Hi everybody.
My name is Catherine Sampson, and I met both of the Aarons and 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 defication 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 thirty 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 it's not normal,
but it'll be okay. Just shake it off, just keep 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 who 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 you 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 put 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's 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 telp people that
I'm lactose intolerant. And so I started doing that. You know, that was when I was nineteen, 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 or pants in public. That's my story, y'all.
That was amazing as always.
As always, thank you so much, Katie for your always enjoyable stories.
The best, the best not only poop stories, but definitely the.
Best poop stories. Definitely the best poop stories without a doubt. Hi, I'm erin.
Welsh and I'm erin omen Updyke.
And this is this podcast will kill you.
And today we're talking about wlacktose intolerance.
Or lack tase persistence, because really that's the.
There's so many names for this. I love it.
Oh my gosh, I think we were We're gonna have to do some sort of like a primer or briefing 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 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 quarantine of the day is truth or dairy.
And appropriately it is essentially a milk punch, So it's got milk and ram and Brandy r Kognac 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 gonna be It's gonna be another one of those episodes where Aaron can't pronounce the thing we're talking about. That's fine, I'll just say dairy.
There we go. We will post the recipe for the quarantine and the non alcoholic pluicy Brita on our website. This podcast will kill you dot 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. 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, actually 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 gonna 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 aka lactose malabsorption aka lactase non persistence aka hypolactasia. It's another term for it.
I see, I've seen all of these.
Good.
It's nice refresher.
So we know these symptoms. Eron, what are the kinds of symptoms?
Bloating, rumbly tummy diarrhea?
Do you want to know the Do you want to know the fancy word for grumbly tummy? I do? Borborygmy?
Uh? Can I get the etymology of that? Please?
Mmm? Let me google that for you. It's Greek. Great, it comes from the Greek bor borygmos meaning what meaning a rumbling or gurgling noise made by your tummy.
Wow, So it really is specifically like that word has purpose.
Amazing, I know.
Ohymas. Yeah, that's a big one. That's the medical term for a gurgly tum abdominal pain. I think you said diarrhea. 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.
So 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, well, like we're going back to the very beginning here, okay, okay, So the main function of your gi tract.
Is what to digest food.
Yeah, exactly, absorb nutrients, you know it all.
Okay.
So your gut has three main divisions, right. You have like your foe gut that's your mouth and maybe down to your stomach. Right then you have your midgut that's your small intestine, and then your hindgut, 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 choose 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 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 helped 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.
Ok. 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 die saccharide. 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.
You're good to know. Yeah, okay, And lactose is found in milk, of course, milk dairy products. I don't hear.
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 die saccharide, 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 die saccharide 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 behind. When you have undigested sugars 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 biokin We're not going to get into into fatty acids and hydrogen gas.
Uhah.
So guess what it feels like when you're intestinal bacteria start producing a bunch of gas.
I mean, whatever the Greek word you said, borberygmy, barberigmy.
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 disachrides like lactose in your colon is that it turns out that this sugar, this disacharide, it's what we call osmodically active, which means that it's
going to draw water towards it. So if you have sugar left in the lumin 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 arin If you've got a bunch of water left in your colon.
I think we both know where this is going. It's rather bashroom for some loose stool.
Exactly dirhea. As a fun side note, this is how osmotic laxatives work. So if you've ever taken merr lax 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 colony. Yeah. Okay, So 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. Wow, 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 mammal's main food source is breast milk, which has lactose, that would be pretty bad.
So this is pretty rare, okay.
And those good question. Actually I never did find I have starstar EPI numbers, and I never found good EPI numbers on this it's most common in the Finish population.
Really yeah, I know, you know, Okay, this is jumping the gun a little bit. 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 so many like lactose free or low lactose milks and yogurt and blah blah blah blah blah, we'll talk about it. Okay, great, Yeah, I was like, wait a second, but I thought, yeah, okay.
M mmm. 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, uh, 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, it's 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.
That's pretty crue.
Yeah, it doesn't happen till like after thirty five weeks of gestation anyways.
Huh.
Another way that you could end up with being not able to absorb lactose very well is if you get a GI tract infection, for example, giardia.
Wow.
Okay, that kind of GI tract 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 exactly, there's no way to write blackchase, okay, precisely.
But finally, number four, the most common way that you can have lack toast malabsorption.
I feel like people are gonna 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 in 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 erin 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 borborygmy 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 mutants.
Maybe we'll just milk mutants, milk milk mutants.
Milk mutants. But arin what you mentioned about in Finland having really high levels of seeing a lot of like lactaid type.
Yeah LA products, 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 that even people with lactose intolerance or lactase non persistence can actually tolerate about a cup or a little more than a cup, like twelve ounces of milk a day.
I was gonna make that point or like bring bring that up, that lactose intolerance and lactase non persistence 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 most 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 your 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 lactase and the little pills, the little helper pills. What do those do?
So the lactase 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 not, but that is yeast or bacteria that you can let sit in your milk and it'll digest the lactose for you. I think, wasn't it?
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 in Illinois.
You know, milk milk. I just don't hear a difference.
Quite honestly, this episode is just going to be forty five minutes of us saying ill.
Anyways, Aaron, that's it. It's what I got. That's a biology Wow.
Okay, very interesting.
That was also some of the EPI.
So are you ready to hear about the history of blacktase persistence.
That's what I'm here for.
Okay, excellent. Let's take a quick break, 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 a 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 Thalani 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 Emir 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 one.
I gotta tell you that my brain can't keep flipping between like cow milk and human breast milk, and it's 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. Yeah, 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 US in eighteen oh three, Like the first time for the purpose of keeping butter butter butter. The Cia once tried to poison Castro by slipping like
a poison pill in 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 of 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 healthwise 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, so some are loads fattier than others, like northern seals at fifty three point two percent fat. Oh my humans for reference four point five percent?
