What Are The Risks Of Drinking Raw Milk?

RACHEL FELTMAN: This is Science Friday. I’m Rachel Feltman. Social-media influencers can have a big influence on what people buy, what they listen to, and sometimes even what they consume. For instance, on platforms like TikTok, Instagram, and Facebook, you may have seen influencers touting the benefits of raw milk.

SPEAKER 1: It’s definitely been popping up more on my feed recently.

SPEAKER 2: This is why you should be drinking raw milk.

SPEAKER 3: I love raw milk.

SPEAKER 4: I drink raw milk every day.

SPEAKER 5: The reason that we love buying dairy from the Amish is that they don’t pasteurize their dairy.

SPEAKER 6: Let’s talk about my raw milk consumption.

RACHEL FELTMAN: In a 2022 study, just over 4% of Americans said that they had consumed raw milk in the past year. That might not sound like a lot, but it adds up to around 15 million people, and those numbers seem to be increasing. According to data from the market-research agency NielsenIQ from May, sales of raw milk are up by almost 65% compared to this time last year.

But despite what some celebrities might be claiming, raw milk is not completely safe to drink. It’s more likely to contain dangerous pathogens than pasteurized milk, and that can mean the sort of bacteria that can give you food poisoning. Just last week, more than 150 people in California were infected with salmonella from raw milk, marking the largest outbreak in the past decade linked to unpasteurized dairy.

But raw milk can also expose you to viruses. The CDC recently reported that dairy cows in 13 states were infected with the H5N1 virus, also known as bird flu. And several studies have shown that when sick cows get milked, their bird flu can go along for the ride. It’s an example of how, when it comes to health information and misinformation, it’s important to find sources you can trust.

Here to tell us more are my guests, Dr. Celine Gounder, editor at large for public health at KFF Health News and infectious-disease specialist, and Dr. Nicole Martin, assistant research professor of dairy foods microbiology at Cornell University. Thank you both so much for joining me.

CELINE GROUNDER: Great to be here.

NICOLE MARTIN: Thanks for having me.

RACHEL FELTMAN: Dr. Gounder, let’s start with the big picture. Where did this trend of drinking raw milk come from, and how has it gotten widespread enough to show up on so many people’s social media feeds?

CELINE GROUNDER: Well, I think we’ve seen this surge in popularity with raw milk connected to the H5N1 bird-flu outbreak among cows. And I think whenever you see something new, something where there might potentially be a political angle on it, you’re going to see people come up with mis- and disinformation around it.

I think there’s a lot of appropriate concern about overly processed food and wanting healthier alternatives, right? But having food that is appropriately cooked, heated, refrigerated, frozen, that’s really not about processing. It’s about keeping food safe and healthy.

RACHEL FELTMAN: Yeah, I definitely want to get more into those valid concerns in a minute. But first, Dr. Martin, what are the differences between pasteurized and unpasteurized milk? Basic question I know, but fill us in.

NICOLE MARTIN: Absolutely. So pasteurization, as you might know, has been around for quite some time. This is a gentle heat treatment that is designed specifically to kill the most heat-resistant pathogens that are found in raw milk.

So raw milk is as it comes from the cow or the farm. It has not been processed in any way. And that pasteurization is conducted at a couple of different temperatures, but here in the United States, we primarily use what’s called high-temperature, short-time pasteurization, which is a very, very brief heat treatment. It’s 162 degrees Fahrenheit for 15 seconds. So very quick, but it is effective at eliminating those pathogens or bacteria that can make people ill.

RACHEL FELTMAN: And I know that it’s a common refrain from raw-milk fans that unpasteurized dairy retains certain health benefits that don’t make it through pasteurization. Is there any truth to that at all?

NICOLE MARTIN: There’s really not. So I hear this a lot from various folks, and there’s a lot of belief systems to that idea that raw milk is, in some way, healthier than– nutritionally healthier than pasteurized milk. But the reality is this is a very mild heat treatment. It has very minimal impact on the constituents of the milk itself. There’s lactose in raw milk, and there’s lactose in pasteurized milk. There’s protein in both. We see some very minor decreases in certain heat-labile or heat-sensitive enzymes but nothing to the degree that would confer a health benefit by drinking the raw milk.

