SciShow Tangents - Milk

Episode Date: August 18, 2020

Milk is pretty normal, right? Boring even! But have you ever thought about it? Like, really thought about it? We have! And I gotta say, it led us to some challenging places. Follow us on Twitter @SciShowTangents, where we’ll tweet out topics for upcoming episodes and you can ask the science couch questions! While you're at it, check out the Tangents crew on Twitter: Stefan: @itsmestefanchin Ceri: @ceriley Sam: @slamschultz Hank: @hankgreen 

Hello and welcome to SciShow Tangents, which is a lightly competitive knowledge showcase starring some of the geniuses that make the YouTube series SciShow happen. This week, as always, I, Hank Green, am joined by Stephan Chin. Hey. Stephan, what's your tagline? The chicken is in the coop. I repeat, the chicken is in the coop. Sam Schultz is also here with us today.

Hello. What's your tagline? A big pile of rocks. Man, the world is heavy right now Sari Riley is here with us as well Sari have you been getting enough to drink? yes I have my water bottle here

I think today I have definitely sweated out more than I have consumed so I'm probably dehydrated yeah it's hot here it's so hot it's like 100 freaking degrees. Oh, man. We should all go down to the lake independently by ourselves. Sari, what's your tagline?

Surf's up. Nice. And my name is Hank Green, and my tagline is, can you dig it? Every week here on SciShow Tangents, we get together to try to one-up the maze and delight each other with science facts, things that are just true about the universe. We're playing for glory, but we're also keeping score and awarding sandbox

from week to week. We do everything we can to stay on topic here on SciShow Tangents, but judging by the last 30 seconds, we won't be great at it. So, if the rest of the team deems your tangent unworthy, we'll force you to give up one of your sandbox. So, tangent with care! And now, as always, we introduce

this week's topic with the traditional science poem this week from Sari. From mammary gland and secreted from teat, to paraphrase Marge Simpson, I just think it's neat. Milk gives nutrition to babies, but that is just the beginning. It's

much more than fat. From biochemical signals to bacteria for the gut, it's social and psychological and honestly what makes us want to drink cow milk or digest lactose? The questions seem endless if you look close. And it's not crop milk or milky almond goo. It's an adaptation that unites every mammal to you. So I guess in a sense, milk evolutionarily rules. Plus, we can call it moo juice, which I don't know, I guess is cool. I mean, we can call a particular milk moo juice. You can call all milk moo juice if you want. Yeah, that's true.

You're right, that's true. Absolutely. Almond moo juice yeah you can call all milk moo juice if you want yeah that's true you're right that's true absolutely almond moo juice oh yeah language is language is fluid yeah as the as the regulators who would like to make it so that we can't call almond milk milk should know this is a current debate happening in government because the milk industry is not happy about all the plant milks if they proposed a better name but i i thought that they wanted to call it nut juice, which is like not appetizing. No, can't do that. Can't call it nut juice. I mean, milk is also pretty gross.

That's true. Just the idea. And what I like about almond milk and the other plant milks is that they have, and I get to tangent as much as I want because I can't win this season, is that you have separated the idea of like a biological secretion from i do occasionally still sometimes put on my cereal i want to separate the idea of what milk is from the fact that it came out of a teat well milky also like there's the word milky to describe other things and i don't know which came first oh i think milk the secretion came first would be my guess yeah probably and then milky things that looked like milk but anyway i feel like all the nut juices all have that same milky consistency which is why should we call them almond milky soy milky cashew milky that's really cute i like that that's fun yeah was milk the second beverage ever water Water first, then milk? So like fish were drinking down there in the ocean.

Yeah, just water. But the mammals were like, I came up with a new beverage. I bet something sucked blood before the first mammal. Oh, shoot. It's gotta be blood, you're right. Third beverage, milk. So Sari, do you know what milk is? We've been talking about it a little bit.

