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The Dose Transcript for December 5, 2024

Host: Dr. Brian Goldman

BRIAN GOLDMAN: Hi, I'm Dr. Brian Goldman. Welcome to The Dose. Well, a lot of people seem to be talking lately about raw, unpasteurized milk. California is currently issuing warnings about consuming raw milk after bird flu was detected in two lots of unpasteurized milk. And that story, of course, is changing as we go. But those and other warnings come as raw milk proponents, most notably Trump nominee for Health and Human Services Secretary, RFK Jr., say that we should be consuming unpasteurized milk. So this week we're asking: What is the risk of drinking raw milk? Hi, Lawrence. Welcome to The Dose.

LAWRENCE GOODRIDGE: Thank you.

BRIAN GOLDMAN: As an observer, as a researcher, what is the public's fascination with raw milk that seems to come up every once in a while?

LAWRENCE GOODRIDGE: The public's fascination with raw milk, I think, is part of a broader fascination or interest in consuming natural foods. The thought is that food should be consumed in its natural form. So with respect to consumption of raw milk, proponents of that consumption would say that any change to the milk -- typically through heat, through pasteurization -- would lead to deleterious effects, and that consuming raw milk is much more healthy than consuming pasteurized milk.

BRIAN GOLDMAN: So that's kind of the meta message of our conversation. This is a really important one because periodically we need to remind people about potential risks. Before we begin, though, can you give us a hi, my name is? Tell us what you do and where you do it. Just ad lib.

LAWRENCE GOODRIDGE: My name is Lawrence Goodridge. I am a professor of food safety at the University of Guelph. I also direct the Canadian Research Institute for Food Safety at Guelph, and I'm also a Canada Research Chair in Foodborne Pathogen Dynamics, where I study all aspects of food-borne illness caused by harmful bacteria.

BRIAN GOLDMAN: Clearly we're going to be getting into that subject in a big way in just a moment. As a physician, I know that pasteurization kills bacteria contained in raw milk. What precisely is required to say that milk has been pasteurized?

LAWRENCE GOODRIDGE: Pasteurization is a process that we can trace back to 1861. The French chemist Louis Pasteur conducted some experiments where he proved a concept known as germ theory. He subsequently invented a process -- pasteurization -- by which bacteria could be killed by heating beverages -- in his case, it was wine -- between 60 and 100 degrees Celsius and then letting it cool. And so he then went on to patent this pasteurization process and it was applied to various liquids -- beer, juice, liquid eggs, and most famously, milk. The pasteurization process that we use today is directly descended from that invention, where we heat liquids -- you know, we're talking about milk today, but, you know, juices and other liquids -- to 72 degrees for 15 seconds or 63 degrees for 30 minutes. And both of those treatments are equivalent.

BRIAN GOLDMAN: When did pasteurization come to Canada, more or less?

LAWRENCE GOODRIDGE: Pasteurization in Canada can be traced back to 1927, where there was an outbreak of typhoid, which is caused by a bacteria called salmonella. And this outbreak occurred in Montreal and was caused by contaminated milk. And then in 1938, so approximately 10 years after, 11 years after that outbreak, the province of Ontario became the first Canadian province to ban all sales of raw milk.

BRIAN GOLDMAN: As you said off the top, part of this popular trend to consuming unpasteurized milk comes from the notion that the less adulterated the milk is, the better it is, the healthier it is, the greater nutritional value that it has. Is there also a kind of anti-science bias that if scientists play with something like milk or do something to milk, or if there's a process that required a scientific method and it involved research by scientists, that somehow that makes the milk worse than it was before in its unadulterated state?

LAWRENCE GOODRIDGE: I think that I certainly would hesitate to paint everybody who supports the consumption of raw milk with the same brush. There's a variation in thoughts or reasons as to why people consume raw milk. That said, part of that population of proponents for raw milk consumption, in my opinion, do so because of this backlash against science. This really shows up with respect to comments about illnesses caused by consumption of raw milk. Certainly, in discussions I've had with some people, that data tends to be minimized or not even accepted. For those people then, any such studies that would show, for example, that nutrients in the milk, vitamins and minerals and so forth, are not damaged by the pasteurization process, which is a relatively mild treatment, those people who are not really listening to scientific facts would discredit or just ignore those facts.

BRIAN GOLDMAN: When you were talking about the history of pasteurization in Canada, you talked about typhoid, a salmonella typhi outbreak in Quebec, in Montreal. So bacterial infections are one of the major risks of consuming raw, unpasteurized milk. What's the range of bacteria that we know about that could potentially infect the milk?

