Science Friday - EV Proposal, Lactose Intolerance. April 14, 2023, Part 1

Episode Date: April 14, 2023

EPA Proposal To Require 60% Of New Cars To Be EVs by 2030 The EPA released a set of proposals this week that would cap C02 emissions for new cars. In order to meet the new stricter targets automakers would need to ramp up electric vehicle manufacturing substantially. By 2030, 60% of new cars would need to be electric. Ira talks with Casey Crownhart, Climate Reporter for the MIT Technology Review, about the new EPA emissions proposals and other top science news of the week including predictions of a bad mosquito season and turtles basking in the moonlight.     Lactose Intolerance May Have A Lot To Do With Your Gut Microbiome In the animal kingdom, it’s not normal to drink milk past infancy. It’s even more rare to consume milk from another mammal. But throughout history, humans have used dairy farming as a way to get calories and nutrition from creatures like cows, goats, and sheep. And a big perk: dairy products taste good. Evidence of dairying goes back to the early Neolithic era. Traces have been found in the historical record in Europe, Asia, and Africa, in ancient teeth and pottery. Lactase persistence, or the ability to consume dairy into adulthood, developed alongside this burgeoning industry. But here’s the catch: a large part of the population is still lactose intolerant, either from childhood or developed in adulthood. It’s estimated that about a third of the U.S. population is lactose intolerant, with a higher chance among certain ethnic and racial groups. There’s a lot to learn about the origins of lactose persistence and lactose intolerance, and much of that knowledge comes from the gut microbiome. Joining Ira to talk about this is Christina Warinner, assistant professor of anthropology at Harvard University, based in Cambridge, Massachusetts.     Transcripts for each segment will be available the week after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Flato. A bit later in the hour, we're going to answer your questions about lactose intolerance and how parts of the world became so dependent on dairy and a possible role your microbiome. Yeah, your microbiome may play in lactose intolerance. If you want to get in on the conversation, we're alive today. Our phone number 844-724-8255, 844-Sci Talk, or you can tweet us at SciFri. But first, this week, the EPA released us. set of proposals that could cap emissions for new cars. And in order to meet those targets,

automakers will need to ramp up electrical vehicle manufacturing by a lot. Some 60% of new cars would need to be electric by 2030. Joining me now to talk through these new rules and other top science news of the week is Casey Crownhart, Clymer Reporter for the MIT Technology Review, and she's here with us in our New York studios. Welcome. Good to see you. Finally. Yes, in person. Thanks so much for having me. All right, let's get right to this. What's in these new EPA emission rules? These are basically new tailpipe emission rules. And like you said, they mean that carmakers are going to have to really ramp up their EV production. These rules would take effect in 2027 and ramp up from there. And the EPA is basically telling carmakers, look, of all the cars that you put out on the road, there's a cap on how much pollution they can put out.

some of that is CO2 pollution. And if they don't, they'll be penalized. So it means we'll see a lot more electric vehicles on the road. That's the only way to get up to the cap then. Basically. You could technically do fuel cell cars, but those are really, really rare still. Yeah. And so what about how do you shake up the auto industry to make them get on board with this?

Yeah. So, I mean, this is kind of adding to a growing ecosystem of EV policy. So you might remember last year the Inflation Reduction Act passed with all of those tax credits for new electric vehicles. And so this kind of adds to that, and it says, you know, hey, automakers, you need to meet these rules, even though this was kind of going this way anyway. Yeah. In order to get to that goal, we're going to have to add a lot of charging stations, aren't we?

I wrote about this this week. There are a lot of potential barriers to getting up to the levels of EVs that we need to, battery materials, for example. But I think Chargers is one of those big challenges that people are really aware of today. You know, we have less than 150,000 public chargers available. By some estimates, we'll need to have a couple of million on the road by 2030. And President Biden's Act will actually help fund those, right? Yeah, so there's been some legislation passed that helps to fund that.

But even the Biden administration's goals, they want to get half a million charges on the road by 2030, and that probably won't be enough. Wow, wow, wow. Two million, ten million personal charges in your homes? Yeah, lots and lots of plugging in to do. A lot of work for electricians. Yes, yeah. The story you brought us also is about the water usage disparities in Cape Town, South Africa. Researchers found that rich people used a lot more water than poorer people.

Tell me about that. Yeah, this was a pretty surprising finding. We know that climate change and population growth are affecting water supplies in cities, but this new study found that economic status was almost as big of a factor. So these researchers looked at Cape Town in particular, and they found that though the richest people made up only about 14% of the population, they were using over half the water in the city. So it was a pretty striking difference.

Wow. You know, shocked, shocked, rich people use more water. I mean, I'm shocked. When you think about things that they spend their money on like, you know, golf courses or big lawns, it should not be that surprising and should be applicable to the rest of the world. Yeah, yeah. The researchers said that they're not exactly sure how the specific numbers will translate, but this should be true in a lot of other places, too.

