This Podcast Will Kill You - Ep 46 Lactose Intolerance: Never trust a fart

Episode Date: March 17, 2020

Everyone loves a good poop story, don’t they? We certainly hope so, because our good friend Katie shares a fantastic one to kick off our episode on lactose intolerance. In this episode, we explore what lactose is and the symptoms that lactose non-digesters experience when they eat some sneaky cheese or ice cream. Then we explain that this episode is actually flipped - turns out that not being able to digest lactose is the normal state, and those of us who can are actually the mutants! We trace the origins of this mutant allele and how the persistence of pastoralism spread milk drinking far and wide. Where do we stand with lactose intolerance today? Tune in for that answer and for an abundance of milk facts to arm yourself with for the next pub trivia night. See omnystudio.com/listener for privacy information.

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Val, bad pun. Outdo it with Intuit QuickBooks. Feature availability varies by product. Hi, everybody. My name is Catherine Sampson, and I met both of the errands in graduate school at the University of Illinois. I'm currently an AP biology teacher down in Texas

where I'm from. They asked me to share my story about my lactose intolerance. throughout my life, and of course, I jumped at the opportunity to be on the podcast and share my poop stories with basically the entire universe. There was one part of my life that I think was one of the most formative defecation experiences I've ever had. And it goes a little something like this. My mom and I, hi, mom, we were sitting in a restaurant eating lunch one day, and I just ordered something off the menu that appealed to me. And maybe about 30 minutes later when my mom and I were shopping at the store that is very famous for selling containers of all varieties, we were walking

down the gift wrapping aisle and I felt something kind of odd in my bowels. And so I thought to myself, that's not normal, but it'll be okay. Just shake it off. Just keep it. walking everything's going to be fine and I remember thinking back about this moment and I went maybe that's why they called it a bowel movement you know because I physically felt my bowels moving inside my body so you know I continue walking and I start feeling like a buildup of gas inside my body and so for all of the people out there have ever felt that you know what I'm talking about. And so you think for a moment, well, maybe if I let it out and I relieve that pressure

inside my body that everything will be okay. But for me in that moment, if I can give y'all one piece of advice is to never really trust a fart. I unfortunately did trust this fart and it ended up being very bad for both me and my pants. So I ended up defecating myself in the middle of the gift wrapping aisle in some light blue jeans, very light blue jeans. And I remember walking up to my mom going, I think I just poop my pants. And I remember for the rest of my life, she looked at me and laughed and went, what? And I said, no, mom really, I just, I put my pants. And she looks at me and she goes, well, I'm not done shopping. Nothing is going to change it right now, right? Katie. And I said, okay, yeah. And so from that moment on, I realized that, you know, I'm standing in the middle of

public in Houston, Texas, and I just put my pants and this was going to be my life. And so I should probably make some concerted decisions to recognize what I'm eating and tell people that I'm lactose intolerant. And so I started doing that, you know, that was when I was 19, so nine years ago. But nowadays, when I go to restaurants, I don't really get taken seriously a lot saying that I'm lactose intolerant by the waiters or something like that. So I usually just say I'm allergic to milk, I'm allergic to cheese, or if it's a hard day, I just tell them I'm vegan and I go with it. So yeah, that's just, that's my poop story. And I hope that everybody out there can maybe relate to that a little bit and recognize that we shouldn't be ashamed of maybe pooping her pants in public. That was, that's, that's my

story y'all that was amazing as always as always thank you so much katie for your always always enjoyable stories the best the best not only poop stories but definitely the best poop stories without a doubt hi i'm erin welsh and i'm aaron oman updike and this is this podcast will kill you and today we're talking about lactose intolerance or lactase persistence because really that's the there's so many names for this I love it oh my gosh I think we're going to have to do some sort of like a primer or briefing on the on the names a lot of the articles that I read had like tables of all of the acronyms that they use because there's so many different ways to talk about I wish that the the articles I looked at had tables because that would have made my life a lot easier I was like oh no does this one stand for again So to get us through this episode, what are we drinking? Our quarantini of the day is truth or dairy.

And appropriately, it is essentially a milk punch. So it's got milk and rum and brandy or cognac and nutmeg. Listen, do you say milk or milk? I say milk. Because I got made fun of this morning for saying, Milk. For saying what? I guess I say it weird.

Milk. Oh, great. So it's going to be... It's going to be another one of those episodes where Aaron can't pronounce the thing we're talking about. It's fine. I'll just say dairy. There we go. We will post the recipe for the quarantini and the non-acolic placeboerita on our website.

