This is a transcript of the Gastropod episode From Fountain of Youth to Fruit on the Bottom: How Yoghurt Finally Made it Big in America, first released on November 18, 2025. It is provided as a courtesy and may contain errors.

PRIYA KRISHNA: Yogurt is a, is a miracle. It’s like the creamy result of when you leave milk out for too long and, and zhuzh it up a little bit. I think yoghurt is like one of the dreamiest substances we have to eat in existence.

NICOLA TWILLEY: I mean, I like yoghurt fine, but we live in a world with chocolate. Still, I’m definitely not here to diss it: yoghurt is an extremely popular substance and rightly so.

CYNTHIA GRABER: There’s fruity yoghurt, plain yoghurt, greek yoghurt, drinkable yoghurt, Icelandic yoghurt, frozen yoghurt, the list goes on and on. So who invented this dreamy, infinitely versatile food? Where did it come from?

TWILLEY: Fortunately, Cynthia, you are in an episode of Gastropod, the podcast that loves to get to the bottom of exactly these kinds of questions. So let’s have a look at yoghurt through the lens of science and history! I am, of course, Nicola Twilley.

GRABER: And I’m Cynthia Graber. And if you happen to catch any ads for yoghurt, it seems like it’ll solve all of your health woes. Where did that come from, how did this idea start that it’s like this elixir that will bestow immortality?

TWILLEY: The other thing, is like you said, there’s a million different kinds, the yoghurt aisle stretches half the length of the store. But what’s the difference between all the different yoghurts, like Greek or Australian or Icelandic or even your basic Dannon or Yoplait?

GRABER: All this, plus yoghurt made with the help of some friendly ants. Yes, ants, the insect kind! This episode was supported in part by the Alfred P. Sloan Foundation for the Public Understanding of science, technology, and economics and by the Burroughs Wellcome Fund for our coverage of biomedical research. Gastropod is part of the Vox Media Podcast Network, in partnership with Eater.

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KRISHNA: So my father learned to make yoghurt from my grandmother, my maternal grandmother. And he started making it in the ‘90s. And he has perpetuated the same yoghurt starter since then.

TWILLEY: This is Priya Krishna, a cookbook author and food reporter at The New York Times. And, of course, a mega-yoghurt fan.

GRABER: Yoghurt was a foundational part of Priya’s childhood.

KRISHNA: Every week, my dad would stand over the stove stirring hot milk, pouring it into a container. He made one large tub of it in a stainless steel container, and then he invented what my sister called personals, which were like smaller individual size servings of yoghurt. And… this was what we ate. Not a day went by that we didn’t have yoghurt.

TWILLEY: Most of us buy our yoghurt at the store these days, but it’s not hard to make at home. You just have to warm your milk, and then add a little bit of your previous batch of yoghurt.

GRABER: Because that bit of yoghurt has all the live microbes you need to make yoghurt, and they’ll get right to work and start turning the warmed milk into a new batch. This is just what Priya’s dad did, week after week.

KRISHNA: And I think like the, the biggest panics that would happen in our house were when we were low on yoghurt or where all that was left was sort of the watery curds at the bottom of the pot. But he would keep these sort of “break glass in case of emergency” containers of yoghurt in the freezer. Just in case one of us ate all of the yoghurt and there was like nary a, a tidbit to start the next batch with. And so he had all of these contingency plans if there was not starter to do the next batch.

TWILLEY: This level of preparedness was essential because Priya’s dad’s yoghurt was extremely delicious.

KRISHNA: My dad’s yoghurt—it’s sort of an Indian style yoghurt, which means it’s creamy, but it’s also very, very tart. And, just the way it came out in these really wonderful chunks that defined my dad’s yoghurt.

TWILLEY: Like I said, delicious. And also legendary.

KRISHNA: My dad will distribute his yoghurt starter to friends. So if someone asks him nicely, he will bring some. Because there’s this idea that, you know, the, my dad’s yoghurt starter can make like really pristine yoghurt.

GRABER: And all those families were so excited about this gift of a yoghurt starter because yoghurt wasn’t just a snack, it was really an important everyday food.

KRISHNA: My mom used it to make raita.

GRABER: Raita is a yoghurt sauce that’s served almost every meal in Indian cuisine.

KRISHNA: She would also strain it and use it to make hhrikhand, which is like this very thick, cardamom yoghurt, dessert. It’s like one of my favorite desserts of all time. And among many South Asian families, I know yoghurt is essential. It is often not something you buy, it is something you make. It is sort of, an underpinning to our meals. You serve yoghurt with an Indian meal, it like sort of cools you off. It functions as sort of a refreshing counterbalance to this food that has—often has a lot of spice. I don’t mean heat spice, but just like a lot of spices in general.