And this finding could help policymakers kind of figure out how to better address water shortages around the world. Did they have a number for how much more rich people use water than poor people? It's like 10 times more. 10 times more. So it was like around 500 gallons a day for the richest people, less than 50 gallons a day for the lower income groups. A lot of swimming pools and lawn fountains and things like that. And irrigation, yeah. Huh. And this week here in New York, it feels like we've gone straight from spring to summer. I mean, it's like almost 90 as we speak. And you know what that means? Of course, I already experienced this last night. I got my first mosquito bite. You did? Yeah. I've just sitting outside of this season. And this could be bad, a bad season for mosquitoes, right? Yeah. Yeah. I saw this story this week from an outlet called HeatMap News and it's happening already.

season could be really bad for mosquitoes. They need standing water and temperatures above about 50 degrees to start their breeding cycles and crawl out of the woodwork, so to say. And this year, because we've seen record snowpack in the West, that is a good indicator that it's going to be a bad mosquito season. Would have never thought of that. It's the flooding. So when it melts, it comes down the mountain and it floods, and then you've got a bunch of standing water around. And it doesn't take much standing water, does it? No, it's not like it needs a pond. There can be a little puddles and things, and that's where mosquitoes can breed. So it doesn't take a lot. Yeah, I heard that even in a bottle cap turned upside down. Yeah, I remember talking to mosquito experts. That's all the

water you need to get mosquitoes hatching, you know. So it's going to, it could be, it could be a bad season, especially with the high temperatures they're out and working. Yeah, it could be bad. And not only mosquitoes, but ticks are spreading beyond their usual habitats, right? Tick-related diseases on the rise. Yeah, I'm bringing you all the bad bugs this week. I'm so sorry. We're seeing more tick-borne diseases. Cases reported to the CDC more than doubled between 2004 and 2019. The majority of that is Lyme disease, but there's all kinds of diseases that ticks can spread. Alpha-gal syndrome, that red meat allergy, a few other ones as well.

And there are a few reasons for this. You know, deer populations are expanding. We're seeing warmer weather, kind of all the usual culprits. So it's that time of year. So if you're going outside, check for tick. Yeah, especially, you know, Lyme disease, right? Yeah, that one is, I think especially, in some places in West Virginia, especially, cases are exploding by like multiple 100 percentage points.

That's amazing. In certain areas, it's becoming much more of a problem than it ever was. So wear long socks up to your knees if you're not wearing, you know, you're wearing shorts? Long pants, if you can, long sleeves, wear bug spray, and check when you get home is the biggest thing. Oh, yeah, bug spray. And because those Lyme disease ticks are so tiny. You really have to check. You have to check carefully because they're small when they attach to you until they swell up with blood.

Okay. We're going to be dosing bug spray this summer. Joy. All right, let's get away from these pesky insects and arachnit. Let's talk about some undeniably charismatic creatures. Yes. And let's start off with turtles, often found sunning themselves on a log. But you're going to tell us that turtles also bask in the moonlight?

Isn't it romantic? I hear the music. What's that song about basking in the moment? I hear that. So tell us about that. Yeah, so researchers, like you said, a lot of reptiles, turtles included, they'll bask in the sunshine, helps them regulate their body temperature. But some researchers started to notice that turtles seem to be doing this at night as well. So they put together this massive study, tracked turtles in North America, Europe, Asia, Africa, Australia.

And they took hundreds of thousands of photographs, tracked 29 fresh. water species of turtle, and they found that turtles mostly around the equator tend to get out of the water and bask in the moonlight. That's crazy. I mean, because I mean, don't, don't, you know, turtles bask in the sun to regulate their body temperature. Are they getting heat from the moonlight? It seems like maybe because it is happening in the warmer places, so it might also have something to do with temperature regulation, but the researchers want to figure out why they're doing this and which kind of turtles are more likely to bask in the moonlight. Wow. So you could go out at night now and maybe see turtles basking in the moon.

Mostly if you're close to the equator, but yes. I've got to weld it. Let's take a trip on that. The final story you have is this is another delightful animal behavior. Until I saw, or you say go watch the video on this, you're not quite sure how this can happen. And this is an elephant at the Berlin Zoo figured out how to peel a banana. Yes. Yes. This is. I can think that your feet, the elephant's feet, could be fine enough to peel a banana, but that's not how they do it? No, she does it with her trunk, so she kind of picks it up by the end and, like, sort of flicks it.

This is not a common elephant behavior. It seems like she picked it up from her caretakers that, you know, raised her and would feed her peeled bananas. My favorite part of this story is she doesn't do it all the time. She only does it when the bananas are yellow with some brown spots on it. So only certain bananas she'll peel. So she knows when it's ripe. Yes. She can tell when it's ripe. And she won't do it around other elephants either. It's just like she'll eat the bananas with the peel on when she's with other elephants. And then she'll save one and go and peel it later by herself. Is she showing off her people? Do people actually at the zoo watch her do this? I don't know if she's done it in front of like guests at the zoo. But the researchers got video of it, which is what I'm saying, you need to go see this video. It's wild.