This podcast will kill you.com and all of our social media. pages, so check it out. Yes, most definitely. Do we have any other business? No, I don't think so. Let's just get started. Okay. We'll take a quick break first. Dinner shows up every night, whether you're prepared for it or not. And with Blue Apron, you won't need to panic order takeout again. Blue Apron meals are designed by chefs and arrive with pre-portioned ingredients so there's no meal planning and no extra grocery trip. There, assemble and bake meals take about five minutes of hands. on prep. Just spread the pre-chopped ingredients on a sheet pan, put it in the oven, and that's it. And if there's truly no time to cook, dish by Blue Apron meals are fully prepared. Just heat them in

the oven or microwave, and dinner is ready. And here's the exciting news. Blue Apron no longer requires a subscription. You can order meals when you want them and skip when you don't without adding another recurring charge. Order now at blueapron.com. Get 50% off your first two orders plus free shipping with code this podcast 50. Terms and conditions apply. Visit blue apron.com slash terms for more information. Anyone who works long hours knows the routine. Wash, sanitize, repeat. By the end of the day, your hands feel like they've been through something. That's why O'Keefe's working hands hand cream is such a relief. It's a concentrated hand cream that is specifically designed to relieve extremely dry, cracked hands caused by constant hand washing

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I'm very excited about this episode. This is our first, the first non-crossover, non-disease episode. Wait a second. Like, we've had crossover episodes where we talk about poisons or things that will kill you. I see what you mean. But this is our first just me and you, and we're talking about maybe not even a disease. Well, it's not really. It's not.

It's really not. Spoilers. So I figured that because this is a wonky episode where we aren't talking about a disease, I would do the biology section in a bit of a wonky way. Okay? Perfect. Okay. So we're going to start off the biology section where we usually end up, and that is with the symptoms, because we usually kind of end with that. So if we're being honest, we pretty much already know the symptoms of lactose intolerance, a.k.a. lactose malabsorption, aka lactase non-persistence, aka hypolactasia. It's another term for it. I've seen all of these. This is good. Nice refresher.

So we know these symptoms. Aaron, what are the kinds of symptoms? Bloading, rumbly tummy, diarrhea, farts. Do you want to know the fancy word for grumbly tummy? I do. Borberigmi. Can I get the etymology of that, please? Let me Google that for you. It's Greek.

Great. It comes from the Greek borbarygmos. Meaning what? Meaning a rumbling or gurgling noise made by your tummy. Wow, so it really is specifically like that. The word has one purpose. Amazing. I know.

Oh, Borberigmus. Yeah, that's a big one. That's the medical term for a gurgly tum. Abdominal pain, I think you said. Farting. Diarrity. Diarrhea tends to be less common in adults, at least according to the literature. But we'll kind of talk about why you might see diarrhea even if you're an adult.

Does that make sense? All right, cool. So we all know what we're dealing with here. But to talk about lactose intolerance or lactose malabsorption, we have to actually take a step back and first talk about one of our favorite things, the gastrointestinal tract. Yeah. So your guts, because lactose malabsorption is a gut problem,

we're going to talk about how it functions normally in order to understand. what goes wonky in these situations. But hold on. Okay. Lactose malabsorption is the normal state. Okay. Yeah, this is going to get confusing. Yeah.

Yes. I mean, yes and no, right? Like, mammals can digest lactose for at least a portion of their lives. Yeah. Yeah. So as adults, some mammals, most mammals, can no longer. digest lactose. But let's talk about how your GI tract normally would handle lactose if it's able to digest it. Okay. Okay. And just kind of how your GI tract handles sugars to begin with.

Okay. We're going back to the very beginning here. Okay. Okay. So the main function of your GI tract is what? To digest food? Mm-hmm. Yeah, exactly. Absorb nutrients. Perfect. waste. You know it all. Okay. So your gut has three main divisions, right? You have like your four gut, that's your mouth and maybe down to your stomach, right? Then you have your mid gut. That's your small intestine and then your hind gut, which is like your colon and your butt. Okay. Okay. So digestion, which is that main function of your gut, starts at the very top in your mouth where you chew things and you physically and chemically start to break them down. And then it travels down to your stomach where that digestion process continues, like physically your stomach clenches in and out,

plus you've got all that acid in there, right? Then as your food moves into the small intestine, your small intestine has two main goals. Finishing up that digestive process and this one's important, absorbing all those nutrients that you unlocked during that digestion process. Okay. So to do that, your small intestine has a bunch of different enzymes, which are responsible for breaking down all these nutrients into the smallest possible particles so that they can pass through the intestine wall and make it into our bloodstream. Okay.

So some of these enzymes come from the pancreas, and some of them come from cells in the wall of the intestines themselves. But these enzymes are all really important because your intestine basically acts as a filter, and large particles can't make it through your intestine wall into your bloodstream. So everything has to be broken down into really small molecules. In the case of sugars, it has to be broken down into. to monosaccharides. That means one piece of sugar. Cool. Cool. Okay. So anything that can't be digested or can't be broken down small enough will stay in your small intestine and keep traveling down to your colon. Your colon is the last part of your GI tract and it's basically

responsible for sucking all the water out of the junk that's left in there so that you don't lose too much water. Oh, aka. diarrhea, aka diarrhea. And then you have a whole bunch of bacteria in your colon, which help break down any last particles that might have nutrients in there that you want so that you can absorb absolutely everything possible. And then what's left is poop, and you poop it out. Excellent. So that's your GI tract in a nutshell. So what happens in lactose malabsorption or lactose intolerance? So lactose is a sugar. It's a disaccharide. So that means two sugars bound together. It's galactose and glucose, if you care about that sort of thing. Oh, I mean, I didn't think I did and I don't think that I do. But still interesting. But you're good to know. Yeah. Okay. And lactose is found in milk, of course, milk, dairy products of all kinds. I don't hear you. I don't hear milk and milk, but. Thank you. I appreciate that because I really got made fun of.