It is something that unites all mammals. Milk is the nutrient-rich liquid produced in the mammary glands that is a source of nutrition for infant mammals. A milk scientist reached out to me on Twitter to be like, don't fall into the trap of just saying milk is nutrition. So this is me saying milk is way more than nutrition. There's like biochemical aspects to milk in that it helps build infants' immune systems and convey chemical signals, like even hormonal signals from mothers to children. There's like a social aspect of it because like the fact that humans drink milks of other species is weird, relatively speaking, as far as mammals go.

Okay, and do you know the etymology of milk? Not milk, but I do know milk. Okay, a lot of people do say milk, and that troubles me. Well, I hate to break it to you, Stefan, but the Proto-Indo-European root is melg, which means to wipe, to rub off, to stroke, to milk, in reference to the hand motion involved in milking an animal. So before humans harvested it, this substance had no name.

Well, that's true of all things. I don't think so. If they saw other animals drinking it, and they didn't think, I should name that stuff. It was just a nameless white thing. Well, it may have had a name, but we didn't have the word milk until we had we were stroking it out of cows yeah it probably had a name in in various languages

when it was like when when you're breastfeeding a baby or something like that like there's probably a word for that specific but it has no connection to the word milk that we use now to describe this humans have milk too i forgot about that yeah even the origins around the the word milk that we use now to describe this humans have milk too i forgot about that yeah even the origins around the word milk are kind of mysterious because there's another proto-indo-european root galag or galag which is where we get like galactose or like galaxy lactation things like that oh because the galaxy's milky. It's milk. Wow. But it says the absence of a common word for it is considered a mystery.

So really, my guess is, Sam, that everyone had a different word for milk and then for some reason, milk won. Now it is time for Truth or Fail. One of our panelists has prepared three science facts for our education and enjoyment, but only one of those is a true fact. The other panelists have to figure out which one is the true fact.

And if we do, we get a Sam Buck. If not, then Sam will get the Sam Buck because Sam is presenting the facts for us today. Sam, tell me your three facts. If you aren't lactose intolerant, cow's milk is generally seen as a nice, safe, boring drink. But sometimes cows can eat something which can turn plain old milk deadly. Which one of these is one of those things?

Number one. Cows chew cud. They can't get enough of the stuff. But there are some grass species that, during this fermentation-y process of ruminant digestion, releases poisonous compounds, including cyanide. While it isn't a large enough dose to harm something as big as a cow, it can end up in the cow's milk, where it can cause severe illness

and even sudden death. Two, sweet potatoes are a fairly common part of many cows' diets, but if a cow eats too many of them, it can cause big trouble for people. Indigestible sugars from the potatoes can accumulate in the milk, and when this sugary milk is drank by humans, it can overfeed the gut microbiome, leading to severe malnutrition and even death. Or, number three, throughout the American Midwest, you can find an unassuming white-flowered herb known as white snake root,

which happens to be incredibly poisonous. If ingested by cows, their milk is contaminated by the toxin, making the milk harmful and potentially deadly. So we've got three different ways that maybe milk is deadly, and two of them are made up. We've got some grass species that release poisonous compounds and make cyanide that end up in the cow's milk. The cyanide is created while it's digested. We've got indigestible sugars from sweet potatoes, which are apparently a fairly common part of cow diets

and can lead to an overabundance of your gut microbiome. Is that right? Yes, exactly. And lead to malnutrition and even death. Yes. And then white snake root, which has a toxin that makes it potentially deadly. Why do cows eat sweet potatoes, Sam?

It's more expensive to feed them good stuff. So sweet potatoes are kind of just like, here cow, you need some calories. It's just like what's around, like the extra sweet potatoes, the bad ones that they don't want to take to the store. Yeah, yeah, yeah. Okay.