So how does she do it in the video? What does she do in the video? How does she actually peel it? She picks it up with her trunk by the end of it, and she kind of like flicks it so that a piece of the peel kind of comes off, and then she kind of repeats the process. Kind of like how you would peel a banana. You know, you'd take one chunk of it and you peel the peel down. She's basically doing the same thing. Her next act, peeling a grape, maybe. That I would like to see. We have a few minutes to talk with you.

What other kinds of projects are you working on? What's your next story that you might be working on? Oh, I actually just published one this week that I had a lot of fun. working on. It was about a new way that people are trying to store energy in heavy industry. So a lot of manufacturing processes, they need a lot of heat to run, whether it's like food processing or making steel. And a lot of that is fossil fuels today. So a couple of companies, what they're doing is they're taking renewable electricity when it's available, like when the sun is shining, and they're using it to heat up stacks of bricks.

Stacks of bricks. Yep. It's stacks of bricks or other kinds of blocks that are made out of other materials. And so these bricks can get super, super hot, like over a thousand degrees Celsius, and then they can use the heat later on. So are the bricks in the room with you, or are they? They're in like a separate container. It's a very well insulated, like steel box, basically. Well, because I've heard about water. You know, water is a great story. You know, that people making columns of water in a room and the sun will come in. It's like passive radiation. This is not passive. It's not passive. It's sort of like the mechanism that's in your toaster. like you run electricity through the toaster coil and it heats it up. It turns electricity into heat.

It's the same sort of thing. So it has a little coil in there that heats and then the heat radiates through the bricks. Is this is just in its testing phase? You can't go out and buy a brick heater. You can't buy a brick heater just yet. There are a couple of companies that have pilots running or they're working on it. There's one called Rondo Energy out in California that just started up their first commercial pilots. You know, I love to watch necessity forcing invention, right? It's fascinating. What I love about it is it's such a simple idea. It's a stack of bricks, and it's just one of the possible solutions.

Thank you, Casey. Great way to top off our discussion. Thanks so much for having me. Casey Crownheart, climate reporter for MIT Technology Review. We have to take a break, and when we come back, we're taking your questions about lactose intolerance. Our number 844-724-8255, 844-Sight talk. Also tweet us at SciFry. Things you want to know about lactose intolerance, it's history.

Maybe you've always, you've have it in your family. We can't take any medical questions, but we'll talk about it in general. Stay with us. We'll be right back after this short break. Hey there, podcast listeners. I were here with a simple request. If you're listening to this podcast, learning something, enjoying yourself, please go to ScienceFriiday.com slash support to make a donation.

Our work and this podcast depends on public support from listeners like you. You know that. You're here listening, which means you find our programming valuable. Any amount makes a difference, even two bucks. But the lasting gifts are the ones we can count on sustaining donations, which we can rely on every year. So please go to sciencefriiday.com slash support to make your gift. Again, that's science friday.com slash support.

And thanks. This is Science Friday. I am Ira Flato. My physician told me the other day that she suspect that I may be lactose intolerant. Now, that's not uncommon to debut in the later years, and I'm staying away from dairy for a while to test this out. And you know, you know, it's not an easy thing to do to stop eating dairy products, cold turkey. Because here in the old U.S.A, we love our cold glass of milk, our ice cream.

Oh, and I'm going to miss that cheese. But everyone can enjoy these creamy treats. Not everyone can enjoy these creamy treats like me. If it's true, it's estimated that 30 to 50 million Americans, that's a big number, 30 to 50 million are lactose intolerant. and your chance of being lactose intolerant depends on a lot of factors, including race. Now, does that mean lactose intolerance? Lactose intolerant people can no longer enjoy an ice cream cone? Well, that among other questions is what we'll be discussing in this hour.

We call, what's the deal with lactose intolerance? And joining me to tell us about it from the history to modern treatments is my guest, Christina Werner, Associate Professor of Anthropology at Harvard in Cambridge, Massachusetts. Welcome back to Science Friday. Thank you for having me. Nice to have you. Our number again, 844-724-8255. If you want to talk about lactose intolerance, if you want to hear from you, we can't answer

any personal medical questions you have. That would be unethical. But there is a really rich cultural, biological, and historical history of lactose intolerance that we can't talk about. So what do you want to talk about? You make the call, only if you make the call. Our number 844-724-8255-844-SyTalk or tweet us at SciFry. Let's get right into this from the very beginning.

Let's start with a definition so that we're all on the same page. Christina, what exactly is lactose intolerance? So lactose intolerance are a suite of symptoms that some people experience when they consume lactose. Lactose is the major sugar within milk, and the typical symptoms. Symptoms include things like diarrhea, cramping, and general discomfort. And what's happening in the digestive system when someone who's lactose intolerant eats ice cream, for example? What's going on in there? Well, so lactose being the main sugar in milk is consumed by all mammals.