And so since lactose is a disaccharide, we know that it has to be broken down into monosaccharides, the two that it's made up of galactose and glucose, in order to be absorbed by the small intestine. It turns out that this happens in our small intestine by a specific enzyme called lactase. So what happens right off the bat is that if lactase isn't able to break down lactose into its two component parts, then you will have undigested lactose, a dysachcharide, that's left in your small intestines

to travel down to the colon. Okay? That's the main thing that happens in lactose intolerance or lactose malabsorption. So, the function of the colon is to absorb the water that's left and leave your poop behind.

When you have undigested sugars like lactosephorption, like lactose, they serve as a really great food source for bacteria. So the bacteria in your colon gets super stoked. And they will go nuts eating this sugar, this lactose, and they convert this sugar via biochem we're not going to get into into fatty acids and hydrogen gas. Aha. So guess what it feels like when your intestinal bacteria start producing a bunch of gas? I mean, whatever the Greek word you said. Borberigmi. Borberigmi.

Exactly. You're literally going to have a bunch of gas in your colon. Okay? And that is why you have these symptoms if you have a bunch of lactose that makes it all the way from your small intestine down into your colon. Now, the other thing that can happen if you have undigested disaccharides like lactose in your colon is that it turns out that this sugar, this disaccharide, it's what we call osmotically active, which means that it's going to draw water towards it. So if you have sugar left in the lumen of your gut, you're not going to be able to absorb water through the walls of your colon, rather water is going to stay in your colon, because in your body there has to be a balance between the solutes and water.

Right. Okay. So what does that mean, Erin? If you've got a bunch of water left in your colon. I think we both know where this is going. It's to the bathroom for some loose stool. Exactly. Diarrhea.

As a fun side note, this is how osmotic laxatives work. So if you've ever taken Miralax or... lactulose, lots of kids take it because kids are always constipated. That's exactly how they work. It's basically just big molecules that can't be broken down by our enzymes or our gut bacteria. So then it draws a bunch of water into your colon. Wow, that sounds uncomfortable. Yeah, I mean, it just cleans you out. It's what you use if you're having a colonoscopy. Yeah. Okay. So, that That is how lactose intolerance or lactose malabsorption happens, why it causes the symptoms that it causes.

So now we have to get back to the beginning where we mentioned this isn't really a disease state. So why is it that some people have this and some people don't? Well, turns out there's a few different ways. Let's talk about the least common first. Okay. First, you could be born with very low levels of this lactase enzyme function. That is called congenital lactase deficiency. You can imagine that because mammals' main food source is breast milk, which has lactose, that would be pretty bad.

So this is pretty rare. Okay. How rare? Good question, actually. I never did find it. I have star star epine. and I never found good epi numbers on this. It's most common in the Finnish population.

Really? Yeah. I know. You know, okay, this is jumping the gun a little bit. Okay. But in northern European countries and northern European populations, lactase persistence, so the ability to digest lactose is pretty high across the board. Yes.

But when I was living in Finland, I saw it so. many like lactose-free or low-lactose milks and yogurts and blah-blah-blah-blah. We'll talk about it. Okay, great. Yeah. I was like, wait a second, but I thought, yeah, okay. So yeah, this congenital lactase deficiency, you can imagine you would recognize this pretty early on when a baby is an infant because they would have some pretty severe symptoms

from breast milk. This is an autosomal recessive disorder. So this is a genetic disorder. Okay. But again, it's pretty rare. I don't have exact numbers. But that's one way that you could end up with lactose malabsorption. Another way is if you are a very premature baby, sometimes premature babies have what's called developmental lactase deficiency because their GI tract just isn't quite developed enough. And it, for some reason, turns out that lactase is one of the last genes to get properly turned on during development. But this is something that would be rather transient. Okay. Interesting that it's one of the last genes. I know.

You'd think it'd be an important one. But also, like, so is surfactant production, and that's, like, essential for life. That's what allows your lungs to stay open. Oh, that's pretty crucial, I think. Yeah. It doesn't happen until, like, after 35 weeks of gestation. Anyways. Huh.

Another way that you could end up with being not able to. you absorb lactose very well, is if you get a GI-tracked infection, for example, Giardia. Wow. Okay. That kind of GI-track infection can cause damage to your small intestine where this enzyme is located so that even after clearance of that infection, you don't have proper function of that lactase enzyme. So it basically just causes damage to the cells of your.

small intestine. Okay. So in theory, you could still produce lactase, but the cells are so damaged that there's no way to produce lactase. Okay. Precisely. But finally, number four, the most common way that you can have lactose malabsorption is... I feel like people are going to get angry with us, because we're describing the normal state of things. Well, then let me say this, Aaron. The fourth option is you can be a normal human adult, okay? Okay. In most humans, in fact, in most adult mammals, it is totally normal for the activity of the lactase enzyme to downregulate as we age.

What does that mean? It means that this enzyme works really well when we're babies and infants, and literally by the time we're like six years old, the action of this enzyme is substantially less than it was when we were babies. Right. So, lactase persistence, which means that your lactase enzyme is on at high levels throughout your life, is actually the mutant state. And that is what is present in some populations. And Aaron, I'm pretty sure you're going to talk about why and where this mutation came from.