TWILLEY: Recently, Priya reported a story on the importance of homemade yoghurt among South Asian families, and how carefully each family’s yoghurt starter is preserved.

KRISHNA: And the stories I heard were so endearing. It was like, people hiding yoghurt starter in their suitcase when they were coming from India. Or this one woman told this story about moving cross country, and holding her family’s turtle in her lap and having the yoghurt starter, next to her, strapped with a seatbelt. Like in a seat. Like the yoghurt got its own seat in the car. And that’s how important it is to perpetuate the yoghurt starter.

GRABER: But South Asians aren’t alone in their love for yoghurt. Today it’s popular around the world. And it’s been popular for thousands of years.

TWILLEY: Basically for as long as we’ve had milk, and containers to put it in, which is something like 9 or 10,000 years.

VERONICA SINOTTE: So how long have we been eating yoghurt? Probably since we domesticated animals to produce milk.

GRABER: Veronica Sinotte is a professor of food science at the University of Copenhagen. And it seems like the discovery of yoghurt was a perfect marriage of domesticated animals, the invention of pottery to hold liquid, and of course place.

TWILLEY: There’s a popular story that the big yoghurt breakthrough came when some nomadic tribesperson in central Asia was carrying some milk in an animal skin pouch, and by the end of a long hot day on horseback, the milk had turned into sour curds. AKA the very first yoghurt.

GRABER: That’s a fun and picturesque story. But most researchers think that isn’t how the discovery came about. They think it’s more likely that milk was left in a ceramic container outside in the warm sun and microbes just started doing their thing. No jiggling on a horse required.

JUNE HERSH: Because all you really need in order to create yoghurt is you need a milk source, and you need bacteria, and you need the right climate. And so you now had those three things coming together in a very organic way.

TWILLEY: This is June Hersh, she’s a cookbook writer and the author of Yoghurt: A Global History.

HERSH: You had them take this milk product, they put it outside. They were in the area near Turkey, so it was hot. And they left it out there. And it curdled. And it thickened. And it coagulated. The Turkish word yoğurmak, which means to coagulate or to thicken, is really descriptive of what the product was that they got.

TWILLEY: Typically, if you think of leaving milk out on a hot day, you think of it going bad and maybe even making you sick. But this coagulated sourness was not only tasty but also maybe made people feel better.

GRABER: One theory about why people latched on to this new tangy, thickened milk that didn’t make them sick has to do with my personal plague, lactose intolerance. Most people at the time in those regions couldn’t tolerate lactose and something like 70 percent of all people around the world still can’t today. Lactose is a particular milk sugar that we humans can digest as babies, it’s why we can thrive on breast milk, but most people lose that tolerance as they age.

TWILLEY: Milk is super nutritious, it seemed like it could have been a great food resource, but drinking more than just a tiny bit was and is a fast-track to digestive distress for most adults. But these early people in what’s now Turkey found they could have a little bit more of this soured, thickened version of milk without wanting to puke—and that’s because there’s about half the lactose in yoghurt that there is in milk.

GRABER: And that’s because that lactose, that milk sugar, is a great food for—yes, microbes! And now you can drink! Because the trick to turning milk into yoghurt is really microbes.

SINOTTE: And the microbes in it, often bacteria produce acids and transform that milk through their microbial metabolism into a tangy yoghurt.

TWILLEY: These are not just any old microbes. They are two very specific lactose consuming microbes

SINOTTE: Yoghurt by definition contains Streptococcus thermophilic, and Lactobacillus delbrueckii bulgaricus.

GRABER: And these microbes do one other important thing, other than consuming lactose. As Veronica said, they produce acids, and those acids, that acidic taste in the yoghurt, it keeps out other microbes that could be toxic to humans. Those are the ones that would just turn milk bad. Getting a hold of those particular acidic microbes was really helpful in the days long before refrigeration.

SINOTTE: As you start to milk animals, or maybe have a herd of animals, you might not be able to consume all the milk in one period of time, right? So how are you gonna preserve this lovely, nutritious resource? Fermentation, that microbial transformation allows for you to preserve it. So you could turn milk into something like yoghurt. And that prevents other microbial spoilage organisms from getting in there, essentially preventing your food from rotting or going bad. So that could be a major advantage.

TWILLEY: This is truly a microbial blessing. These two microbes made milk both longer lasting and more digestible. No wonder people are protective of their starter cultures.

GRABER: But so where did these incredibly useful microbes first come from?

TWILLEY: This is the trillion dollar question. No one really knows, because these two microbes can be found in all sorts of places in the wild—from human saliva, to animal guts, to wildflowers and grasses.

