Student guest post: A Push for Pasteurization

Student guest post by Molly Stafne

Nothing could be worse than watching your seven-year-old lying in a hospital bed fighting for his life after being diagnosed with hemolytic uremic syndrome. Unfortunately, Mary McGonigle-Martin experienced it first hand as her son, Chris, fought for his life after being poisoned by E. coli 0157:H7 found in contaminated raw milk. Like many mothers, Mary was coerced into believing the inaccurate “facts” given to her by the farm she purchased raw milk from. Too often across the US, parents are given incorrect information about the safety of the milk they drink and unfortunately, it is often children that pay the price.

Few people today know of a time when they didn’t have the choice to drink anything but raw milk. Now there is an overwhelming argument that pasteurization is decreasing the nutritional value and safety of the milk. During the 1800s, Louis Pasteur developed the germ theory which claimed that germs outside the body, like those found in raw milk, have the ability to cause infection. As a result, he developed the process of pasteurization which is used in many foods we consume today, including milk, to kill bacteria. In the past couple decades, many consumers have decided that they would rather consume more natural and organic foods rather than those that were produced by more modern methods. It is frequently believed that these natural foods, such as raw milk, are healthier which is not the case.

Pasteurizing milk has had many benefits through history. One of its major contributions is the massive reduction in human tuberculosis cases as the bacteria that causes bovine tuberculosis can also infect humans. Bovine tuberculosis can be spread to humans through contact with an infected animal but most commonly through ingestion of raw milk. Although the prevalence of tuberculosis in humans in the US has significantly reduced since pasteurization began, there are still a number of other zoonotic pathogens that can be transmissible from milk to humans including salmonella, campylobacter, listeria, and E. coli 0157:H7, all of which can have dangerous or unpleasant consequences or even potentially be fatal. E. coli is possibly the most dangerous since it only needs less than 100 organisms to cause infection. It can lead to a dangerous condition called hemolytic uremic syndrome (HUS) which may cause kidney failure. According to the CDC, there have been 148 dairy product-associated outbreaks from 1998 – 2011 that were a result of consumption of raw milk or cheese which resulted in 2,384 illnesses, 284 hospitalizations, and 2 deaths. Today, milk is heated to 161°F for 15 seconds to destroy the bacteria. This is called high temp, short time pasteurization. Another form of pasteurization is low temp, long time, 145°F for 30 minutes.

Proponents of raw milk often argue it has a greater nutritional value than pasteurized milk. There have been numerous studies that have de-bunked this myth according to the CDC. Many factors are involved when determining the nutritional value of a product. One thing that is analyzed is how readily a body breaks down and utilizes a nutrient. If a mineral or vitamin is passed through the body quickly, any loss would be irrelevant. A second analysis would be the percent contribution of the nutrient to the recommended daily intake. If people don’t rely on a certain product as the main source of an essential nutrient, the loss of the nutrient is almost negligible. It is true that some nutrients or enzymes are slightly reduced during pasteurization. For example, lysine is the most relevant essential amino acid found in milk. After heating the milk, only 1-4% loss of the amino acid was observed^1,5,7. But like what was previously alluded to, reduction of nutrients like vitamin C is not considered a significant concern as milk is not a major source of vitamin C. It would take 20 liters of milk to consume the daily requirement of vitamin C, regardless if it was raw or pasteurized milk³. The availability of nutritionally relevant vitamins such as B2 or B12 were found to be affected minimally or not at all by most common heat treatments^2,5. Finally, while milk is a significant source of calcium and phosphorus, neither were affected by heating the milk³.

Another raw milk marketing tool some farmers use is to claim that their cattle are grass fed. When cattle were first domesticated, they were raised on a grass diet. As the understanding of animal nutrition grew, farmers discovered that cattle would gain weight faster if they fed them grain which is economically beneficial. Proponents of grass fed cattle argue that grain is not their natural food and the growth at a faster than normal rate is unhealthy. A grass-fed animal does not mean the animal is healthier. Nutritionally speaking, it was hypothesized that grass fed cattle have a lower milk fat content. The amount of grain does play some role in the fat development but energy and dietary protein intake and the current state of pasture the cattle are being grazed on must also be accounted for. In addition, milk fat content is also determined by the genetics of the individual animal, whether or not it currently has or had infections in her udder, and her stage of lactation³.

In addition, grass-fed cattle don’t necessarily carry a lower bacterial load. Even at the most sanitary facilities, milk is often contaminated by fecal material carrying pathogens during the milking process. According to Dr. Jim Kazmierczak, a Public Health Veterinarian with the Wisconsin Department of Health Services, there have been numerous studies that proved grass-fed cattle shed E. coli 0157:H7 in the feces longer than grain-fed cattle⁴ and that “cattle fed a forage diet were 0157:H7 culture-positive longer and with higher numbers of bacteria in their feces than cattle fed a grain diet.⁶” This means that E. coli 0157:H7 remained alive in their feces longer than grain-fed cattle.  In addition to being found in fecal material, E. coli 0157:H7 can be found where cattle are grazing, can live on different environmental reservoirs for many months, such as gates, walkways, or water troughs, and is found more frequently during the summer.

We are blessed in the US to have a relatively safe food supply. Sure there will be occasional food-borne illness outbreaks but we are fortunate to have the technology, sanitary methods, and capabilities to keep the food we consume free from diseases to the best of our abilities. The invention of pasteurization reduced the number of illnesses and deaths caused by contaminated dairy products while maintaining the integrity and nutritional value of the milk. But there is a misconception of pasteurized milk across the country that has led to people making deadly decisions. Mary McGonigle-Martin would have never given her child raw milk had she known that it had the potential to harm or kill him. The risks are high when consuming raw milk and people need to be properly informed before their put their families and themselves in unnecessary danger.

1. Andersson, I., and Öste, R. (1995). Nutritional quality of heat processed liquid milk. In P. F. Fox (Ed.), Heat-induced changes in milk (2nd ed.) (pp. 279e307). Brussels: International Dairy Federation.

2. Burton, H. (1984). Reviews of the progress of dairy science: the bacteriological, chemical, biochemical and physical changes that occur in milk at temperatures of 100e150 _C. Journal of Dairy Research, 51, 341e363.

3. Claeys, W. L., et. Al (2013). Raw or heated cow milk consumption: Review of risks and benefits.

4. Hovde, C. J., et al. (1999). Effect of cattle diet on Escherichia coli O157:H7 acid resistance. Appl Environ Microbiol 65:3233–32

5. Schaafsma, G. (1989). Effects of heat treatment on the nutritional value of milk. Bulletin of the International Dairy Federation, 238, 68e70.

6. Van Baale, M. J., at al. (2004). Effect of Forage or Grain Diets with or without Monensin on Ruminal Persistence and Fecal Escherichia coli O157:H7 in Cattle. Appl Envir Microbiol 70:5336-5342.

7. Walstra, P., and Jeness, R. (1984). Dairy chemistry and physics (p. 467). New York: John Wiley & Sons.