Definitely. Awesome. But yeah, the bottom line is, if you can drink milk as an adult human and not have borberian, and tons of gas and abdominal cramping and possibly diarrhea, you're the mutant. We're the mutants. So I think that's really fun. So I don't know. This episode is lactose intolerance, but it's really like weird lactase persistence.

Yeah. Maybe we'll just milk mutants. Milk, milk mutants. Milk mutants. But, Erin, what you mentioned about in Finland having really high levels of seeing a lot of like lactate type products on the market. Low lactose products. It turns out that people are actually really bad at knowing if their symptoms are associated with lactose intolerance or not. Right.

So when they've done studies to look at like what your tolerance levels actually are, it turns out. out that even people with lactose intolerance or lactase non-persistance can actually tolerate about a cup or a little more than a cup, like 12 ounces of milk a day. I was going to make that point or like bring that up that lactose intolerance and lactase non-persistance are different things. Like you can also have different levels of lactose intolerance. Exactly. Even if you don't produce lactase into adulthood. Exactly, because lactose intolerance is essentially you having symptoms from after you drink milk.

But because your colon bacteria can actually digest lactose, as long as you're not drinking or eating so much lactose that you become symptomatic, then it's no problem, right? So the only problem is if you have so much that basically you're whatever, whatever your individual colon bacteria can handle after that point is when you're going to become symptomatic. So for some people, that might be like one piece of cheese. And for other people, even if their lactase enzyme is very low activity or no activity, they might still be able to drink like a full glass of milk and not have any problems. So the microbiome, the gut microbiome and lactose, Yes. The bacterial species that feed on the lactose, like, is there, have there been any studies that look at maybe like different amounts of that type of bacteria or anything like that in association with symptoms or tolerance or whatever else?

Like whether you could give somebody probiotics and lessen their symptoms? Yeah. Yeah, there have been studies of it. To my knowledge, they're not like, we don't have a pill, a probiotic pill that you can take to be able to digest. lactose with no problem at this point, but there are definitely people looking into it because for sure differences in colon bacteria would lead to differences in symptoms. And there have been a number of studies that have shown that if you kind of train your colon bacteria over time, then you might actually be able to tolerate greater levels of lactose. Although other studies have said maybe that's just a placebo effect. So, in any case, if you don't have the allele that allows you to produce lactase, you're not digesting.

On your own, you're not digesting it. Yeah. So tell me about lactate and the little pills, the little helper pills. What do those do? So the lactate pills that you take are lactase enzyme. Oh, okay. So that's literally just going to break down the lactose before it makes it to your colon. Okay. There are other things that you can put like in your milk, like droppers. I don't know if it's a liquid or But that is yeast or bacteria that you can let sit in your milk and it'll digest the lactose for you. I think I am hearing milk. I can't help it. I mean, you do you.

There's that whole like what part of the country dialect test are you from? I wonder what, isn't milk a Midwest Midwestern thing? I don't know. Brett and I are from the same place and he makes fun of me. So. I mean, maybe you've picked it up since living. living in Illinois. Who knows? Milk. Milk. I just don't hear a difference, quite honestly. This episode is just going to be 45 minutes of us saying milk. Milk.

Anyways, Erin, that's it. That's all I got. That's the biology. Wow. Okay. Very interesting. That was also some of the epies, so. Are you ready to hear about the history of lactase persistence? That's what I'm here for. Okay, excellent. Let's take a quick break. Anyone who works long hours knows the routine. Wash, sanitize, repeat. By the end of the day, your hands feel like they've been through something. That's why O'Keeffe's Working Hands hand cream is such a relief.

It's a concentrated hand cream that is specifically designed to relieve extremely dry, cracked hands caused by constant hand washing and harsh conditions. Working hands creates a protective layer on the skin that locks in moisture. It's non-greasy, unscented, and, absorbs quickly. A little goes a long way. Moisturization that lasts up to 48 hours. It's made for people whose hands take a beating at work, from health care and food service to salon, lab, and caregiving environments. It's been relied on for decades by people who wash their hands constantly or work in harsh conditions because it actually works. O'Keefs is my hand cream of choice in these dry Colorado

winters when it feels like my skin is always on the verge of cracking. It keeps them soft and smooth, matter how harsh it is outside. We're offering our listeners 15% off their first order of O'Keefs. Just visit o'keefscompan.com slash this podcast and code this podcast at checkout. This is Bethany Frankel from Just Be with Bethany Frankel. Listen, I have a bone to pick with these dog food brands calling themselves fresh, natural, healthy. Sounds great, but a lot of these quote-unquote fresh dog foods in your fridge are not even 100% human grade, which is why Feed your babies. Just Food for dogs. It's good enough for big and smalls. My precious babies. So it's good enough for your babies. 100% human grade, real ingredients, beef, sweet potatoes, green beans, delicious. These are foods that you would want to eat.

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Listen on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right. So I want to start off by talking a bit about milk and then about lactase persistence. And so for this part, just to clear things up, because most of the time, when I'm talking about the history of lactose intolerance or lactase persistence, I'm talking about the specific allele and not necessarily the disease itself. And so I'll say lactase persistence, and that refers to people who have the allele that allows them to digest lactase throughout, or lactose throughout their lifetimes. Right. Okay. Milk is a pretty revered liquid. If the myths and folklore surrounding it are any indication, the Greek word for milk is gala, which forms the basis of

the word galaxy, and ours is called the Milky Way. So yeah, isn't that cool? Because according to Greek mythology, yes, the Milky Way was formed when Hera spilled milk. while breastfeeding Heracles, aka Hercules, with each drop of milk forming a star. Huh. Yeah. And the ancient Greeks weren't the only ones to have creation myths with milk playing a central role.