RACHEL FELTMAN: And when we’re talking about the risks of drinking unpasteurized milk, What types of pathogens are we talking about? and what kinds of problems can they cause?

NICOLE MARTIN: Well, as you mentioned earlier in the segment, salmonella is one. We also know that listeria, E. coli, campylobacter, that’s a very common pathogen that we see causing outbreaks in the United States from raw-milk consumption. So there’s a whole host of pathogens that we can find naturally in raw milk, and those cause varying degrees of illness in humans.

So campylobacter, it’s unpleasant. Nobody wants to get it. People would probably think, oh, I’ve got some sort of flu or gastrointestinal thing. But then on the other end of that spectrum, we have a pathogen like listeria, which has a mortality rate of 15% to 20%. So folks who get ill with that pathogen, a lot of them die.

And so that’s certainly much more serious, right? And we can’t tell just by looking at an animal or looking at a farm or looking at the milk itself if these harmful bacteria are present or not.

RACHEL FELTMAN: Am I remembering correctly that listeria is particularly dangerous for pregnant people too?

NICOLE MARTIN: That’s right. And that’s why there are guidelines about eating things like soft cheeses during pregnancy because listeriosis is particularly harmful to pregnant individuals, children, immunocompromised, and elderly individuals. So those populations in particular can become very, very ill and often die. With pregnant women, in fact, this disease often causes miscarriage or spontaneous abortion.

RACHEL FELTMAN: Getting back to how these pathogens get into unpasteurized milk, you mentioned that we can’t tell from looking at milk, from looking at the farm. And Dr. Gounder had alluded to very valid concerns people may have with a more industrialized food processing. So for people who are really focused on the fact that they’re getting this from a trusted farmer, it’s a local farm, and they really see benefits to that over buying a gallon of milk at a supermarket, what would you tell them about where the actual risks of contamination are?

NICOLE MARTIN: As we all know, dairy cows live on farms, right? These are agricultural locations. There is a variety of sources where bacteria can live and contaminate the animal or the milk itself. So we have soil and water and manure, obviously. Cows produce a lot of manure. They eat a lot of food. They produce a lot of manure.

Cows can also become infected with certain pathogens, right? So they can have sort of disease themselves from pathogens, but they can also have what we call subclinical disease. And that’s when an animal is infected and can shed that bacteria into the milk but it shows no signs of being ill. And that is where one of the big concerns come from, and people can say, oh, I choose raw milk, but I know this farm. I know these animals. They look healthy. They’re very clean. The farm is very clean.

All of that can be absolutely true, and I’ve been on those farms, but they can still contain the harmful bacteria that can make people ill. You just can’t use your senses to determine that.

RACHEL FELTMAN: Yeah and Dr. Gounder, back to you. I want to circle back to H5N1. I find it so interesting that this is getting people excited about raw milk since, as we know, bird flu has spread to cows, and there have been several cases of transmission to humans from farm workers. Does bird flu in raw milk pose a direct risk to humans that we know of?

CELINE GROUNDER: People who drink raw milk risk not only getting H5N1 bird flu infection but also E. coli, salmonella, campylobacter, and listeria bacterial infections. These bacteria are present in the feces of cattle. And when you think about the anatomy of a cow, the undersides of cattle are going to be highly contaminated with these bacteria. The udders of the cow are on the underside of the cow. So there is really no way to sterilely milk a cow and be sure that there is no bacteria entering the milk at that point.

E. coli, campylobacter, salmonella infections can cause fever, diarrhea, and abdominal pain, but they can also cause more severe disease, including bloody diarrhea, kidney failure, and other complications. Listeria, as Dr. Miller noted, can cause meningitis, and infection during pregnancy can be highly morbid and even fatal for the fetus or the newborn.

Now, does bird flu pose a direct threat to people at this stage? If you are infected with bird flu, yes, there is a concern. Historically, about half of people who have been infected with H5N1 bird flu– and this is around the world– half of those people have died.

So far in the United States, the cases have been pretty mild. We don’t entirely know why. The good news is that pasteurization kills the virus in the milk. The FDA and the USDA have done numerous tests now looking at different durations and temperatures of pasteurization, and that is effective in killing the virus in the milk.