Mammals consume milk. This is something that all mammals can consume in infancy. But actually, the natural state of mammals is to progressively stop producing lactase. enzyme that breaks down lactose as you age. It's part of the weaning process. And so actually, lactose intolerance or some of the symptoms of lactose intolerance, reflect this sort of natural state of humanity that at a certain point you'll stop drinking milk, you will no longer produce the enzyme that digests it. And what ends up happening is then the lactose passes through your digesto track. It goes into your large intestine, where your gut microbiome is, and there the microbes will

happily digest it for you. However, unfortunately, they digest it by fermentation. And in doing so, they produce gases and acids which can upset your gastrointestinal tract. However, because the gut microbiome differs from person to person, there's variation in lactose intolerance symptoms. And it's obviously not a rare thing. If I said before, 30 to 50 million people? Wow. Yes, it's very common worldwide. As I said, it's actually, the natural state of humans and mammals in general. Initially, lactose intolerance was presented as a kind of pathology, but we now know that it's not actually pathological.

In fact, it is rather certain mutations that some humans have acquired throughout human history, human prehistory that have changed their ability to digest lactose, allowing them to digest it longer into adulthood. We call that lactase persistence. So those people continue to produce the digest. of enzymes that they did win an infant throughout their whole lives, making them more tolerant of milk sugars. You studied a fascinating case of Mongolia.

According to their DNA, people of this region should be lactose intolerant, but this is a big dairy culture, right? What's going on there? Exactly. A lot of people don't know about the dairy history of Mongolia, but it's absolutely fascinating. So in Mongolia today, people there milk more species of livestock than any other place in the world. So they dairy the common dairy livestock species, so cattle, sheep, and goats, but also yaks and horses and camels and even reindeer. What's very interesting about Mongolia is that

people there do not have the genetic mutations that are known to enable lactose digestion into adulthood, and yet they have a dairy-based diet. And what seems to be happening there is a gut microbiome adaptation to long-term milk consumption. Because they're surrounded with soft. many elements for your microbiome from all the lifestyles they do. I mean, the animals, the soil. Well, they have a really long history of daring. So we can trace the history of daring in Mongolia back to approximately 3,000 BC when it was introduced by migrating herders from the West. And so there's a long and continuous tradition of daring in Mongolia. However, as people move to the city and live more urban lifestyles, lactose intolerance is increasing because this gut microbiome

adaptation, it's not permanent or fixed. It really depends on the diet that you consume. So could that be part of the problem of 30 to 50 million people that our microbiome needs a little tinkering with? Yeah, so lactose intolerance is not kind of an on-off state. It actually exists on a spectrum. So some people who have these genetic mutations that allow them to produce the enzyme lactase, what that means is that the lactose that they consume gets broken down into their small intestine such that their large intestine just really never sees it. So they never experience those symptoms of lactose intolerance. But many people lose that ability to produce the enzyme, and then they have this sort of variable response. The population that has the highest amount of, or the

highest rate of lactase persistence is Scandinavians, where approximately 80% of people produce this enzyme for their entire life. And then it declines from there. However, it's not limited to your So we know that there are at least five different mutations that have arisen throughout human history in different parts of the world that occur, for example, in Europe, in East Africa, and through parts of the Middle East. Lots of people are calling 844-8255. Lots of folks are also tweeting us. We have Natalie from Houston who wants to know if lactose intolerance is impacted by age. to some degree, yes, in part because your microbiome changes as you age, and so it will respond differently to the lactose that you consume. So you can, a lot of people experience, increase lactose intolerance as they age. However, I will say one thing that's important is that different dairy products have very different amounts of lactose. So milk has a high amount of lactose,

ice cream has a high amount of lactose, but things like aged cheeses actually have very little lactose. So sometimes people become confused about whether or not they actually have a lactose sensitivity or another sensitivity to, for example, the proteins within cheeses and other dairy products. Which one of the aged cheeses I'm wanting to know now? Well, most of the aged cheeses actually have very little lactose. So Parmesan has almost none. Also, even some of the aged soft cheeses like Brie have almost no lactose. Wow, wow, that's good to know. Let's go to the phones. Let's see what kind of questions we have there. Maryland, welcome to Science Friday.

Hi, good afternoon. Hi there, go ahead. So I was just going to bring up the point that I have a few friends that are lactose intolerant, and whenever I introduce them to goat milk and goat products like goat butter and goat ice cream or sheep, same same, that they process that completely fine, but they cannot handle cow lactose anymore. Wow. Yeah, that's really astute. Actually, a lot of people don't know that different milks are compositionally quite different.

They have different proportions or different amounts of lactose versus proteins versus fats. And for example, sheep milk is quite high in fats. And it is known that when you consume lactose in association with high amounts of fat, it actually slows down to the digestion. So even if you're producing very little enzyme, it gives it more time to act and will reduce the symptoms of lactose intolerance. That's why a lot of people who are, have sensitivity to lactose and maybe can't drink, glass of milk might be able to tolerate ice cream better because, again, the fat that's in the ice cream actually slows down digestion and improves your ability to metabolize the lactose. Kenny, thanks for that observation.