So, for example, in the Falani people of West Africa, there's a myth that the entire world began from one huge drop of milk. And in Norse mythology, a frost ogre named Imir was kept alive by the milk of a cow made from thawing frost. Wait, wait, wait. The cow was thawing... The cow was made from thawing frost? The cow was made from thawing frost.

And then the milk made... The milk from that cow of thawing frost. Okay. Weird. That's my understanding. And milk was believed to be a type of blood for a really long time. And so that also, as we have talked about in the hepatitis episode also carried a bunch of weight. And it was used as the blood of Christ for a long period in the Catholic Church until being replaced by wine. I got to tell you that my brain

can't keep flipping between like cow milk and human breast milk. And it's grossing me out both ways either time. Well, so. Yeah. And that's the thing is that like milk holds a lot of meaning for many human cultures, and a lot of that is human breast milk. But with some of these, as with the cow made from thawing frost, it also shows that animal milk had significance as well. Right. Okay, so let's see. A refrigerator was built in the U.S. in 1803, like the first time, for the purpose of keeping

butter. Butter. Butter. The CIA once tried to poison Castro by slipping like a pole. poison pill and his ice cream. He was a huge fan of ice cream, apparently. Who isn't? Pints. There was a lot of power in milk. So in breast milk, it was believed often that picking a wet nurse with the right temperament was incredibly important in the baby's personality. And also goat's milk or sheep's milk or cow's milk was seen as nourishment and was also used as a sacrifice as well.

And milk wasn't universally hailed as a wonder liquid, though. So for instance, for millennia, fresh milk could pretty much only be consumed on farms. And so it was held in low status as like a peasant beverage. Oh, interesting. Yeah. And this created cultural tensions or conflicts. So in southern Europe, the Romans looked down upon those in northern Europe who drank more fresh milk because it was colder there and the milk kept better. and in addition to making people more, quote, barbaric, milk was also thought to be bad for you health-wise.

Huh, interesting. And fresh milk wasn't the only thing that got labeled with this, like, as a suspect food. Cheese and other dairy products also got the stamp. But as you mentioned, milk is crucial for humans in infancy, just as it is for all mammal species. And here comes like, this is just going to be an influx of trivia. Not all mammal milk is created equally. Yes. Some are loads fattier than others, like Northern Seals at 53.2% fat.

Oh my. Humans, for reference, 4.5%. Whoa. I mean, and you know that one of my favorite bits of trivia is that the breast milk of some whales has the consistency of toothpaste. Toothpaste. I love that image. I think that in my fridge, like, we have a lot of milk in our fridge right now, and you can see the fat as it rises to the top when it gets cold, you know? And knowing that that's only 4%, imagine, imagine seal milk in your fridge.

53.2%. Yeah. Imagine that butter. Oh, man. I mean, just toothpaste, consistency, best milk. I mean, it makes a lot of sense because if you're in the water, you would have. I didn't want it to just immediately diffuse or whatever. Yeah. So get diluted. You wouldn't want that.

You want that toothpaste milk. Did you know also that some pinopeds, like sea lions and walruses, lactose isn't present? Really? Yeah. So what's their main carb? I don't know. I didn't. You look it up?

No, it's okay. I saw it. It's like, I was like, oh, cool. Bit of information. That's it. not reading any further. But humans are the only mammal that consume the milk of other species and continue to do so throughout their lives. And in retrospect, it's kind of easy to see why this practice would have been popular.

Milk of various ruminants like cows and reindeer could be used to make yogurts or butters or cheeses that would keep for a decent period of time. And that could be especially important when other food was scarce. Side note, did you know that unsalted butter was a recent invention because basically refrigeration was the only way to keep unsalted butter fresh? That makes so much sense because salt is a preservative, so you would have to have salted. I hope that you go to Trivia Night, you and anyone who is listening, you get asked a question about milk that this episode will give you. The question is going to be what carbohydrate do Pinnipets have? Uh-huh, instead of lactose. Well, sorry, guys.

There's only so much I can do. Okay, but of course, the majority of humans can't actually digest lactose into adulthood. And this feature, this whatever, this pattern has been recognized for millennia. Hippocrates in the 5th century BCE said, quote, cheese does not harm all people alike. And there are some people who can eat as much of it as they like without the slightest adverse effects. Indeed, it is a wonderfully nourishing food for the people with whom it agrees, but others suffered dreadfully.

As you heard, in Katie's pertain to count. Katie can attest. And Galen, who lived in the second century CE, observed and described lactose intolerance, and there were many ancient writings that advised against the consumption of milk after weaning. So why can some of us digest lactose, apocrym. approximately 35% of us. Okay, so first to answer that, let's look at the global pattern of lactase persistence to see if that gives us any clues. So these are the proportion of people who can continue to digest lactose into adulthood.