LAWRENCE GOODRIDGE: Animals harbour a wide array of microorganisms that can cause disease in humans. These are called zoonotic pathogens, meaning that they can cause disease in the animals themselves, but can be transmitted to humans. And one of the main routes that these microorganisms can be transmitted is through food. Microorganisms get into the milk during the milking process because they are present in the animal. They're certainly present on the hides of the animals through, you know, manure. And so in terms of specific pathogens, ones that many people would have heard of recently if they've been paying attention to the many outbreaks and recalls that have occurred. So E. coli, and specifically a certain type of E. coli known as E. coli O157:H7, which is a very serious pathogen, causes very serious illness, including systemic diseases and even death. And then there's salmonella, which we've talked about already. Listeria. At the top of this talk we're having today, you mentioned the current situation in California, where bird flu, influenza H5N1, has been found in raw milk, leading to a complete cessation of sales of raw milk from that particular producer in California. And I could go on. We certainly know that there are a number of pathogens that cause illness if one were to consume raw milk.

BRIAN GOLDMAN: All that said, every time you drink, you consume raw unpasteurized milk, you risk those bacterial infections. That doesn't mean it's going to happen every time you drink it, am I right?

LAWRENCE GOODRIDGE: You're exactly right. So now we're talking about the concept of risk. And I think this is where people oftentimes become confused. What we're seeing is if one consumes raw milk, the risk of becoming sick with a food-borne pathogen is much higher than if one were to consume pasteurized milk. That does not mean that every time one consumes raw milk, they'll get sick. So the analogy that I like to use is driving a car and speeding. So we know that driving above the speed limit is a very risky behaviour. It could result in car crashes and so forth. But that doesn't mean that every time somebody speeds, they will get into an accident. But the risk of getting into an accident certainly increases if one speeds. And so it's the same with the consumption of raw milk.

BRIAN GOLDMAN: You mentioned E. coli O157:H7, and I remember being a resident at SickKids in Toronto when there was an outbreak of that particular type of E. coli. Explain why unpasteurized milk is particularly harmful to young children.

LAWRENCE GOODRIDGE: There are certain high-risk populations who are at higher risk of obtaining a food-borne illness. And so that includes children, it includes the elderly, it includes pregnant women, and it includes those with compromised immune systems. And the reason why these populations are at higher risk is for the same reason, and it has to do with their immune system. So in children, the immune system is not fully formed yet. In the elderly, the immune system is breaking down. In pregnant women, the immune system is suppressed because of the tissue that is coming from a foreign body that is the father. So the fetus is made up of tissue from the mother and the father, and if the immune system was not suppressed, the body would actually attack that tissue and kill the fetus. So, the immune system's suppressed. In people with underlying diseases like tuberculosis or cancer or AIDS, their immune system is under attack and is not functioning properly. And so what this means is when one from one of those groups is exposed to a pathogen, they have trouble fighting it off or may not be able to fight it off, as would be the case for a healthy person. And so with the case of children, an E. coli O157:H7 is particularly devastating in children. It causes typical food-borne disease symptoms -- diarrhea and vomiting, severe abdominal cramps. But this particular pathogen produces toxins, which can attack the red blood cells and the kidneys. And so, one of the main symptoms of E. coli O157:H7 infection is gross bloody diarrhea, which can progress to kidney disease. If the kidney disease is serious enough, the patient requires dialysis, which could be lifelong. Or if it's more serious than that, the patient then requires a kidney transplant or they will die. And in some cases, nervous system complication can arise as well.

BRIAN GOLDMAN: We're doing this topic in the context of H5N1 avian flu being detected in a growing number of dairy farms in the U.S. I think people listening to this want to know what viruses can be detected in raw unpasteurized milk, and I guess more important, does pasteurization deactivate the virus?

LAWRENCE GOODRIDGE: Raw milk can contain a number of viruses, but any virus that an animal might have that can be transmitted to humans could be found in the milk. So it's important to understand that pasteurization will kill all pathogens that can cause illness in humans, whether they're bacteria or viruses. However, it's also important to understand that pasteurization does not produce sterile milk. It's a very mild heat treatment. This is why vitamins and then other nutrients and minerals, for example, are not damaged with the heat treatment. It's not like we are sterilizing milk, like how we would use the type of heat that we would use to produce canned products, for example. That's not what pasteurization is. It's a very mild form of heat. And so what this means is there are still bacteria that are living in the milk. Those bacteria that are living, however, will not cause human illness. They will spoil the milk. So this is why if you buy milk and you take it home and you put it in the fridge, even if you never open it, the milk will still spoil because there are bacteria, spoilage bacteria, that will grow and spoil the milk.

BRIAN GOLDMAN: Kind of adjacent to what you're talking about, there are a lot of misconceptions out there about the so-called benefits of consuming raw milk versus pasteurized milk. The first of those would be that somehow the pasteurization process reduces the nutritional value of the milk.