Absolutely. Have a good day. Yeah. Danielle on Twitter says, I've noticed that long periods without milk, I can then tolerate small amounts of milk. Does the enzyme replenish in the gut? Oh, that's a great question. So the enzyme doesn't seem to react at all. to or change it all in terms of how much milk you consume. So the enzyme is continuously expressed in infancy and then in most people declines through childhood, independent of how much milk they're consuming. But for those individuals that have lactase persistence or these mutations, they'll just maintain this constant high level of lactase production. So that's not what's

changing if you experience these kind of differences. More likely, what's changing your response to lactose is changes in your microbiome over time, because your microbiome does react and respond to the foods that you eat, because the foods that you eat are its major food. Have we been able to identify which bacteria or microbes are in our microbiome that would be beneficial to help us digest the lactose? That is a great question, and there is a lot of work going on to address exactly this question. We do know that certain bacteria are milk specialists or they tend to really thrive in the presence of milk. There's an entire group called bifidobacteria.

These bacteria are especially abundant in young children and infants where they completely dominate the gut microbiome. But many people will maintain smaller populations of this group of bacteria into adulthood if they continue to consume milk. We don't exactly know what role, however, they play in adult milk digestion. Let's go to the phones again because we got some really interesting phones. One from Tracy and Merritt in Connecticut. Hi, Tracy. Hello, thanks for taking my call. Go ahead. Nice to have you. I was speaking so much. I was wondering about raw milk because I had heard and said that those with lactosensitivity can oftentimes tolerate raw milk as opposed to pasteurized.

And that's been true for me. So I was curious what you had to say about that. It's a great question. So raw milk, still contains microbes, and those microbes contribute to the fermentation of lactose. So one thing that's really interesting is, you know, for most of the period during which humans were daring, they didn't have any way of pasteurizing their milk or preserving it. So if you milked a cow in the morning by mid-afternoon, it would already be turning to yogurt because it's going to be fermenting from those bacteria. And what those bacteria are in part doing is they're consuming the lactose, and they're producing

lactic acid, which is souring the milk as a byproduct. And so when you're consuming raw milk, you're intaking higher levels of those lactic acid bacteria that help to break down the lactose. So that might be contributing to reducing somewhat the lactose content, but different raw milks contain very different amounts of lactic acid bacteria, depending on how the animals are raised. Tracy, do you consume raw milk regularly? I do. I get it from a local farm here.

All right. Thanks for calling. Thank you so much. That was interesting. Thank you. What do we know about how the tolerance for milk drinking developed, Christine? Oh, this is a great question, and this is something I have spent the last 10 years trying to work on. It's a very hard problem to answer if you think about it. Milk, as you might imagine, does not preserve very well in the archaeological record. It is a liquid. It decomposes very quickly. But it turns out that it does leave a few trademps.

races behind. For example, milk fats will become embedded in ceramic pottery and different vessels, and those can be recovered to try to track milk throughout the archaeological record. And what I've been working on in particular is that the dental plaque on the surface of your teeth actually becomes coated with milk proteins. That calcifies while you're alive. It's actually the only part of your body that fossilizes while you're still alive to form tooth tartar, which is the material you go and have your dental hygiena scrape off. But embedded in that tooth tartar are these milk proteins. And so one of the things you can do is study those proteins in the milk,

and we can use that to actually track the origins and spread of dairying. We know from this sort of research that dairying is at least 9,000 years old. It begins in the Near East, although where exactly we are not precisely sure, it is going to be somewhere near Anatolia, which is where present-day Turkey is, or along the Levantine coast, kind of in this general region, we believe, is where daring begins. And from there, it spreads. It spreads into Europe. It spreads south into East Africa. And then it spreads eastwards into Asia. Wow, wow. Wow, that's fascinating. Fascinating talk with Christina Warriner, Associate Professor of Anthropology at Harvard University in Cambridge. We're talking about

Lactose intolerance. Das on Twitter says, as a South Asian, I noticed many of us are lactose intolerant. Do you know why? Yes. So the genetic mutations that allow lactase to be produced as an adult, they are present in some people in South Asia, but it's not at a very high level. So most people of South Asian descent do not produce the enzyme as adults, and so are more susceptible to becoming lactose intolerant. And this has to do these mutations themselves spread

during prehistory through known human migration and interaction events. So what you're experiencing is not uncommon. Lactase persistence is more common in the north than in the south, for example, within the Indian subcontinent. And that's because? That has to do with the specific population and migration history of India. Are there different ways lactose intolerance develops in people? I mean, Does some people get it right away? Does it come in later life with other people? Yeah, that's a great question. Yes, it presents itself in a fairly heterogeneous way. Some people are very sensitive. Others are much less sensitive. One thing that is really interesting, there have been studies, scientific studies, trying to understand if, for example, prolonged milk