In Eastern Europe, the frequency of lactase persistence is between 15 and 54%, whereas in the British Isles in Scandinavia, that ranges from 89 to 96%. Whoa! Yeah. That's even higher than I thought. And in northern India, around 63% of people have lactase persistence compared to 23% in the south or the east. Erin, that makes so much sense for something that I was reading where I went, that's weird. And in some pastoralist populations in Sudan, lactose persistence is around 64%.

But in a nearby non-pastoralist group, that number is around 20%. So there's a common thread here, and that thread is that lactose persistence might have something to do with pastoralism or dairy farming as a way of life. So what came first? Milking or lactase persistence. Ooh. So one hypothesis, which is kind of like a chicken and egg scenario, is whether pastoralism only developed in those populations where lactase persistence was already high. This is called the reverse cause hypothesis. Uh-huh.

And this view kind of says that lactase persistence wasn't selected for necessarily, and the explanation for variation in rates is just random through, like, genetic drift. Huh. But another hypothesis, and this one is the one that has more support, is the culture historical hypothesis, which states that lactose persistence emerged and was selected for after pastoralism was adopted, meaning that being able to digest lactose into adulthood made you more likely to survive and reproduce. And one piece of support for this is that archaeologists have found organic residue and pottery from around 6,500 BCE in Western Turkey,

where lactase persistence is low today. And so this suggests that animals were milked before lactase persistence arose. So when did milking begin? Then. Milky animals probably began in the Middle East, possibly Iraq or Iran, around 8 to 10,000 years ago. So like Neolithic Revolution times. Yeah. It's a long time. A long time. But also not that long for the, like in terms of thinking about human evolution, which is, so there was a long held belief or viewpoint that humans had basically stopped evolving 50,000 years ago. But of course we know that that's not the case now, especially as like genomic technology has really shown that like evolution is happening on many different time scales. And anyway, lactase persistence is a great example of how humans have continued to evolve. Yeah, especially considering how widespread that allele now is in some populations, that it was that relatively recent. Yeah.

Okay. So there's a depiction of people milking cows on the wall of a temple dating back 5,000 years in ancient Sumeria, but milking probably began long before that and cows weren't the first. Goats and sheep were actually the first livestock to be domesticated around 11,000 years ago, followed by pigs and cattle around 500 years after that. Huh, I didn't know that. So people may have first tried milking goats or sheep or may have first tried milking goats or sheep or maybe even a camel. So the Bedouins, for instance, relied heavily on camel milk for their survival.

Bedouin means desert dwellers. Also, Bedouin is a really amazing musical artist. Her tiny dust concert is incredible. And Bedouins were traditionally nomadic. And many still are, but that traditional way of life has declined. But while on the move, camels played a major role in every aspect of life, shelter, transport, warmth, and of course, food production. And the milk produced by a camel is pretty incredible. Camels themselves are pretty incredible. Camels feed on the spiky salt bush, which gives their milk a salty taste. At times of food scarcity, camels will dilute their milk to make it last longer.

And in times of plenty, that milk can be incredibly fatty and rich in protein. Huh. So, yeah. More milk facts for you. I read a book literally titled milk, so. Also, I looked it up and pinopeds and cetaceans just have the lowest amount of carbohydrates. Oh, that's why they don't have lactose. Okay.

Yeah. Cool. Go fig. Go fig. So at some point, after the advent of agriculture and domestication of livestock, a mutation emerged that allowed humans to continue to produce lactase into adulthood. So this is probably around 8,000 or 9,000 years ago in Central Europe. There are different models that kind of show a variation of ranges from like 6,000 to 10,000 years ago,

but that seems to be like the central accepted range. Okay. And clearly this mutation had some benefits because it spread rapidly and widely throughout Europe in parts of Africa as well, reaching frequencies, as I said, of over 95% in some places. And so why would being able to consume lactose as an adult be advantageous? And there seemed to be three main hypotheses for why continued milk consumption could be selected for. And the first is that in pastoralist societies, so ones that keep cattle for milking and meat consumption, drinking milk would have meant more nutrition.

If milk is a constant part of your diet, but you have diarrhea and horrible stomach pains whenever you drink milk, it's easy to see how your health could be negatively impacted and that people who had the ability to digest lactose into adulthood might have slightly higher fitness if you're relying that heavily on milk. Another hypothesis is that drinking fresh milk could have been super beneficial to people in high latitudes like in northern Europe where lactase persistence is high because it would have allowed them to get vitamin D during the long winter months and that would have prevented things like rickets and also helped calcium absorption.

And it's true that you see more lactase persistence and fresh milk consumption in northern Europe compared to the Mediterranean where lactase persistence is lower and cheese tends to be the main dairy product consumed and cheese can have less lactose in it, depending on how it is prepared. A lot. Yeah. And finally, another hypothesis about the evolutionary benefits of fresh milk is that for people living in arid environments, milk would have been a source of water. And if you had diarrhea every time you drank your only liquid source, you would be super dehydrated.

Yeah. Not good. Not good. And we do see that in pastoralist groups in the hot arid parts of the world, lactase persistence is pretty high. But it doesn't seem to be as cut and dry as lactase persistence evolving alongside the cultural tradition of drinking milk. Because as we've talked about, milk or dairy products are regularly consumed in groups that have low lactase persistence.