Would it be just as bad if they ate regular potatoes? Do we specifically, I guess I don't know enough about United States agriculture. Are we making too many sweet potatoes? Do people not like sweet potatoes here? I would guess people don't like sweet potatoes as much as they like a regular potato. I think that's true. This has always been weird to me because I enjoy a sweet potato more than I enjoy a potato,

but I want to eat potatoes more than I want to eat sweet potatoes. You don't always want sweet and a potato pairs better with more things. It's true, yeah. That's true. Also, you mostly get like fries from regular potatoes. And I feel like those are just like chemically engineered to make you addicted. I love me that ketchupy fry.

And also like the sweet potatoes, I think they have a problem where there's like, they grow weirdly. So there's a lot of like bad sweet, so there's a lot of bad sweet potatoes. There's a lot of sweet potatoes that don't sort of fit the grocery store desired potato shape. Give them to cows. But that has nothing to do with whether Sam's fact is true. No.

I accept that it's possible for a potato to need to eat a cow, but I don't accept that that means that. Excuse me. I guess if there was a dead cow underground, it could eat the cow. Yeah. Yeah. That's, yeah, that's how it's called. The circle of life.

It's the circle of life. That's beautiful. We've got some beef-fed potatoes over here. We've got two plants here, just grasses generally, and certain species can convert to being toxic inside of the cow, is the first

fact, whereas the third fact is snake root itself seems to be toxic and can contaminate the milk that way. I like that it's called snake root because that sounds like it's dangerous. It's also White Snake Root, like White Snake,

the most dangerous band in rock and roll history. I'm going to go with White Snake Root. I don't really have anything to base it on. It's too wibbly for me. Doesn't matter, though, because I'm not going to win.

I'm going to go with Sweet Potatoes because the grass and stuff is just, they're too close together. But that means probably that one of them is true. I'm going to go with sweet potatoes because the grasses stuff is just, they're too close together, but that means probably that one of them is true. I'm going to stop overthinking it. I'm probably wrong,

but sweet potatoes. I, the sweet potato one is the only one that I think is fake. Oh, I'd be cheating the game then. Because I don't. Two of them are definitely fake. Well,

yeah, two of them are definitely fake, but the sweet potato one is the only one that I feel like I have any sense of. Because sweet potatoes, I feel like we're really good at digesting sugars. I'll go with the snake root also. Go to twitter.com slash SciShowTangents and vote on the thing that you think is the true fact. Right. Did you vote yet?

Here it goes. The right answer is snake root. White snake root. Points occurred. Snake root milk contamination is real, and it's called milk sickness when people drink the tainted milk. And it apparently killed thousands of people on Pioneer Days, including, according to some accounts, Abraham Lincoln's mother.

Symptoms include weakness, nausea, nausea vomiting constipation and death within two days so it's like pretty nasty stuff and it happens mostly in places where people are drinking the milk from a single cow so it was almost unheard of in bigger cities and it mostly occurred on homesteads and small frontier towns and because of that no there were like no doctors out there to study what was going on and it was just just like, wow, people sure do die sometimes, I guess. And basically, that's what it was. People just chalked it up to insects or tainted water or other frontier hazards because people were just dropping dead for no reason.

So in 1809, that was the first published account of it. But it took until 1906 for the plant to be identified because nobody was on the case. And then that information spread so ranchers can watch out for it now. The toxin isn't destroyed in pasteurization. So I guess watch what your cows are eating because if you're only drinking milk out of one cow and you live in the Midwest or Eastern Seaboard, they could be poison death cows.

When you buy a gallon of milk, does that contain the milk of many cows i believe that it does i think it does yeah okay yeah this is also true of like hamburger meat well that's that's what they say about ground beef but i feel like if you if you get your ground beef from uh you know it depends on how you get it that's right a local shop milk all comes into a big a big vat and then the vat is then done like all the chemistry is done on it to make the different kinds of milks. So number one, the cyanide cow cud thing. Cud chewing doesn't really have anything to do with it, but there are certain grasses that produce cyanogenic glycosides, which I think basically is like cyanide locked up in sugar, something like that. And usually these grasses are totally safe for cows to eat. But if the grass is planted somewhere that experiences severe drought

and heat often enough, the compounds can break down in the grass and it releases the cyanide. And whether or not this can end up in the milk doesn't really matter because cows grazing on grass like this can die within a few hours of grazing. You don't milk a dead cow. That's one of the rules. Probably one of the first rules that they thought of. And it killed like 16 cows in Texas a few years ago. So it just happens every now and then, I think. Do you just like dig up all the grass and you're like, let's just torch the land and dig it up?