consumption will change your response, and it does. So for people who have, even people who have fairly severe lactose intolerance, if they continuously consume high amounts of dairy. That sounds very unpleasant, and I'm sure it is to undergo. But after about a week, those symptoms will subside and they'll no longer experience diarrhea. What's interesting is in Mongolia, they actually have a type of cure that people go onto or a kind of treatment. If they're having gastrointestinal upset, well, they'll consume high amounts of dairy for about a week, and they find that they have, they use this as a kind of purification

means and after that they have improved dairy digestion. Do we know why that is? We believe it has to do with changing the gut microbiome by feeding the gut microbiome, high amounts of lactose. You actually shift the ecology or the proportions of the bacteria that are present. But narrowing down which specific bacteria are responsible is really tricky because there are more than 1,000 different bacterial species within the human gut. If you listen to the show, you know we love to talk about the microbiome. So I'm glad we're talking. about it. We have to take a break, and when we come back, we'll take lots more of your calls about lactose intolerance on number 844-724-8255, talking with Christina Warrner,

Associate Professor of Anthropology at Harvard in Cambridge, Massachusetts. Stay with us. We'll be right back. This is Science Friday. I'm Ira Plato. We're talking about the history of dairy consumption and the science behind lactose intolerance with my guest, Christina Warriner, Associate Professor of Anthropology, at Harvard University in Cambridge, Massachusetts. And, of course, we want to hear from you. Lots of people interested in this. 844-724-8255. That's 844-Sy-Talk or tweet us at SciFry.

And since we have a lot of folks on the phones, let's go to the phones. Let's see who we're going to go. Oh, let's go to Carol in Chicago. Yeah, Carol in Chicago. Welcome to Science Friday. Hey, Ira. Hey there. I heard you were just diagnosed, and I, possibly, and I wanted to take you out of your misery because I've been lactose intolerant for a long time.

And there are these over-the-counter lactate pills. They're like fast-acting. You take one before you eat cheese, ice cream, whatever, pizza, and you have no problems. Wow. It's a miracle little thing. I'm doing it for like 20 years. It's amazing. it works. Great recommendation. Christina, why does that work? Well, it's mimicking the production of

lactase that would occur naturally in your small intestine, so it's just replacing that function. So yeah, taking lactase enzyme pills in association with consuming dairy is a great way to minimize or eliminate the symptoms. Now, for the other side of the story, let's go to Rachel in Brooklyn, New York. Hi, Rachel. Hi, thanks for taking my call. I've been lactose intolerant for about 10 years. since I turned 25, I guess a little more than 10 years. I have a very strange presentation of lactose intolerance from what I've discovered in talking to other lactose intolerant people. I get stabbing pains in my stomach.

I don't have a lot of gas or diarrhea, but a lot of pain. And interestingly enough, lactate pills do not work for me, and I have no idea why. I've also been curious noticing the impact of different types of dairy, products on my stomach. Melted butter is the worst. Melted cheese is extremely painful, but cheese that's not melted for some reason is less painful. I just don't really know why. All right. Let's get a reaction for Christina. Why might lactate not work for some people? It sounds like your intolerance might not be to the lactose itself, but to something else,

because butter should have virtually no lactose whatsoever. So I suspect you might have an intolerance to another part of the dairy product. And I talk to your doctor about that. Yeah, we can't answer that one. But we can talk to Laura in Quincy, California. Hi, Laura. Yes. Hi, go ahead. You're on Science Friday. Well, I became lactose intolerant. I'd say it was probably in my early to mid-30s. Went to the doctor. He told me to avoid all kinds of stuff. And I avoided milk, and that was better. But then I went three years not eating gluten. And the the lactose intolerance is gone. So what you thought was actually lactose intolerance turned out to be gluten intolerance?

Yeah, and it made me lactose intolerance. Wow. Diarrhea was the symptom. Christina? Yeah, I think what you're describing is not uncommon. What's interesting is, so as I mentioned before, the symptoms of lactose intolerance are actually caused by how your microbiome responds to lactose. and depending on the composition of your microbiome, it can respond in different ways, whether it makes hydrogen gas, which makes you feel particularly bad, or if it makes you produce, for example, carbon dioxide gas, which can make you feel bloated, but is not associated with the severe symptoms.