But as we said, lactase non-persistence and lactose intolerance are different things. So you can kind of up your tolerance, but you'll never be able to digest lactose. Right. Okay. So anyway, one paper I looked at tested these different hypotheses to see whether any of them are supported by patterns of where lactose persistence is high or low. And what they found was that the vitamin D hypothesis and the dehydration hypothesis weren't supported really?

I'll also say that milk is actually a cruddy source of vitamin D. We add vitamin D to milk. Does that have anything to do with pasteurization? No, I don't believe so. I don't believe so. Okay. Yeah, I mean, even like human breast milk is a crappy source of vitamin D because we make it ourselves if you're in the sun.

Well, but I think their point was that if you're in Northern Europe, there literally is no sun. Right. So maybe any vitamin D would be better than none. Yeah. Yeah. I mean, it's not a very good source of vitamin D. Well, regardless, it's not.

It doesn't seem to be supported. Makes sense. But they did find that the lactase persistence evolved in people who kept livestock. So that seemed to be the best supported hypothesis. Okay. So basically, pastoralism led to the spread of the mutation that allowed for lacktaseaseasease. lactose digestion into adulthood. Makes sense. And we probably see different rates of lactase persistence geographically because selective pressures for lactase persistence may have been

different in different regions, which makes sense. So if you didn't rely heavily on milk, for instance, then that selection pressure wouldn't be there. And the pressures probably weren't constantly applied. So like lactose persistence may have only been selected for during extreme circumstances, like during a famine. But regardless, it does seem that being able to digest dairy products into adulthood was beneficial. And a couple of papers I read argued that lactase persistence and the reliance on a dairy economy led to the widespread expansion of a group called the Proto-Indo-Europeans.

I have not heard of that. This is an important group linguistically, apparently. So I learned. I hope I don't really butcher this whole explanation. but the proto-Indo-Europeans were a group of people whose existence is mostly inferred from linguistics rather than from like physical evidence. Okay. And they existed around the late Neolithic, so like five or six thousand years ago,

and were among the first to domesticate the horse. And so from somewhere probably in Eastern Europe, they spread across Europe, Western Asia, and the Indian subcontinent. And wherever they spread, their culture did as well. Dairy farming grew particularly in places where it was favored, such as Northern Europe, and their language spread also. The language that they spoke would eventually give rise to hundreds of languages, among them the most commonly spoken on Earth. Spanish, English, Hindustani, Portuguese, German, Russian, French, Persian, Bengali. The list goes on and on and on.

So it's estimated that about half, so like 46% of the world's population, speaks a language that has its roots in the proto-Indo-European language. And so that's how milk-drinking shaped language across the world. There's your connections moment for the day. So even though lactose intolerance had been written about or known about for millennia, lactose the sugar was only discovered in the 17th century, and lactose intolerance only got a formal definition in the 20th century. So not that long ago, actually.

I think one of the interesting things that this has revealed is a pretty good amount of bias in medical advice. So milk was often recommended to prevent or treat certain conditions like peptic ulcers or to increase calcium or prevent osteoporosis or vitamin D or whatever else the case may be. But if you can't digest lactose, milk consumption is only going to make things a whole lot worse. But the assumption was that lactose digestion was the normal state. And so it wasn't only until recently that we have sort of learned a bit more about maybe drinking milk isn't good for you if you can't digest it. But despite this, milk consumption continues at high rates in some places and even seems to be increasing in popularity where lactase persistence is low, such as China. like China is drinking a lot more milk, the U.S. is drinking a lot less.

Yeah. So, Aaron, why don't you tell me what the lowdown is on milk today? Are there treatments besides like lactate? Let's talk about it, Aaron. We'll take a quick break first. Great. So let's reiterate to make it as clear as possible that globally, lactase non-persistence is the norm. And probably around 70% of the global population does not have the lactase enzyme

that stays on in adulthood. Okay. Yeah. Cool. Okay. But like you said, this ranges a lot across the globe. And there's a really great map. I think there's probably a whole bunch of them that we can post. But what's really interesting is so I was looking into how what milk production and consumption is like across the globe. And by far, the highest consumer country of milk is India. Okay. Like by a long shot, greater than the whole EU. and the U.S. by like twofold. And when I was looking at these maps, I was like, India has lactase malabsorption 61% non-persistence overall. And I was like, this doesn't make any sense, but then you mentioned that between the northern and southern India, it's very different.

So that's super interesting. So I wonder if they broke the map of milk consumption down if it would correlate with that. And I bet that it probably would. Yeah. That's really interesting though it is yeah but besides india um the EU the US overall actually milk consumption like you mentioned is going up worldwide so milk consumption is on the rise and milk production is on the rise globally and this is like a per capita yes yeah yeah some of the most recent data that I could find I have to say was from statista is that a good website I don't know. I couldn't get their, like, where they got their data from without signing up for an account,

and I didn't want to do that. So the other source of this info is kind of old, but it's from the FAO. So at least that's a legit source of info. But it's like 10 years old. So I don't know why they haven't updated their data in 10 years. But anyways, in any case, people. drink a lot of milk around the globe. So because we know that the normal state is lactase non-persistence, there's a lot of interest in trying to treat or manage the symptoms of lactose

malabsorption, right? And I do think that one of the most interesting pieces that I found was a number of meta-analyses that show that in general, even people who are self-identified, as lactose intolerant. So they know that drinking milk gives them symptoms can actually handle up to about 12 grams of lactose in a single sitting before they become symptomatic. Okay. So that's actually like a whole glass of milk. And it's kind of a ton of cheese because a lot of cheeses, especially aged cheeses like cheddar, have like about 0.5 grams of lactose per ounce, whereas milk has like 9 to 14 grams of lactose per cup of milk. So per serving. And lactose intolerance or lactase non-persistence is very different than allergy.