LAWRENCE GOODRIDGE: Absolutely. There's several claims that are often trotted out with respect to why raw milk is supposedly superior to pasteurized milk with respect to nutrition. For example, one of the main ones is nutrients. So proteins, minerals, vitamins like vitamin C and vitamin B and so forth, become inactivated during pasteurization, but not in raw milk. So this is one reason why proponents would say that we should drink raw milk. Scientific studies show that that's not the case. Pasteurization does not cause any change in the quality of proteins. Certainly, studies have shown that there is a small amount of denaturation. That means that proteins break down. Less than 7% [indistinct] protein called whey protein that has been reported due to pasteurization. But this does not affect their nutritional quality. Same thing with vitamins. Pasteurization can cause very minor losses. Less than 10% of certain vitamins -- vitamin C, vitamin B9 and B12 and B6, for examples. But it's important to know that of these vitamins, milk is an excellent source of only vitamin B12, and it has very low concentrations of most of the other vitamins that we've discussed. And pasteurization does not change the concentration of other vitamins like riboflavin, which is very heat stable. Or fat-soluble vitamins like vitamin A or vitamin E. So the pasteurization process does not really change that. Others have said, well, what about allergies? So there's a allergic reaction to what is called cow's milk allergy or CMA, which is a human immune system reaction to proteins found in cow's milk. Two of the proteins, typically casein and whey. When someone with CMA consumes milk or milk-based products, their immune system mistakenly identifies these proteins as harmful invaders. They think there's some kind of infection, so it triggers an allergic response. And so symptoms can range from mild reaction, like skin rashes and hives, to severe: swelling, difficulty breathing and anaphylaxis. And CMA is most common in young children and infants, but many outgrow this as they age. So the thought is that there would be less or even no cow's milk allergy if one consumes raw milk. But that, again, is not shown. Raw milk does not help with the cow's milk allergy. Both raw and pasteurized milk can trigger the allergic reactions in individuals. And if we move down to lactose intolerance, again, the thought is that raw milk would help with lactose intolerance because lactase, the enzyme that is used to break down lactose, which is a sugar commonly found in milk, the thought is it's more active in the raw milk than the pasteurized milk because it's not been heated. But there's no scientific evidence that supports that. And then there's several other claims that because pasteurization kills bacteria, that we're not getting the natural bacteria that would be present in raw milk and so we should consume raw milk. And that would include things like probiotics, for example. So again, it's important to understand that pasteurization does not kill all bacteria. So there's still living bacteria present. It only kills the pathogens. But probiotics are often added to milk-based foods like yogurts after the fact. And so any concerns about that are alleviated.

BRIAN GOLDMAN: Okay, so just to summarize some of the myths that you went through one by one. Unpasteurized milk does not contain some magical probiotic characteristics that are not present in pasteurized milk. Lactose intolerance is the same whether it's pasteurized or unpasteurized milk. And milk or cow's milk allergy, if you're allergic to the components of cow's milk allergy in pasteurized milk, you'll also be allergic in unpasteurized milk. Have we got that right?

LAWRENCE GOODRIDGE: That's right.

BRIAN GOLDMAN: Good. Raw milk proponents also say that consuming unpasteurized milk can reduce asthma. What do we know about that?

LAWRENCE GOODRIDGE: Yeah, again, there's not a lot of scientific evidence or any scientific evidence to really demonstrate that. I will say this. Raw milk proponents, many of whom who I talked about this with, live in rural areas. And oftentimes, you know, there'll be anecdotal stories: Well, my friend lived on a farm and drank raw milk all their lives and they've never gotten sick. Or, I drank raw milk living on a farm and I never got sick. So now, you know, I give it to my kids. So there is something to that in comparing, you know, rural populations to urban populations. So people who live on farms -- and certainly there's scientific evidence to support this. People who live on farms are exposed to, you know, a number of bacteria and so forth. Certainly, if they were breastfed from their mother who also lived on a farm, they were able to get antibodies. And so they likely have more protection against these pathogens than the people who live in cities and who were never exposed. So there is something to that. It doesn't mean that one should consume raw milk. There's still risks. You know, we talked about the high-risk populations. And even so-called healthy people, if they have an underlying health condition that they don't know about, they could be more susceptible to pathogens. So still not a good idea, but there is certainly an aspect of that.

BRIAN GOLDMAN: But based on what you've said, it would be very hard to tease out all of the other potential factors that could be contributing to the incidence of asthma occurring in kids, for instance, who live in rural parts of the country. And consuming raw milk would not be the sole factor in that kind of analysis. Health Canada does not permit the sale of unpasteurized milk, but what about unpasteurized cheese?

