Ep 174 What’s the deal with raw milk: Part 1

Milkborne disease dropped from 25% to 1% of outbreaks after pasteurization

The hosts explain that in 1938, milkborne outbreaks accounted for 25% of all foodborne disease. By 2002, pasteurization had reduced that figure to about 1%, making it one of the greatest public health achievements.

"As cities grew, the dairy industry had to come up with solutions to meet the constant demand for milk. And the early decades of the industrial revolution this was maybe to keep small dairy herds housed either in open areas of cities or like just outside the city okay like 70 cows or so and then as the city populations grew these small herds grew to like 2,000 a head. Whoa. Yep. And then you're not going to find more area. Like you have to figure out how you're going to house all these. It's just increasingly cramped quarters. Right, right. Like too many cows in a small space. Yeah, exactly. Okay. And when these larger herds were still not sufficient to produce enough milk for a city. Milk began to be transported via rail. Keep in mind, refrigeration was not yet a thing. I was just going to ask, when did refrigeration become a thing? That I don't know. I can't believe I don't have this in here, but I don't know. Yeah. That's okay. But it wasn't a thing at this time. It wasn't a thing. Yeah. And so milk spoilage was a real concern, especially for the producers who introduced some nasty ways of dealing with it, right? Because like you're going to send a whole shipment of milk. You want people to actually buy it instead of having to throw it all away because it's spoiled. Right. Right. So maybe you add some formaldehyde. Maybe you do. Maybe you do. That actually did happen. That's a great plan. That is sarcasm. Yeah. Just in case. In case that doesn't come through. Yeah. Yeah. Milk formaldehyde and milk adulteration period was really a big problem. Okay. Yeah. So anyway, to bring it all together, by the mid 1800s, we've got no refrigeration, milk being transported long distances, harmful milk processing practices like embalming it with formaldehyde, cows housed in crowded and filthy conditions, humans basically living the same way in cities, and a lack of knowledge about how infectious disease spreads. Okay. Really great setup for people to get super sick. Yep. Sarcasm again. I have written a recipe for disaster. But it truly was a disaster. And I can demonstrate that with some numbers. So most European cities around this time had infant mortality rates of 150 to 300 per 1000 live000 live births. Oh, dear. In New York City in 1880, infant mortality reached 400 deaths per 1,000 live births. Oh, my goodness. Yeah. Compare that to today, the US, it's around 5.6 per 1,000 live births. Wow. It's just, it's so sad. World's different. Yeah. World's different. Yeah. Infant mortality, like you heard in our first 10 account, was a way of life. These high infant mortality rates were not solely attributable to milk, of course. There was a lot of things going on. If you listened to our last couple of episodes on childhood vaccines and the schedule, you'll know. Yeah. But milk did play a huge role and it was a lot huger of a role than I realized. Okay. Actually. Yeah. So for example, in Toronto in the early 1900s, spoiled milk was responsible for half of the 30,000 deaths in children. What? Yeah. Wow. Huge. Like, I think I've also seen estimates from one third to a half of infant mortality. Oh my goodness. Yeah. But like, what does spoiled mean, right? Like, how was milk causing so much illness and death? Yeah. Well, pathogens. It's the bottom line. Yeah. But cow's milk harbored pathogens. And so when that milk was not safely treated to prevent the growth of pathogens, people who drank this milk could get very, very sick. The sugars, fats, and protein in milk provides a substrate. It provides food for these pathogens to