Public Health Mythbusters Edition: Raw Milk, Friend or Foe?

The last twenty years have not been kind to Louis Pasteur. He ordered that his laboratory notebooks be withheld from outsiders, but in the 1970’s one of his heirs left them to the Bibilotheque Nationale in Paris. In the mid-1990’s a researcher from Princeton went through the notebooks and then wrote a book on what he found. Since then embarrassing revelation after embarrassing revelation have come to light. In the race for an anthrax vaccine, Pasteur took his rival’s technique, misrepresented it to the public as his own, lied to get published and subsequently obtained a monopoly on the manufacture of all anthrax vaccine at the time. (The rival, a veterinarian named Toussaint, was so devastated by the theft of his work that he suffered a nervous breakdown and died shortly thereafter.) In the famous story of Pasteur administering a rabies vaccine to a boy who had supposedly been bitten by a rabid dog, Pasteur claimed that his vaccine had been tested on 50 dogs without a single failure. And that was true- but not for the vaccine he administered to the boy. That one was prepared in a different way and Pasteur had no conclusive evidence to show that it would work. Now, a small but growing group of people are questioning how effective and beneficial the treasured process of heating drinks and food to kill bacteria that bears Pasteur’s name really is.

Since my husband is Superman and milk of any kind has  proven to be his kryptonite, we don’t drink any animal milk at all any more. However, the question of pasteurized versus raw milk has intrigued me. I had heard since I was child that pasteurization was one of the greatest innovations in public health. All the milk I drank as a kid was pasteurized. On the other hand, my grandparents and great-grandparents were raised in small farm communities in Southern Canada . The kind of place where fifty years ago you could walk around the neighborhood and see a housewife out plucking a chicken for dinner that evening. The kind of town where cows outnumber people and the horizon is broken only by a lonely grain elevator.  And the people who lived in these small farming towns drank raw cow’s milk all. the. time. My dad lived in one of these towns for a few years  as a kid and recalled picking up buckets of fresh cow’s milk from his grandfather in the bone-chilling prairie winter nights.

My dad never got sick from drinking raw milk. My grandparents never got sick from drinking raw milk. My great-grandparents never got sick from drinking raw milk. But history tell us that a lot of people did get sick from drinking raw milk. And the news media continues to tell us today of incidents of people (including pregnant women and children) getting really, really sick from drinking raw milk. So what gives? What is it about raw cow’s milk that makes people (sometimes) sick?

Cow’s milk itself is generally not the problem. In fact, some sources say that milk straight from a healthy cow is sterile. This is most likely why my great-grandparents never got sick from drinking raw milk. They owned a few cows which grazed on their land, milked them and used it right away. When your milk distribution process is picking up a bucket from the barn where only a few cows have been, you have much greater control over the sanitation of the cows and milking. It’s the process of milk distribution and dairy farming that create the contamination problems most of the time. The soil, manure, feed, insects  and workers on the dairy farm can all cause pathogens to get into the milk and cause contamination. If an animal has mastitis, the bacteria that caused the infection can shed into the milk as well.

For large-scale dairy farms, pasteurization is a necessity because monitoring the health and sanitation of so many animals and their environment is extremely difficult. Another reason pasteurization is necessary for large scale dairy farms is that the milk from these farms is typically shipped out across the country to large grocery stores, and thus needs to have a longer shelf-life. In the 1940’s, reports indicate that milk had a shelf-life of 3-7 days, now it has an average shelf-life of 14-21 days, often longer. Part of this long shelf-life is due to a reduction in the number of pathogens by pasteurization. But the other place that contamination can occur is in the processing plant. And in fact, this is where things can get scary with pasteurized milk.

Post pasteurization contamination (commonly abbreviated PPC) remains a significant concern for the dairy industry. There are types of contaminants called psychrotolerant sporeformers that can survive the high temperatures of pasteurization and then flourish in refrigeration. These nasty organisms can cluster in groups on the processing equipment and create a biofilm that protects the spores from heat and chemical sanitization agents. In fact, the largest outbreak of salmonella in American history occurred in the mid 1980’s and involved pasteurized milk from a single dairy plant. The number of people affected was estimated to be between 168,791 and 197, 581. The salmonella strain was found to be antimicrobial resistant. And cases of food poisoning involving pasteurized milk products are still frequently reported. So in all reality, any of those cartons of pasteurized milk you see in the grocery store can be crawling with disease causing microbes.

That being said, raw dairy products caused 42 of the 56 dairy related outbreaks between 2000 and 2007, most of which were caused by campylobacter pathogens.  (See pages 18-19 of cited pdf for the following statistics.) There were two large outbreaks of campylobacter outbreaks with pasteurized milk, but these occurred at prisons with on-site dairies that had PPC problems, not milk sold to the general public. For the other pathogens (e. coli, listeria and salmonella) the results were more mixed. Between 2000 and 2007, there were 5 raw milk e. coli outbreaks and 1 related to queso fresco soft cheeses with none related to pasteurized milk. For listeria, there were 3 outbreaks related to soft cheeses and 2 related to pasteurized milk with none related to raw milk. For salmonella, there were actually 4 pasteurized milk related outbreaks, 3 raw milk related outbreaks and 1 case related to soft cheeses. Some sources say that consuming raw milk increases levels of “good” bacteria in the body, which could potentially fight bad bacteria.

However, dairy products both raw and pasteurized account for the smallest number of the foodborne illnesses for any  category of food (page 10). This chart from the CDC (which unfortunately groups eggs and dairy together) shows that produce, meat and poultry cause far more cases of foodborne illness and death than any type of dairy products. So statistics seem to show that you are much, much more likely to develop a serious foodborne illness from melons, spinach, chicken or beef than any kind of milk.

Whether raw or pasteurized, sanitation issues remain the biggest issue with the safety of dairy products. Raw dairies that have been sources of outbreaks typically have issues with sanitation, but pasteurized milk dairies and processing plants that have been sources of disease often have the same problem. Another problem with raw dairies is outsourcing, as was the case of a California dairy farmer who started buying and then selling colostrum from surrounding dairies that were not licensed to sell raw milk. The unlicensed colostrum ended up causing an outbreak of e. coli. But no matter where you get your milk (raw or pasteurized) you want it to come from a sanitary dairy and plant.

Are there benefits to raw milk? When my oldest was in the NICU recovering from surgery, I found out that NICU nurses used to warm breast milk in the microwave, until it was found that the babies didn’t thrive on microwaved milk. Similarly, heating milk to high temperatures does alter its composition. It kills off beneficial microorganisms and enzymes. But that is the idea behind pasteurization is to kill off all microorganisms. Research from Europe shows that raw milk consumption may lead to decreased levels of allergies and asthma. Raw milk also typically comes from small, local dairies that use more traditional farming practices such as allowing animals to graze in pastures for most of their time. The conditions on these farms can be healthier for animals than the crowded conditions of corn-fed dairy cows. (If you want to find out more about this, watch Food Inc.)

So if you want to drink raw milk, having a cow might be best- if you have the pasture to graze it in! However, if you’re thinking about getting milk from a local raw milk dairy, it would be extremely wise to find out as much as you can about the sanitation practices of the dairy and find out if they outsource any of their products. And if you drink pasteurized milk, hope that you didn’t get one of those gallons that was in contact with bio-film covered equipment.

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