So when people have allergies to milk, it's generally to the protein, casein that's found in milk when they have a cow's milk allergy. And yes, that is very different. Okay. The other thing, though, and this is probably why products that are lactose-free have become more and more popular, even in places where lactase persistence is really common, is because the symptoms of lactose intolerance overlap with symptoms like IBS. And it can actually be really difficult to tell what is it that's causing your symptoms. Is it really the milk or is it something different? Gotcha. Yeah.

And so, yeah. So there have been a big rise in products like in products that are lactose-free. whether it's cow's milk or goat's milk that have been treated with certain enzymes, the lactase enzyme, whether it's from bacteria or yeast, that actually break down that lactose into monosaccharides, so that even if you are lactase non-persistent, you can drink that milk. You can also take it in a pill form, like we said already. And there has been some research on probiotics and things like that.

We're just not, from my understanding, at least what I've seen, we don't really have a good, another good answer. But the other thing that's become really, really popular is just non-dairy milks. Right? Yeah. So there's a lot in the United States medical literature of like, oh, we have to make sure that we drink milk because it's such an important part of our diet. Like hand-wringing at the idea of someone cutting dairy out of their diet. Right. And I think that that's, It's very interesting because, you know, the vast majority of the world can't digest dairy, and they do just fine. In the American diet, cows milk is our number one source of calcium. So if you're not drinking milk or eating cheese or getting your calcium from dairy, then yeah, you do need to make sure that you get your calcium from somewhere else. But that can be from a lot of other things that are calcium fortified or just from a calcium. supplement. Yeah. But that is the main nutrient that is found in milk that we don't see in a lot of

other foods. So most other foods that we eat have a much lower amount of calcium. Vitamin D is actually something that we add to milk because calcium and vitamin D work together in your body for bone health. So it makes sense, you know, and because a lot of us live at northern latitudes and now we wear clothes and cover our bodies so we're not making as much vitamin D because normally you make it from sun exposure but we don't expose ourselves to the sun because skin cancer um question answer so historically if people were not getting calcium from milk which probably not many people were what was happening i mean do we see a lot of the problems that we associate with the lack of calcium in like skeletal remains of people historically? So if you eat a lot of seafood or legumes or

leafy greens, these are other things that are also have good amounts of calcium. So probably in the past people just ate more things like that. So then calcium or then dairy wasn't their only source of calcium. Gotcha. Yeah. Because dairy is one of the main sources of calcium in the U.S. and in some other countries, it's thought that not getting enough dairy could lead to calcium deficiency, which is a risk for osteoporosis. But there have been some studies that have found that in places where people don't consume dairy, in places where lactase non-persistance is more common, osteoporosis is not any more common. So they're getting their calcium somehow. Interesting. Yeah. Very interesting. Yeah.

But then there is also things like cheese that have low levels of lactose because just of the way that cheese is prepared. A lot of yogurts have very low levels of lactose because the bacteria that are found in like live culture yogurt actually convert lactose to lactic acid. So there's low levels of lactose. And then, you know, there's lactose-free milk. There's soy milks and things that are fortified with almost all the same nutrients that you would find in cow's milk. there's a lot of options out. Speaking of options, we should mention that our quarantini

could be the milk in our quarantini could be swapped out for any non-dairy alternative. I love oat milk. You can use any milk you like. Yeah. You know, isn't there like they're trying to have it not be called milk

if it's from like a nut or an oat because it's like not milk? I saw something like that. It's just like this late in the game, and that's never going to catch on. Right. Plus, like, I'm not going to drink soy juice. That sounds way worse.

Oh. Well, this was a fun episode. This was a fun episode. This was a short episode. Well, it's time for one. We've had a lot of long ones lately. Yeah. All right.

Should we do sources? Yeah, we definitely should. Okay. So I read a couple of books. One was called The 10,000 Year Explosion, How Civilization Accelerated Human Evolution. by Gregory Cochran and Henry Harpending, and also a book called Milk by Mark Kalanski. And then a few articles, I just want to shout out a couple of them. The Origins of Lactase Persistence in Europe by Aitin at All 2009.

And Evolution of Lactase Persistence, an example of human niche construction by Gerbaltz at all 2011. I read a number of articles. There's a good one from the American Academy of Family Physicians that's just called Lactose Intolerance, just for some basic background on what the clinical syndrome that we call lactose intolerance is. And we will post all of our references on our website. This podcast will kill you.com for this episode and all of our episodes. Thank you so much to Katie for coming on and sharing her amazing poop story. We love to hear from you.

Seriously, thank you so much. Yes, and thank you to Bloodmobile for providing the music for this episode and all of our episodes. And as always, thank you to you, listeners, for sticking with us through all the... You know, we didn't even talk about poop that much besides Katie's bit. I know. It's kind of surprising. Yeah. Well...

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