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'm imagining that in my frit 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 four percent, imagine and imagine seal milk in your fridge.
Fifty three point two percent.
Yeah, imagine that butter oh.
I mean just toothpaste consistency stock. I mean, it makes a lot of sense because if you're in the water. You wouldn't want it to just immediately diffuse or whatever. Yeah, so get wouldn't want.
You want that toothpaste milk.
Did you know also that some pinnipeds like sea lions and walrus's lactose isn't present.
Really, Yeah, so what's their main carb?
I don't know. I didn't. If we look it up, it's okay, I saw it. It's like I was like, oh, cool bit of information. That's 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'd have to have salted.
Yeah, I hope that you go to trivia night, you and anyone who is listening, and you get asked a question about milk, that this episode a key question.
The question is going to be what carbohydrate do you pinnipeds have.
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 or this whatever, this pattern has been recognized for millennia. Hippocrates in the fifth 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 suffer dreadfully.
Which is as you heard in Katie's Katie Can the test.
And Galen, who lived in the second century CE, observed and described lactose intolerance. And there were many ancient writings that advise against the consumption of milk after weaning. So why can some of us digest lactose? Approximately thirty five percent 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.
Eastern Europe the frequency of lactase persistence is between fifteen and fifty four percent, whereas in the British Isles. In Scandinavia that ranges from eighty nine to ninety six percent.
WHOA, yeah, that's even higher than I thought.
And in northern India around sixty three percent of people have lactase persistence compared to twenty three percent in the South or the East.
Aarin, that makes so much sense for something that I was reading where I went lots weird.
And in some pastoralist populations in Sudan, lactase persistence is around sixty four percent, but in a nearby non pastoralist group that number is around twenty percent. So there's a common thread here, and that thread is that lactase persistence might have something to do with pastoralism or dairy farming as a way of life. So what came first milking
or lactase persistence? 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, 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. But another hypothesis, and this one is the one that has more support, is the culture historical hypothesis, which states that lactase 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 sixty five hundred BCE in western Turkey, where lactase persistence is low to and so this suggests that milking that animals were milked before lactase persistence arose. So when did milking begin? Then milking animals probably began in the Middle East, possibly Iraq or Iran, around eight to ten thousand 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 fifty thousand 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 skills and anyway, lacktase persistence is a great example of how humans have continued to evolve.
Yeah, especially considering how widespread that a wheel 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 five thousand 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 eleven thousand years ago, followed by pigs and cattle around five hundred years after that, And so people 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, Bedowin is a really amazing musical artist. Her Tidy Desk concert is incredible. And Bedouins were traditionally nomadic and many still are, but that traditional way of life has declined. 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 pinnipeds and cetaceans just have the lowest amount of carbohydrates. Oh, it'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 was probably around eight or nine thousand years ago in Central Europe. There are different models that kind of show a variation of ranges from like six thousand to ten thousand years ago,
but that seems to be like the central accepted range. Okay, And clearly this mutation had some benefits because it's spread rapidly and widely throughout Europe in parts of Africa as well, reaching frequencies as I said, of over ninety five percent in some places. And so why would being able to consume lactose as an adult be advantageous? And there seem to be three main hypotheses for why continued milk consumption
could be selected for. And the first is that in pastoralist society, 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. 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 lactase 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 or like the age of milk?
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 in, 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.
That makes sense.
But they did find that the lactose persistence evolved in people who kept livestock, so that seemed to be the best supported hypothesis. So basically pastoralism led to the spread of the mutation that allowed for 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 lactase 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 haven't heard of that. Why 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 linguists rather than from like physical evidence. And they exist 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 the 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 forty six percent 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 seventeenth century, and lactose intolerance only got a formal definition in the twentieth 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 US is drinking a lot less. Yeah, So, Aarin, why don't you tell me what the lowdown is on milk today? Are there treatments besides like lactate?
Let's talk about it, Aarin. 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 seventy percent 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 US by like twofold. And when I was looking at these maps, I was like, India has lactase malabsorption sixty one percent 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, 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, oh.
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 there, 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 ten years old, so I don't know why they haven't updated their data
in ten years. But anyways, 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 analyzes 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 twelve 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 zero point five grams of lactose per ounce, where if milk has like nine to fourteen 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 casin 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've been a big rise in products, like in products that are lactose free, so 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 monosachrides, 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 because really really popular is just non dairy milks, right, Yeah, So there's a lot in the the United States medical literature of like, ooh, we have to make sure that we drink milk because it's such an important part of our diet, like handwringing at the idea of someone cutting dairy out of their diet, right, And I think that that'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. Cow's 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.
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 a lack of calcium in like skeletal remains of people historically.
So if you eat a lot of seafood or legumes or leafy green 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 US 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 persistence 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 level 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.
Speaking of options, we should mention that our quarantini could be 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 yeah, not milk.
I saw something like that. It's just like this late in the game. That's never going to catch on, right, It's like what.
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.
What'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 ten thousand Year Explosion, How Civilization Accelerated Human Evolution by Gregory Cochrane and Henry Harpending, And also a book called Milk by Mark Kolanski. And then a few articles. I just want to shout out a couple of them, The Origins of lactase persistence in Europe by itin at All two thousand and nine. And evolution of lactase persistence an example of human niche construction by gerbalt at All twenty eleven.
I read a number of articles. There's a good one from American Family, 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 tolerances, and we will post all of our references on our website This podcast will kill you dot 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 okay, well with that, wash your hands, you filthy animals.
M hm
Oh god, I trusted that far, way too to, way too much