grow, right? You think about like a glass of water and it's why, I mean, of course, water is a huge route of transmission for many different pathogens. But milk, the pathogens can grow, grow, grow, grow, grow, grow, grow, where it's just everything. Milk is like a beautiful growing medium. Yes, it's like what you would want to culture bacteria. Exactly. Yeah. So it's not just like the ones that get put there, you know, from the milking process or from the storage process or from the handling process. It's like once they're there, they will just exponentially continue to grow because they love all the nutrients in milk as much as our bodies do. Exactly. Yeah. Yeah. And among the most vulnerable to these pathogens, of course, infants. Yeah. Babies. Why were infants drinking so much milk? I'm guessing we didn't have formula? Well, we did have some early formulas, but it comes back again to the Industrial Revolution. So women increasingly had to work in factories to help provide for their families, which meant that they would be gone for long, long stretches of time. They couldn't bring their babies with them and they couldn't breastfeed their infants. And so as a result, breastfeeding declined around 50 to 70% during this time. Oh, wow. Okay. Yeah. huge decline. And babies were instead fed like cow's milk alone or cow's milk supplemented with early formula. Or they were supplemented with cow's milk. But this cow's milk had not undergone any treatment for disease prevention. Right, right, right, right. So there was a 1905 epidemiological study of infant mortality between breastfed and cow's milk fed infant, and they found dramatic differences. In babies that were zero to three months old, infant mortality was 1.9% in breastfed babies and 92% in cow's milk fed babies. I mean, that makes sense too, just in terms of like nutritional differences in cow's milk versus human breast milk in a baby that young. Yeah. At one year old, just to carry this further, 6.2% of breastfed babies died compared to 36% of cow's milk only. Wow. Huge. I mean, these are huge differences. Babies fed cow's milk were 15 times more likely to die than breastfed babies alone. Wow. And again, you know, this was pre-modern day formula. Right. This is a very different time. Right. Very, very different time. But they didn't have other options. They didn't know as much about the nutritional differences. But it was like, this is all we've got. It's one or the other. Yeah. And of course, this was used to shame working women. Oh, of course. Or women who had no other option than to feed their baby cow's milk. It's always used to shame. Anyway. But these differences in infant mortality were not due solely to nutrition. Mostly they were due to pathogens. A number of different outbreaks were tied to milk. Typhoid fever, diphtheria, scarlet fever, septic sore throat, and of course, tuberculosis. Tuberculosis. Also diphtheria. What? I know. I know. But yes. Okay. Diphtheria. Awful. Yeah. So tuberculosis was a huge killer during this period, and it was greatly, greatly feared. In the late 1880s in the northeastern U.S., tuberculosis infected 20% of all cattle. Whoa! Yeah. And I'm assuming, they didn't mention this specifically, I'm assuming this is bovine tuberculosis. Yeah, probably. Which can still cause infections in humans. Yes, absolutely. And I know that you'll talk more about that probably next week. A little bit different. Okay. Okay. But anyway, from the same time period, late 1880s, 15% of all cans of milk were contaminated with the tuberculosis bacterium. No, thank you. Okay. But believe it or not, like those are some, those are some decent numbers. Like those are okay. Not bad, right? I mean, yeah. Well, yeah, I know. I know. Because in 1893, around 50% of the milk that was supplied to the city and county hospitals of San Francisco contained active tuberculosis bacteria. 50%. Why?"