I should have looked into that more. I don't know i think you just be more careful about what grass is you're planting and i think that was the problem with the texas the texas thing was it was mixed incorrectly and there was the kind of grass that wasn't drought tolerant i'm pretty sure so probably you gotta just start all over again then the indigestible sweet potato sugars is based on human milk oligosaccharides. Is that how you say it? Sure.

Oligosaccharides. Yeah, yeah. Which is a sugar in human breast milk that humans can't digest, but it's thought to feed and bolster the gut microbiome of infants. And it's in human milk. Mm-hmm. I guess that's called breast milk. Human milk is a little weird to say. It is.

It's kind of strange because it sounds like you're buying it at the store. Like a cow's buying it at the store. And it's like, if you have the humans eat the wrong kind of grass, they just die. Yeah. Yeah. Which is probably very much more true for humans than it is for cows. Probably a lot more stuff we can eat that will kill us. Yeah.

Next up, we're going to take a short break. Then it'll be time for the Fact Off. Welcome back, everybody. Sandbook Totals, very easy to convey to you because it's a tie game with everyone at one, which means it's a race between me and Stefan for who's going to win this episode of SciShow Tangents because we're about ready to do the fact off.

Stefan and I have each brought science facts to present to the others in an attempt to blow their minds. And whichever fact blows your mind more, the presentee gets to give a Sam Buck too. So we're going to do this thing and we're going to decide who goes first with a trivia question that will be read to me by someone. In what year did milk start being sold in plastic coated paper cartons? Plastic-coated paper cartons. Oh.

I'm going to say 1943. 1962. Ooh, big gap there. Hank wins. The answer is 1932. Whoa. Wow. Gosh, we had plastic back then?

When did plastic start? Jeez. We had some crummy plastics before we had like cool plastic secondhand. Right, right. Bakelite was 1907.

Oh, wow. Everybody thinks that those things are just cardboard and that they're not, they're like, look, there's no plastic. And I'm like, it's

still plastic. Do you think that just paper can hold milk? In what universe would you think, oh, I'll just pour milk into this cardboard box and that will work?

This is also true, by the way, of aluminum cans. They are also lined with plastic. So you're still drinking out of plastic when you're drinking out of aluminum cans as well. I didn't know that. It's all, everything is plastic. Anyway, I guess that means I'm going to go first. So I want to tell you about a wallaby

and you want to hear about a wallaby but first i'm going to tell you a little bit about milk so there's there's usually two kinds of milk you get colostrum right when the baby is born and this is the case in in most mammals and then after that the milk composition is static so a cow's milk might vary between species but like the individual produces 3% to 4% fat, 3.5% protein, 5% lactose. Humans make 3% to 5% fat, 1% protein, 7% carbohydrate. And it's that way the whole time that that animal is making milk. It doesn't shift. But there is a group of mammals that does this differently, marsupials, and it's best exemplified by the tamar wallaby, which has a very short pregnancy. So it's only pregnant for 28 days, and then the baby is born, and it's very, very

underdeveloped and dependent on the mom. And it's basically attached directly to the mother's teat and does not let go. So to compensate for that short gestation, the wallaby babies go through a very long lactation period. It can last for up to 350 days. And during that long lactation period, the baby wallaby's nutritional needs change. So the mother changes its milk accordingly. And this is weird already, but it's going to get weirder.

So while nursing in the pouch, the wallaby mother produces milk that's higher in carbohydrates and lower in protein and fat. But 200 days postpartum, the milk composition shifts to being higher in fat and protein and lower in carbs.