SINOTTE: Some people suggest that the microbes in our yoghurt that we use today come from animals. They like to live at really warm temperatures, more like mammalian body temperature. The question becomes, did it come from the cows or the animals themselves, and it was part of their microbiome that kind of transitioned into our fermented foods? Or is it part of our microbiome in these lovely warm environments like our mouth or other places?

GRABER: We may never know exactly where these two main yoghurt bacteria originally came from. But there’s another twist in the yoghurt origin story, and it’s that yoghurt wasn’t one thing, it was plural: yoghurts. And each one might have had a slightly different microbial community that was fermenting it.

SINOTTE: Traditional yoghurt can have many different types of lactic acid bacteria. Microbes that are eating those sugars in the yoghurt and then producing lactic acid. That could be these two traditional yoghurt microbes, but it could be a variety of other species. They also might contain some yeasts. That might add a little bit of effervescence or different flavor profiles.

GRABER: All those different microbes and fungi could have really come from anywhere, it’s kind of a tantalizing mystery. Veronica studies the ecology and evolution of microbes in fermented foods, and she was curious about the origin of these microbial communities in yoghurt.

TWILLEY: What really intrigued her were stories from her colleague Sevgi Mutlu Sirakova, who’s originally from Bulgaria. Sevgi told Veronica about yoghurt that was created by putting ants in it. Which made Veronica wonder: could the microbes in this yoghurt have come from ants?

SINOTTE: Sevgi had collected stories of ant yoghurt that came from Turkey. It came from Bulgaria. We’ve also collected other stories that come from other Balkan countries.

GRABER: So she and her colleagues traveled to a town in Bulgaria, where Sevgi’s family is from. And they worked with the community to recreate that traditional ant yoghurt so they could study it.

SINOTTE: They hadn’t actually been making ant yoghurt, it seemed like, regularly or potentially even for decades. But many people had living memories of how it was made.

TWILLEY: Ant yoghurt turns out to be a seasonal treat.

SINOTTE: This ant yoghurt is made as part of a springtime tradition or a spring celebration, religious celebration, called the Hiltrelas. And as spring sets in, everything starts moving and growing. And so do the ants. Their colonies become alive again. They start crawling all over their nest, but also all over the environment.

GRABER: From the stories people told Veronica and her colleagues, it seems like people would drop whole ants into warm milk and then bury the container of that milk in the ant colony overnight. But why? Why ants, why the one particular kind of ants that they used?

SINOTTE: So why these ones? These ants produce acid. They produce formic acid. If you disturb them, they’ll even start spraying it at you and you can smell it. If you decide to lick your hand, you would certainly taste it, that it’s a bit lemony.

TWILLEY: Adding an acid to milk—something like lemon juice—is a known trick to kickstart the fermentation process, whether you’re making yoghurt or cheese. You don’t need it, but it helps create the nice acidic environment that the microbes like to work in.

SINOTTE: And I think that might be one of the reasons why they started to think, oh, these are a sign of spring. These ants are acidic. Maybe acidic like the yoghurt. Could that be important? The ant colony is also warm. So if you were to put your hand inside the ant colony, it’s like this nice, cozy environment. Much like that nice, cozy, warm environment that you would wrap your yoghurt in, wrap that blanket around it so it stays warm. So it could be something like an incubator. Those are maybe some of the reasons why they chose ants and particularly those ants because certainly not all ants will work for this fermentation.

GRABER: The story of ant yoghurt is an interesting bit of cultural history, but Veronica’s a scientist, she wanted to understand exactly what was going on, what the ants were contributing to the yoghurt-making process.

TWILLEY: And to do that, she had to make ant yoghurt back at her lab, in Denmark.

SINOTTE: So the ants are in many different places actually. And luckily they were in our own backyard, here in Copenhagen. They’re a major fixture of the landscape in these pine forests. So it was really easy. We collected the ants from the Danish landscape, brought them back to the lab.

GRABER: They actually crushed the ants so they could release anything and everything that was in the ants into the milk. The milk itself was totally sterilized.

SINOTTE: It was this really controlled test of: can the microbes and the things in the ants get into the milk, and how does that work in that yoghurt making process, on really this food science level?

TWILLEY: Veronica and her colleagues left the milk with the ants to incubate overnight. And when they came back, it was definitely well on its way to yoghurt-ification.

GRABER: It had begun to coagulate, it was a little acidic, it wasn’t fully yoghurt, but it was getting there. And so they then analyzed the ants themselves and the yoghurt, to find out what was in that yoghurt that hadn’t been in the sterilized milk.