LAWRENCE GOODRIDGE: Selling raw milk in Canada is illegal. The sale of cheese made from unpasteurized milk is allowed, or is legal, as long as the cheese has been aged at 2 degrees Celsius or above for at least 60 days. And that's because the aging process will destroy any pathogens that are present in that cheese.

BRIAN GOLDMAN: Last question I want to ask you. Is there any alternative process aside from pasteurization that makes raw milk safe for human consumption?

LAWRENCE GOODRIDGE: Well, there's certainly no process that is allowed or regulated. Pasteurization remains the only process that, by law, can be used to treat milk. That said, there are a number of other processes that have been investigated for other liquids. One that I think holds promise. These are non-thermal processes. So one particular method that I think holds promise and would be very interesting to apply to milk is high hydrostatic pressure. There is a commercial process that's been developed. And so it allows for liquids and other foods to be treated with this pressure, which kills the microorganisms but does not damage food or the liquid. In my opinion, that's one potential method that could be applied to raw or unpasteurized milk. And studies, you know, should be done to see if that would also be an equivalent treatment to pasteurization. And this may help those who are against pasteurization. Because one of the supposed advantages of raw milk that people who drink it will say is that it tastes better than pasteurized milk. Taste is a very subjective thing. I don't know that there's any evidence to support that. But given the fact that the other liquids, when this high pressure was applied, consumers were not able to determine any differences in taste. So this may be one way to alleviate that concern with raw milk.

BRIAN GOLDMAN: Lawrence Goodridge, you know, you know a lot about this subject. And, you know, I'm amazed and gratified to know that there's so much to know about the pasteurization process and alternatives to pasteurization and all the implications when it comes to milk, both in terms of benefits and the risk of consuming raw unpasteurized milk. And I want to thank you for coming on The Dose to talk about it.

LAWRENCE GOODRIDGE: Thank you very much.

BRIAN GOLDMAN: Lawrence Goodridge is a professor of food safety at the University of Guelph. He's director of the Canadian Research Institute for Food Safety and holds a Canada Research Chair in Foodborne Pathogen Dynamics. Here's your dose of smart advice. Pasteurized milk is raw milk from dairy animals that has been heated to either 63 degrees Celsius for 30 minutes, or 71 degrees Celsius for 15 seconds before cooling. The idea is to kill bacteria found in raw milk that are harmful to humans. These include Campylobacter, E. coli O157:H7, salmonella, Listeria, and others. Pasteurized milk prevents bacterial infections and saves lives. Infection with these and other bacteria can cause food poisoning. The symptoms can be mild, but can also cause serious illness. Children infected with E. coli O157:H7 can develop hemolytic uremic syndrome, which is life-threatening. Pregnant women infected with Listeria are at greater risk of miscarriage as well as illness and death of newborn babies. Viruses have also been detected in unpasteurized milk. Bird flu, also known as H5N1 influenza, was first confirmed in U.S. dairy cattle in March 2024 and has been spreading widely, especially in California. High levels of the virus have been found in the milk of infected cows. Pasteurization kills viruses, including H5N1. Pasteurizing milk does not lead to lactose intolerance and does not strip raw milk of its nutritional value. Both raw and pasteurized milk trigger allergic reactions in people who have an allergy to milk proteins. Raw milk is not probiotic and does not reduce the likelihood of asthma. Some people believe that it's safe for them to consume raw milk because they grew up consuming it and never got sick. But a serious infection can occur at any time. In Canada, all milk sold to the public must be pasteurized and packaged in a licensed dairy plant. Only vitamins A and D may be added to the milk for health benefits. A 2022 U.S. study found that jurisdictions that permit the sale of unpasteurized milk have 3.2 times the number of dairy-borne outbreaks compared to those that don't permit it. State laws that result in increased availability of unpasteurized milk are associated with more outbreaks and more illnesses. If you do consume raw milk, see a health-care provider if you get symptoms of food poisoning. They include: vomiting, diarrhea, abdominal pain, plus flu-like symptoms such as fever, headache, and body aches and pains. These warnings are especially true for kids and for pregnant women. If you're pregnant and believe you may have consumed raw milk products, see a health-care provider immediately. Butter and cheese made from raw milk is safer to consume because the fermentation and production process kills some harmful pathogens. However, unpasteurized butter and cheese must be aged before it can be sold in Canada. Finally, pasteurization does not mean that it's safe to leave milk out of the refrigerator for extended time, particularly after it has been opened. If you have topics you'd like discussed or questions answered, our email address is thedose@cbc.ca. If you liked this episode, please give us a rating and review wherever you get your podcasts. This edition of The Dose was produced by Sameer Chhabra. Our senior producer is Colleen Ross. The Dose wants you to be better informed about your health. If you're looking for medical advice, see your health-care provider. I'm Dr. Brian Goldman. Until your next dose.

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What's the risk of drinking raw milk? - Transcript

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