The wallaby will then leave the pouch at around 250 days, but can continue suckling for up to 100 more days off of that high fat and protein milk. But sometimes the mother ends up having another baby while that first baby is still drinking milk, whatever that's called, before that baby has been weaned. And that new baby needs the old kind of milk. And so internally, you have two different teats producing two different kinds of milk. It's called asynchronous concurrent lactation. And just imagine that you have walked

into a McDonald's and you get to pick whether you want root beer or dr pepper that's the situation except it's the inside it's except it's teats and it's a wallaby so the older baby can drink from the the the teeth that has the the older baby milk and the younger baby can drink from the younger baby milk yeah but does the older baby ever have a little nip of the good yeah i don't think so good like i think that mostly during this period of time the younger baby never leaves the teat oh and so it's like basically connected older baby can kick that little baby off of the teeth yeah give me it also probably isn't very much because the little baby is so little they're so little they're just like little jelly beans yeah yeah and we have no idea how they do this.

Scientists had some thoughts about how it might work, but they were wrong. And so we do not know how on earth this mammal basically lactates. It's like it's being a soda fountain and like making different milks at the same time. What the heck? Did the scientists think it had to do with the babies? Like are the babies biting the teat or releasing a chemical in some way? They thought that it had to do with the suckling patterns.

So like a little baby would suckle differently and more continuously than a big sort of, you know, basically juvenile. But they tested that to try and like stimulate the teats as if they were one or the other and try and get it to switch. But that didn't work. There's some things just beyond our,

our realm. Yeah. We will never know. No, Sam, just cause we don't know something doesn't, doesn't mean it's beyond our realm. 10 years from now,

we'll come back and do another episode on tomorrow wallabies. And I'll tell you all about how they regulate their milk because we'll know by then then we'll know that stefan what do you have for us i've got platypuses uh platypuses are weird they are mammals but they are in a unique group of mammals known as monotremes which is just platypuses and echidnas and they are egg laying and they're just weird because they look like a collection of different animals' body parts. They have duck bills and webbed feet and beaver tails and no nipples, which is important for this episode.

So because they have no nipples, some people say they sweat out their milk, but that's not really true. They don't really sweat at all. They just lay on their backs and ooze milk through their skin onto their bellies so their young can lick it up. really true. They don't really sweat at all. They just lay on their backs and ooze milk through their skin onto their bellies so their young can lick it up. With a nipple, the milk goes straight into the baby's mouth. But here, the milk is getting exposed to the environment. And so you've

got dirt and bacteria, all kinds of things that could make the babies more susceptible to infection. But luckily, platypus milk is extra antimicrobial. So I think all milks have some antimicrobial properties in them, but monotremes have a couple extras that are unique to that group of animals. And one of these proteins is MLP, monotreme lactation protein, and it occurs in an unusually high concentration for an antimicrobial protein in their milk. And in 2018, teams at CSIRO, which is the Australian National Science Agency, and Deakin University, which is also in Australia,

they were able to replicate MLP, this protein, in a lab and then figure out the structure of the protein. And it turned out to be sort of a novel, never seen before structure. So it seems like the protein is made up mostly of alpha helices, which is this like spiral structure that's very common across all kinds of proteins. But this protein specifically, because it's mostly these helices, it's just like this mass of like spirals and it reminded them of shirley temple's hair so they called the structure shirley temple scientists are so weird i say that like knowing that i'm

vaguely a scientist but shirley temple protein so like the structure of proteins in general influences how each protein behaves and they don't know exactly how that structure interacts with bacteria, but they know it is more antimicrobial. And they're interested in seeing how that structure could be used to fight antibiotic resistance, basically, because that's becoming a bigger and bigger problem over time. And as antibiotics are becoming less effective, we have to keep exploring all these different options. So they're like, okay, this is unique protein. It's got a weird structure that we don't know of. Can we recreate this and create different

medications that could fight antibiotic-resistant bacteria? They did note, though, that since proteins break down when you ingest them, they don't think you could make an oral treatment with this, but probably like an ointment or a wound dressing or something that could be more effective. They were in 2018 looking for collaborators to take this research to the next level. So if that's you,

it's time to save the world, buddy. I have a question about what happens to the extra milk. Do the babies just like lick the milk belly until there's no more? Or at some point, does the platypus mom have to be like, I got things to do, and then flips over and gets rid of some milk? That's a good question. I don't know.