TWILLEY: Obviously, the ants had brought acid—that lemony formic acid they’re known for. But they’d also brought the all important microbes.

SINOTTE: The ants bring in lactic acid bacteria. They brought in this really cool bacteria called Fructilactobacillus sanfranciscensis, which actually is normally found in sourdough bread. The ants also brought in acetic acid bacteria that they seem to keep in their mouths and in their guts, and have evolved with for millions of years, likely.

GRABER: Veronica was excited to find out that these ants contributed just what was necessary to make yoghurt! But it turns out that the ants had another trick up their sleeves, another contribution to the yoghurt-making process: they dropped off some enzymes, too.

SINOTTE: These enzymes munch on the proteins, break down these proteins into smaller peptides or amino acids, and that’s great because the food’s more nutritious. But also the other microbes in the microbial mix can use those amino acids for their own metabolism and growth. Enzymes can also contribute to the texture of yoghurt. So enzymes can cause the casein, this major protein molecule in yoghurt. It causes the molecules to aggregate a certain way. And then the milk coagulates.

TWILLEY: In other words ants are basically an all star yoghurt making machine!

GRABER: Of course, you don’t need all those ingredients to make yoghurt, and you don’t *need* ants in particular. In fact as Veronica said, most people they spoke with in Bulgaria aren’t even making ant yoghurt anymore.

SINOTTE: So when other researchers have gone out and sampled all household yoghurts around Bulgaria, for example, they don’t find any ant microbes in them.

TWILLEY: So ants are probably not the origin of today’s yoghurt bacteria. But Veronica does wonder whether the sourdough bacteria she found in her ant yoghurt—whether that might have made its way from ant yoghurt into the sourdough starters behind the bread we still enjoy today.

SINOTTE: It’s not unheard of to use yoghurt in your sourdough starter. But the moral of the story is that the yoghurt could be used in different fermentation products, like sourdough. It could be in the kitchen environment.

GRABER: And this isn’t the only story of insects helping create delicious foods by bringing along the necessary microbes. There’s been research in Italy, for instance, showing that some of the microbes that can turn grape juice into wine came from wasps.

TWILLEY: And so while, again, no one is saying that ants are the forefathers of all yoghurt, what’s so cool about the fact that ant yoghurt actually works is that it helps show how many different ways humans could have arrived at tangy, fermented dairy products. Today, we mostly just rely on two microbes, but imagine the variety in the past!

GRABER: I still really want a time machine, anyone out there help me out? But Veronica and June have some ideas about what that variety might have tasted like.

SINOTTE: So there was no single yoghurt with a specific flavor. I think it was inevitably more complex than the yoghurt you can buy at the grocery store today, in its acidity and other different profiles. Maybe it had some botanical notes to it. It depends on who was making it and how, just how they did it and what microbes they carried with them and carried with their yoghurt.

HERSH: So depending on the strain of bacteria that you use, you get a very different taste.

TWILLEY: Until someone comes through with Cynthia’s time machine, that’s as close as we’ll get to an ancient yoghurt flavor profile, or profiles. But what we do know is that ancient people loved it. It was a hit and it caught on all over, throughout the Balkans, the Middle East, the Caucasus, and Central and South Asia.

GRABER: Yoghurt was mentioned in lots of ancient texts in lots of different languages. And it was also almost always mentioned as something that was particularly healthy, almost medicinal.

TWILLEY: The classic “yoghurt as the key to health” story may or may not be true, but it is a good one. It stars yoghurt, obviously, but also King Francis I, who ruled the yoghurt-free nation of France in the early 1500s.

HERSH: From what the stories go, he had a sour stomach and an even more sour disposition. And all of the people in his court wanted somehow to get this man some relief, feeling that [LAUGH] if they could relieve his indigestion, perhaps he would not be such a, a disgruntled ruler. And so he reached out to Suleman the Magnificent in the Ottoman Empire. And he said, we hear you have a doctor who can cure sour stomach.

GRABER: That doctor was a Jewish guy who, apparently, so the story goes, he hiked all across continental Europe from the Ottoman Empire to France with a herd of sheep. Got there, and made some yoghurt with that sheep’s milk.

HERSH: He supposedly cured the sour stomach and the chronic indigestion of the French king. Forever stayed in their good graces. Improved the health and the wellbeing, apparently, of everyone in France, because now supposedly, he became this lovely, benevolent ruler. Because his stomach wasn’t disagreeing with him.

TWILLEY: At the time, Francis proclaimed yoghurt the elixir of life—which you would think would help it catch on in France. But it did not. It took many more centuries and a bunch of starfish before yoghurt would make it big in the West. That story, coming up after this word from our sponsors.