Gluten also, the symptoms to gluten are also caused by a response to your gut microbiome. So it's how your gut microbiome does or does not process gluten also really strongly impact. the degree of symptoms you might have or the degree of response you have to gluten. So in both cases, those are two well-known food components where the microbiome plays a really large role in the particular symptoms you might have of intolerance. Speaking of the microbiome, probiotics and prebiotics, right? They're a bit of a buzzy field right now. There have been some studies that show a positive correlation between probiotics and the ability to digest lactose. Do you think these aren't promising? I think it is complicated and often a lot more complicated than

advertisements make it seem. So the things that we call, so probiotics are bacteria that can potentially aid in digestion. And so things like yogurt naturally come with these probiotic bacteria because they're the bacteria that are digesting the components of milk. And so the thing about probiotics, though, is that they have a very hard time, surviving in your gastrointestinal tract. So first they have to go through your stomach, which has a pH of two. It's a super acidic, so they have to survive that. And then they have to be able to make it to your colon and establish themselves,

which is very hard to do because it's fully colonized with other bacteria. In cases where it seems to be helpful, you have to take it with the food they actually consume. So they have a much higher chance of survival if you consume a probiotic, for example, in its natural food. So with yogurt, the yogurt itself helps protect the bacteria from being destroyed by the acid in your stomach. And then once they're in the colon, it actually helps to feed them so that they can survive. So probiotics work really well when taken in combinations with the kinds of foods that feed them. But if they're taken in isolation, they have a really hard time surviving and establishing themselves. Now, as you were saying, not every region of the world has a culture of milk drinking.

where do we see a lot of historical milk consumption? So it begins, as I said, in the Near East and Anatolia. So kind of the eastern Mediterranean is where milking seems to begin, but it isn't a really large component of the diet. What's interesting, too, which is, I think, one of the most fascinating puzzles that's come out of recent ancient DNA and archaeological work is there's about a 4,000-year gap between when daring first is invented

and when the first genetic mutations arise that allow people to produce lactase for longer. So you can kind of think of it as effectively all of the original people who were consuming and making dairy products were effectively lactose intolerant in some way, and yet they could still do it. They were not just being, we wouldn't know that they're just in pain and eating and drinking dairy products. We suspect that they weren't in serious pain, but they didn't have any special adaptations to it. they didn't have any of the genetic adaptations. I suspect that what is helping them is they're consuming fermented products, as I said, in the absence of refrigeration and in pasteurization, even within a few hours,

raw milk will start to sour and already start to turn itself into kind of yogurt and cheese-like products. And so there's a natural reduction of lactose from that. And also they would have been utilizing much higher fat dairy products, and that also aids in the digestion. But it begins in the Near East, but where it really becomes important and where it comes to dominate the diet is actually in a region called the North Caucasus. This is a region between the Black Sea and the Caspian Sea. It's a really harsh region. You can't grow agriculture there.

And what ends up happening is people end up moving their dairy animals who were previously farmers where maybe the dairy made up a minor portion of their diet. it. They end up moving into this region and becoming full-time pastoralists, so just taking care of their animals. And they become the world's first fully mobile pasturists, meaning they have no permanent settlements, but migrate with their herds to access different pastures. This occurs approximately between 6,000 and 3,000 years ago. There's this increasing intensification, and they are really the first population to really intensively utilize milk. They then invent the wagon and many other technologies associated with the wheel, and that population expands both westwards into Europe and eastwards into Asia, and they spread this dairy technology. And it's from this sort of bronze

age expansion that dairy spreads to much of Eurasia. Would we suspect they became more tolerant then of lack of what's, of the milk and the dairy products to so widely spread it around? That's a great question. We do believe that one of the known mutations originates in these populations, but at the time when they're doing this, it's at a very low level. So this becomes a real question. It's actually later during the late Bronze Age and Iron Age that the levels of these mutations really start to increase in human populations, and we don't know why it's so late and why it doesn't seem to be necessary during earlier periods. This is a real mystery. And is there a place that no one drinks milk? Now we don't see a lot of milk drinking going on.

Yes, there's many places around the world. So Daring was never, developed in the Americas, for example, prior to European contact. It was never developed in Australia or in Oceania. But dairy does spread to large parts of Eurasia and Africa through these historic migrations and expansions. Interesting. Let's go to the phones. Claire in Wadebridge, Vermont. Hi, welcome to Science Friday. Hi. Hi there. Hi. Hi. I have a question about the enzyme you were talking about that is related to sustaining an ability to digest lactose. And I'm wondering how that is detected and whether it could be or already is part of a routine health screening.

Yeah, she's from a cheese state, so she wants to know this. Yeah, so there's two ways you can do it. So you can take a very simple genetic test to tell you whether or not you have the mutation that allows you to produce lactase. But more commonly in a clinical setting, people will take something called a lactose. challenge test. That doesn't exactly measure the enzyme directly, but a little bit more indirectly. So what you do is you consume lactose sugar in water, and then you breathe into a machine that measures the amount of hydrogen breath for the next two hours or so. And if the lactose passes

very quickly into your colon, which will happen if you don't have lactase production, then generally the bacteria will start to produce hydrogen gas, and so you can measure that non-invasively by measuring your breath. So that's the typical clinical test, but the problem with that test is it really does depend on the composition of your microbiome, so there is a bit of noise and a bit of air. So the more straightforward way to test for it is just to do a simple genetic test. Interesting.