Well, they swim a lot, so I imagine whatever is left over washes off. Milk belly. Look, there's probably a lot that's stinky about a platypus life. Yeah. Yeah, I guess so. You are choosing between two facts. We've got Tamar wallabies who can change their milk continuously as a baby wallaby

develops and produce different kinds simultaneously for two differently aged babies. Or, from Stefan, platypus milk contains a unique antimicrobial protein that could unlock new ways to fight antibiotic-resistant bacteria. You guys ready?

Three, two, one. Hank. Hey, I'm cleaning up today. I'm back, I'm back. Now it is time to ask the science couch where we've got a listener question for our virtual couch of finely honed scientific minds. This week from Krebshouting, who asks,

why is milk mostly uniform in color no matter the animal it comes from? And I assume that this is because milk is an emulsion of little fat droplets and that's what it looks like when you do that, right? Yeah, you're enough of a chemist to guess at an answer. Do you wanna explain what an emulsion is in chemistry? Yeah, so like milk has fat dissolved in it,

but we all know what happens when you put fat in water. Like they don't mix together. Oil and water don't mix. That's like a metaphor, it's so true. But if you can create chemical ways to get tiny droplets of fat to have little things around them that basically keep that droplet dissolved in water so that it doesn't separate out or doesn't separate out easily. And that is an emulsion. It's when two substances that normally would not dissolve in each other,

dissolve in each other somehow. I think, basically. I'm 40. I haven't been a chemist in a long time. Yeah, that's basically it. So there are in milk, which is like water is the main liquid in it. There are fat globules and protein globules. And when milk is homogenized then it's gone through like extra processing to make it like a smooth milky color instead of like i think if you get milk more freshly or less processed from farms it can separate into like cream on top and that's because it's like less of an emulsion and the fat particles are what are key here because they're so much bigger than the protein particles so just like the way color works is light is made up of a spectrum and so light hits an object and then what gets reflected back into our eyes is the color we see

and so like off of most plant leaves only the color green is reflected back into our eyes is the color we see. And so like off of most plant leaves, only the color green is reflected back into our eyes because of chloroplasts. And the fat molecules reflect back all wavelengths of light into our eyes. So that's why it appears white to us. So thank the fat. If you want to ask the science couch your question, follow us on Twitter at Slideshow Tangents, where we'll tweet out topics for upcoming episodes every week. Thank you to at TangentialOtter at HeyLets and everybody else who tweeted us your questions this week.

Sandbuck final scores for once! I win! Three points to everybody else's one, which makes it so that I am only five points behind. You're in striking distance. I just need to do that a bunch of times. If you like this show and you want to help us out,

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I've been Hank Green. I've been Sari Reilly. I've been Stefan Chin. us I've been Hank Green I've been Sari Riley I've been Stefan Chin and I've been Sam Schultz SciShow Tangents is a co-production of Complexly and the wonderful team

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The selenodon is a shrew-like venomous mammal that's only on the islands of Cuba and Hispaniola. They are mammals, so they produce milk, but babies have to drink it from teats near their mom's butt butt teats so they got butt teats and the ecologist joe nunez mino described it as quote the teats are sort of in the armpit of the rear legs and sometimes the females will kind of run around dragging the babies these animals gotta get their shit together. They don't look right. Yeah, they do look a little upsetting.

They are weird. They diverged like 76 million years ago from other mammals and trees. So it's like they are a weird evolutionary offshoot. They're one of the only venomous mammals. And so the butt teats are actually pretty low on the number of weird things about them. Yeah.