History of milk as a disease vector in industrializing cities

Industrialization and urbanization created dangerous conditions for milk production, with larger herds and pooled supplies increasing pathogen transmission of tuberculosis, typhoid, and other diseases through dairy.

"Listen on the iHeartRadio app, but also goat, horse, camel, and so on. Humans started consuming milk probably around 8,000 to 10,000 years ago, And at some point, maybe around 8,000 or 9,000 years ago, a genetic mutation popped up in a subset of these humans that allowed them to keep digesting milk, specifically lactose in milk as adults. Lactose tolerance, lactose intolerance. You've heard about this before. And if you want even more details on the biology and the evolutionary history of this, check out our episode from all the way back in 2020. Wow. I know. Throwback. Also featuring one of my favorite firsthand accounts. Probably one of the best firsthand accounts of all time. Thank you so much, Katie. Truly. Yeah, truly. But the key thing to know about lactose tolerance, the ability to digest most dairy products, the ability to digest lactose, is that around one-third of the global population has this mutation and that it is not evenly distributed across the globe. Regions with the highest rates of lactose tolerance include Northern Europe, parts of North America, Australia, and certain parts of Africa. But what this means is that heading into the 19th century, milk was a diet staple in certain parts of the world where it was in high and constant demand. And it remained a staple even when people began moving from the country to the city, which posed a challenge to milk production and access. That makes sense. Yes. Before the Industrial Revolution, which is the period that we're now entering in the story, milk didn't travel long distances, kind of like in our firsthand account, right? You could mostly just get it from a local farm, which of course, I feel like I need to say, did not mean that the milk was completely safe or free of pathogens or just did not spoil at all. It was just perfect pure milk, right? Like, no. It just was like, that's where you got it. That's where you got it. Yeah. But with the growth of cities, these problems of spoilage and freshness intensified. Right. Of course. In his 1771 novel, The Expedition of Humphrey Clinker, which, by the way, has a 3.4 on Goodreads. And I don't know why i find that so funny but it is that because it's like from the late 1800s or sorry the late the late 1700s oh is that like a high rating though or i don't know but it's just i think the concept of rating a book from 250 years ago and being like loved it i't know. I liked it. It was fine. Two stars. And it's just like an account of his expedition too? Oh, no. Sorry. I'll keep talking. It's a novel. And from this novel, there's a passage where the author, Tobias Smollett, paints a lovely picture of the journey that a pail of milk might take from cow to cup."

Lactose tolerance is a genetic mutation in about one-third of humans

About one-third of the global population carries a genetic mutation allowing continued lactose digestion into adulthood, concentrated in Northern Europe, parts of North America, Australia, and certain African regions.

"Listen on the iHeartRadio app, but also goat, horse, camel, and so on. Humans started consuming milk probably around 8,000 to 10,000 years ago, And at some point, maybe around 8,000 or 9,000 years ago, a genetic mutation popped up in a subset of these humans that allowed them to keep digesting milk, specifically lactose in milk as adults. Lactose tolerance, lactose intolerance. You've heard about this before. And if you want even more details on the biology and the evolutionary history of this, check out our episode from all the way back in 2020. Wow. I know. Throwback. Also featuring one of my favorite firsthand accounts. Probably one of the best firsthand accounts of all time. Thank you so much, Katie. Truly. Yeah, truly. But the key thing to know about lactose tolerance, the ability to digest most dairy products, the ability to digest lactose, is that around one-third of the global population has this mutation and that it is not evenly distributed across the globe. Regions with the highest rates of lactose tolerance include Northern Europe, parts of North America, Australia, and certain parts of Africa. But what this means is that heading into the 19th century, milk was a diet staple in certain parts of the world where it was in high and constant demand. And it remained a staple even when people began moving from the country to the city, which posed a challenge to milk production and access. That makes sense. Yes. Before the Industrial Revolution, which is the period that we're now entering in the story, milk didn't travel long distances, kind of like in our firsthand account, right? You could mostly just get it from a local farm, which of course, I feel like I need to say, did not mean that the milk was completely safe or free of pathogens or just did not spoil at all. It was just perfect pure milk, right? Like, no. It just was like, that's where you got it. That's where you got it. Yeah. But with the growth of cities, these problems of spoilage and freshness intensified. Right. Of course. In his 1771 novel, The Expedition of Humphrey Clinker, which, by the way, has a 3.4 on Goodreads. And I don't know why i find that so funny but it is that because it's like from the late 1800s or sorry the late the late 1700s oh is that like a high rating though or i don't know but it's just i think the concept of rating a book from 250 years ago and being like loved it i't know. I liked it. It was fine. Two stars. And it's just like an account of his expedition too? Oh, no. Sorry. I'll keep talking. It's a novel. And from this novel, there's a passage where the author, Tobias Smollett, paints a lovely picture of the journey that a pail of milk might take from cow to cup."