also state that it is not ethical to feed infants raw milk (due to the possibility that it contains pathogens) even if it provides some immune benefit. If some component of milk can be conclusively demonstrated to provide an immune benefit in children, dairy manufacturers would of course be very interested in fortifying infant formula with sufficient levels of that component to try to provide a benefit to children.

With the recent spillover of the avian influenza virus (H5N1) into cattle, high levels of this virus are found in the milk of infected cattle. Fortunately, pasteurization has been demonstrated to inactivate this virus. Cats that have consumed infected raw milk have become seriously ill, and often this results in death. While humans (like farm workers) do not appear to get serious illness after contacting this virus, there is ongoing concern that there could be a mutation or emergence of a more virulent strain that could be more serious for humans. The virus seems to remain stable for considerable time in refrigerated raw milk from infected cattle.

Recent research indicates that if cheese is made from infected milk, the virus numbers can remain high for an extended storage period. Only in very acidic raw milk cheeses that have pH values of less than 5.0 does the virus appear to lose activity. Fortunately, the use of thermization conditions like heating at more than 140°F for 15 seconds appears sufficient to inactivate the virus. Thermization is the use of a heat treatment that is less than legal pasteurization (which is at least 161°F for 15 seconds). Many producers of cheese made from “raw” milk are in fact using thermization; the regulatory authorities consider heating processes that do not meet the minimum pasteurization conditions to still be raw.

As I look at the loosening of raw milk regulations across the U.S., it is hard for me to think of another example where regulations were deliberately weakened knowing that the overwhelming scientific evidence indicates that this will cause an increased risk of illness in children and sensitive individuals. In a time of confusion and misinformation, we should all strive to make safe dairy products.

CMN

The views expressed by CMN’s guest columnists are their own opinions and do not necessarily reflect those of Cheese Market News®.

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