Thanks for the question, Claire. Thank you. You're welcome. Does the origin of a dairy product change how our bodies react to it? Like, would my gut microbiome react differently from, let's say, ricotta from Italy than to cow's milk from Brazil? Oh, that's a great question. I'm glad you brought up ricotta because ricotta is a really unusual dairy product. It's actually not a cheese.

So most cheeses are what we call cheese are typically essentially curds. So it's the casein proteins in milk, which is a group of proteins that are easily coagulated to form the curd. if you remember like the nursery rhyme of Little Miss Muffet, so I don't know if it eating her curds in way. So that curd is what we use to make cheese. The way, the part, the liquid that's left behind after you make cheese actually still contains proteins. They're just dissolved so that you can't see them.

But if you process it much, much more, and it's really quite difficult to do, you can force those proteins to fall out of solution and then to coagulate, and then you can turn that into ricotta. Wow. This is Science Friday from WNYC Studios. Where you get to learn all about ricotta cheese like you never thought. It's fascinating.

Yeah, and the different dairy products, I mean, I think in the United States, we're very familiar with a fairly narrow range of dairy products, mostly of European origin. But if you take a broader view, the number of different dairy products that are produced globally are incredible. For example, throughout Central Asia and Inner Asia, one very common dairy product is made by fermenting mares milk or horse milk. This is called Kumis throughout much of Central Asia or Iraq in Mongolia. And this makes a kind of alcoholic milk beverage, which is really widely enjoyed. That's not the only alcoholic beverage you can make from milk. Also in Mongolia, they make another type of dairy product called Chimin Ark, which is a type of distilled yak yogurt.

And so there's many different products that you can make. One of the reasons, though, that horse milk is so widely used to make alcohol is that, of all the dairy animals, it actually has the highest lactose content. So it has the highest potential to produce alcohol. Well, what don't you know yet that you'd like to know about? You seem to, wow, there's wonderful little tidbits from all over the world. What would you like to know that you don't know yet? Oh, I want to know so many things. One of the things I really want to know is where exactly milking begins and how it spreads. And this has been something that I am working on. I have a really talented postdoc and student working on this problem.

But that's one of the biggest questions I have. But also, I am just absolutely perplexed by the fact that we have so much milk drinking. You have the creation of dairying systems. You have the expansion. You have even entire populations that are relying on milk as their primary dairy product. And yet we don't have lactase persistence for much of this period of prehistory. And then suddenly around the Iron Age, the levels of lactase persistence, this mutation spreads like wildfire. And we don't know why.

And by the medieval period, for example, in Europe, it reaches present-day levels, which are pretty high. And what the process was is just completely elusive. How do you find that out by scraping the teeth, the tartar off of old teeth that you do? Yes, I think that's the brute force way I'd go about it is to reconstruct genomes across that period of time, to try to understand the exact scale and the speed at which those genetic adaptations are changing. and then in parallel to measure how much milk protein we have, there's got to be an answer, and I think we just have to put together a really good team to solve it.

Well, it's going to say it doesn't seem to be a whole lot of people who are as interested as you are in doing this. Enough people? Yeah, I think it is actually an area of great interest. I mean, this is actually a question that archaeologists and anthropologists have been debating and discussing for a really long time. And we keep coming back to it, because on the one hand, it seems like a simple problem we should be able to solve,

and yet it remains elusive. Is it, do you lack the tools to find this, to nail this down, or just being lucky in finding something that will pop out of some of your research? Well, I think a big change has been new technologies becoming available. So, as I said, for a long time, it was just very hard to directly detect milk, and so we used a lot of indirect methods. The ability to detect milk proteins has been around for less than 10 years.

So this is something that's really ramping up, and I'm hoping that this will help resolve a lot of these longstanding questions. And so we're going to be hoping that you could find out about the history of milking. Where's the first place it started? That's what you want to know. Well, I want to know, yeah, a little bit.

I want to know. And I also want to know how it spreads into Africa because the trajectory of milking in Africa is also extremely interesting. And also milking in the Arabian Peninsula also takes on an entirely different trajectory where it seems to be associated with camel milking. And one thing that's really interesting there

is that camels have a greater tolerance for salt in their water than humans do. So camels can tolerate saltier water than humans. So a lactating camel can function as a kind of desalinization plant for humans that are trying to cross a desert because finding freshwater oases is really difficult. They're spread out.

But if you have a lactating camel, you can access them. What a way to stop and end this conversation. Thank you for taking time to be with us today. Thank you. Christina Warrener, Associate Professor of Anthropology at Harvard. And that's all the time we have for now. Lots of people help make this program happen. We had helped this hour from audio engineers Lisa Gosselin and Kevin Wolfe.

Annie Niro is our individual giving manager. Beth Ramey is our controller. Velasah Mayors is our office manager. and BJ Leederman composed our theme music. And of course, if you missed any part of the program, you'd like to hear it again, subscribe to our podcasts or ask your smart speaker to play Science Friday.

Have a great weekend. I'm Ira Flato in New York.