But we’ve also done testing on pasteurized milk in grocery stores and other retail settings, and we are seeing fragments of dead virus. So, of course, it’s been killed by the pasteurization process, but we are seeing fragments of dead virus in that milk, which means it was there. The pasteurization worked. But if you’re drinking raw milk, you are certainly putting yourself at risk for infection.

RACHEL FELTMAN: Yeah. No, that makes a lot of sense. We talked a little bit about some of the supposed benefits, that there’s no evidence for, in raw milk. But folks also say it’s better for lactose intolerance or even just that it tastes better or it grants, some kind of strengthened immunity for children. Just to clarify, is there any evidence there, or is it really clear that the risks outweigh the benefits?

NICOLE MARTIN: Certainly from a scientific and data perspective, the risks absolutely outweigh the benefits, and we have plenty of studies that demonstrate that. And we know that in states where the sale of raw milk is legal that there is hugely higher risk of contracting illness related to raw-milk consumption. So the data is there. We have plenty of evidence that these risks are real and no evidence that the benefits are real.

But I do want to touch just briefly on something that you said. You said some people say that the flavor is better. That really can be the case based on personal perception, but it’s really driven by the fact that when you choose to consume milk from one farm, you’re getting all of the flavor profiles from that one farm, right? Typically raw milk has much higher fat level than pasteurized milk. When we pasteurize milk, often we standardize, which means we take the fat out and put it back in a standardized way. We don’t want one gallon of whole milk to have 3.2% fat and the next to have 4% fat. We want to have sort of a level playing field for everybody.

Typically when we pasteurize milk, when milk goes from various farms into the same processing facility, then they all get what we call comingled, right? They’re comingled together, and that kind of levels out some of those differences that you might see on a flavor perspective because all of that milk is going in the same tank.

And again, I’ll go back to this idea that you can get a pasteurized product that is a safe product from a single farm on farms that do that or for small processors. You can also get milk that’s not been homogenized, which is when we sort of break up the fat so that it doesn’t rise to the top. Some people like that cream rising to the top, and you get a certain flavor profile from that.

So again, I just want to come back to the idea that if that’s the value proposition for a consumer, that they like that unique flavor from a certain farm or they like the higher fat level, you can get all of those things in a pasteurized product and not have the risk of the foodborne disease.

Yeah, so perhaps for people who are already into raw milk or are curious about it, perhaps try a local trusted farm that you like the look of that also pasteurizes their dairy, and maybe your results will be even better.

And Dr. Gounder, there’s such an understandable instinct that people are reacting to. They want to make healthy choices for themselves and their family. So I do empathize with folks who are drawn to this kind of content on social media. What are some ways that people can make sure that the information they’re taking in is trustworthy?

CELINE GROUNDER: I think start by looking at what the source is. So legitimate media organizations, journalistic organizations have ethical standards of journalism, and they should have them posted on their site. So, for example, the New York Times has an ethical journalism handbook. So I would search whether there is such an ethical guideline for that particular publication. That tells you a lot about whether that’s a trustworthy source.

Secondly, who is actually providing the information or quoted as providing the information? Is it somebody who is an expert, a specialist in the relevant field? And I’ll give you an example where just having a credential is not necessarily being an expert in the field.

So we saw a lot of doctors, MDs during COVID who professed to be experts in COVID, but they were actually neurologists or radiologists, et cetera. So look and see whether the person has the appropriate, relevant expertise. So I think that’s two places to start to figure out if the advice/information you’re being given is something you can trust.

RACHEL FELTMAN: Yeah. No, that’s great advice.

I think that’s just about all the time we have for the hour. I’d like to thank my guests once again, Dr. Celine Gounder, editor at large for public health at KFF Health News and infectious-disease specialist and epidemiologist; and Dr. Nicole Martin, assistant research professor in dairy foods, microbiology, and food science at Cornell University. Thank you both so much for coming on the show this week. There was so much helpful information in there.

NICOLE MARTIN: Thanks so much.

CELINE GROUNDER: My pleasure.

Copyright © 2024 Science Friday Initiative. All rights reserved. Science Friday transcripts are produced on a tight deadline by 3Play Media. Fidelity to the original aired/published audio or video file might vary, and text might be updated or amended in the future. For the authoritative record of Science Friday’s programming, please visit the original aired/published recording. For terms of use and more information, visit our policies pages at http://www.sciencefriday.com/about/policies/