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Raw milk: risk vs. benefit

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®.

The everyday, safe and nutritious glass of milk is often taken for granted. After all, it has been more than 100 years since Chicago, in 1908, became the first U.S city to introduce cow’s milk pasteurization into municipal law (except for cows that were certified tuberculosis-free). Other cities soon followed their example and in 1924 the U.S Public Health Service developed a regulation known as the Standard Milk Ordinance for voluntary adoption by state and local agencies; this is now called the Grade “A” Pasteurized Milk Ordinance (PMO) and it has helped to make milk a safe and nutritious product that is enjoyed by millions daily.

According to the PMO, in 1938 milkborne outbreaks constituted for 25 percent of all disease outbreaks due to infected food/water. Today milk and fluid milk products account for less than 1 percent of such reported outbreaks. According to a report (The Pasteurization of Milk) published by G.S. Wilson in the British Medical Journal (1943), between 1912 and 1937 about 65,000 persons in England and Wales died of tuberculosis of bovine origin. Wilson (writing in 1943) also states that “a few years ago, owing to insufficient evidence, scientific opinion was divided on pasteurization. Since then numerous experiments have been carried out in the laboratory and in the field, the results of which show that pasteurization brings about no detectable change of any significance in the nutritive value of milk. Objections are frequently raised to it on pseudo-scientific grounds.”

Today, his conclusions remain as true as they were in 1943. While pasteurization of milk is often hailed as one of the greatest ever public health achievements, many groups are still actively promoting the sale of raw milk. While some of the diseases routinely transmitted by milk a hundred years ago have been reduced, other pathogens have emerged. This is a concern for the dairy industry and the public as milk is not a sterile product. As the past shows, unpasteurized milk can be a dangerous and even fatal product should harmful pathogens be present.
Raw milk advocates continue to argue that pasteurization destroys many of the beneficial properties of milk. For example, advocates claim that enzymes in raw milk may aid in digestion and that the heat involved in pasteurization eliminates the nutritional value of milk. In the most recent study regarding health benefits and risks of raw milk, researchers noted that there was no significant difference between raw and pasteurized milk in regards to nutrition.

“Raw or Heated Cow Milk Consumption: Review of Risks and Benefits,” published in Food Control, September 2012, states “(native) milk enzymes hardly contribute to the digestibility of milk. Moreover, most milk enzymes are destroyed in our (human) digestive system by pepsin and/or gastric pH.” Additionally, the study states that “common pasteurization conditions have no significant effect on the lactose level” and thus would have no impact on lactose intolerance. Pasteurization has only a minor impact on vitamin levels. Some raw milk contains beneficial probiotic bacteria but much less than the very high numbers (millions) that would have to be ingested to possibly gain any health benefit. Some claim that raw milk somehow prevents the growth of pathogens; unfortunately, pathogens can grow well in this rich medium. Some claim that drinking raw milk provides some type of protective immunity effect, but there is no scientific evidence to support this idea. Based on this review and many others like it, there is NO proven scientific benefit to the consumption of raw milk. In fact, there are many studies and statistics showing the dangers of raw milk consumption.

Pasteurization, particularly high-temperature, short time (HTST), destroys harmful pathogens such as Listeria, Salmonella and E.coli, preventing them from causing foodborne illness. HTST heats raw milk to 161 degrees Fahrenheit for a minimum of 15 seconds before the milk is cooled to 45 degrees Fahrenheit. This fairly simple and quick process can eliminate the harmful pathogens from milk while leaving most nutrients intact. This is a similar concept to cooking raw meat or eggs before consumption, as this process of heat-treating eliminates many of the most harmful bacteria and greatly reduces the risk of foodborne illness. In fact, according to the Center for Disease Control, between 1993 and 2006, 60 percent of all dairy-related outbreaks reported to the CDC were related to raw milk. Additionally, 75 percent of those outbreaks were in states where it is legal to sell raw milk.

Remember that even extremely clean and well taken care of cows can succumb to mastitis, a common bacterial infection of a cow’s udder. There are at least four different sources by which raw milk might become contaminated by pathogens: direct passage from the blood (of the cow) into milk (systemic infection), mastitis (udder infection) and fecal contamination (external contamination of milk during or after milking) or contamination from skin. Pathogens are not visible to the naked eye and measurements of their numbers can take several days to complete, so it can be extremely difficult to determine the safety of raw milk before that milk has been consumed. Occasional testing of raw milk does not guarantee that pathogens are absent from the milk supply on days when no testing is done (e.g., due to contamination during milking). This makes the consumption of raw milk an extremely risky behavior, especially to those with compromised immune systems or for the young, pregnant women and the elderly. Fortunately, these pathogens are destroyed by pasteurization.

Finally, it is important to note the distinct differences between raw milk and a raw milk cheese. FDA does allow for the sale of raw milk cheeses in the case of certain varieties, which must be aged for 60 days at 35 degrees Fahrenheit. The specific rules and regulations regarding this measure can be found under the Code of Federal Regulations, Title 21, Part 133. Several studies have shown that certain varieties of raw milk cheese (e.g. Cheddar) can be safe for consumption when manufactured under hygienic conditions, but 60 days in the safe temperature range does not guarantee a safe product for all cheese types. Cheeses with a pH over 6 should not be manufactured with raw milk. Additionally, pathogens can survive even in a raw milk cheese with a pH under 6 if proper manufacturing (and sanitation) measures are not taken. So, it is critical that raw milk cheeses be made with the highest quality milk and that extreme care is taken during manufacture and beyond. Recently, FDA estimated that soft cheeses made with unpasteurized milk were between 50 to 160 times more likely to cause a Listeria infection than when these cheeses were made with pasteurized milk (Listeria can grow at refrigeration temperatures and has a relatively low infective dose).

Overall, it’s important to remember that many food products have the potential for foodborne illness. Pasteurized dairy products have a lower incidence of foodborne illnesses and if there is an issue it is often caused by a post-pasteurization contamination issue such as poor sanitation. Raw milk, however, has a history of causing foodborne illness, and there is no peer-reviewed science suggesting a significant benefit to consuming raw milk vs. pasteurized milk. Consumer interest in less processing of foods (or raw foods) is one factor encouraging raw milk sales but such a serious decision requires an unbiased risk vs. benefit analysis. It is up to scientists and the regulatory agencies to educate themselves and the public on the importance of protecting our food supply and maintaining a trusted reputation. Why repeat the tragic mistakes of the past?

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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