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GRABER: We’ve said that yoghurt got big in a pretty significant swath of the world, from the Middle East all the way through Central and South Asia. But it wasn’t particularly well-known in most of Europe—that’s why King Francis didn’t think of taking yoghurt to cure his stomach without some outside intervention.

TWILLEY: In some parts of the world, it makes sense that yoghurt didn’t get invented. There weren’t many milkable animals in North and South America, Australia, and the Far East. But Northern and Western Europeans had milk up the wazoo. And that milk would have spoiled without refrigeration, too—maybe a little bit more slowly than in the heat of Turkey, but still. So why didn’t they invent yoghurt?

GRABER: It turns out that the climate is key. The particular microbes that make yoghurt yoghurt—yoghurt isn’t cheese, it’s not sour cream, it’s not buttermilk—these yoghurt microbes not only love heat, they can’t live without it.

TWILLEY: They just were never going to be happy in England or Sweden or even France. So those places developed a completely different coagulated milk culture. So you get butter and aged cheese, they need cool temperatures which meant they weren’t great options in the Middle East or Central Asia.

GRABER: Northern and Western Europe all also did have their own versions of soured milk, milk that’s been lightly fermented and curdled. But these were made with different microbes that like the cooler temps in northern Europe, and the resulting soured milk is a lot less sour than yoghurt is—they have a kind of fresher, milder taste. These are like British and Irish clabber, creme fraiche in France, German quark.

TWILLEY: Those milder, lower temperature microbes also, incidentally, eat a lot less of the lactose, the sugar in milk. Which may have contributed to making it an evolutionary advantage for Western and Northern Europeans to pass on the mutation that makes them able to digest lactose as adults.

GRABER: But the point is that for Western Europeans, yoghurt just wasn’t a food they were familiar with. If they did get a taste, it would have been something super exotic, like the yoghurt that the Jewish doctor from the Ottoman Empire had to make for the French king.

TWILLEY: But even more importantly, no one was familiar with what on Earth was making any of these fermented foods. Despite eating them by the boatload, no one had seen a microbe until microscopes were invented in the 1600s, and no one knew what they did till Louis Pasteur came along in the 1800s.

GRABER: Pasteur may have figured out microbes caused fermentation, but he didn’t do research on yoghurt. He did end up creating the Pasteur Institute in France to study diseases and microbes, and the first foreign scientist he invited to come work with him was named Elie Metchnikoff.

LUBA VIKHANSKI: He was a Russian biologist who spent the second half of his time in France. He worked in Paris at the Pasteur Institute. And, he was very famous, not just as a scientist, but he was—at the beginning of the 20th century he was one of the most famous people in the world.

GRABER: Luba Vikhanski is a science writer and author of the book Immunity: How Elie Metchnikoff changed the course of modern medicine.

TWILLEY: Metchnikoff is a big deal in the story of yoghurt, he’s sometimes known as the grandfather of yoghurt. But his scientific reputation was not built on dairy products. He won a Nobel Prize for basically wholesale coming with the idea of the immune system.

VIKHANSKI: It wasn’t called that at the time. But, he developed the very first modern theory of immunity. Until then, there, there was no notion of immunity in the way we know it exists today.

GRABER: In the lab in the late 1800s, Metchnikoff was studying starfish larvae. They’re transparent, which makes them easier to study. He noticed that there were cells that were basically digestion cells, they ate food for nourishment. And somehow, he had the idea that maybe they don’t just eat food. Maybe they eat harmful things too as a form of protection.

VIKHANSKI: And he performed one of the most famous experiments in the history of science. He introduced into this tiny larvae, little pieces of thorns from a rose bush. And then he saw the next day that indeed, the cells had ganged up on these thorns to protect, you know, the little animal.

GRABER: They seemed to be a built-in defense system, an immune system. Metchnikoff continued his experiments and eventually discovered that there’s a similar, more sophisticated system in humans made of white blood cells that surround and ingest harmful foreign particles.

TWILLEY: This was an amazing breakthrough—it was so ahead of its time it was ridiculed at first. But ultimately it made Metchnikoff famous. And so he got an invitation to come work at the center of the universe for science at the time, the Pasteur institute in Paris.

GRABER: This was an incredibly exciting time in science and particularly for the Pasteur institute. Pasteur had just created a vaccine against rabies in 1885.

VIKHANSKI: And that was like a miracle cure. This was just something that was—totally captured people’s minds. And everybody thought that this was like the beginning, which indeed it was, a new era in medicine.

TWILLEY: Metchnikoff carried on researching the immune system at the Institute. But, as tends to happen, he was also aging. He was in his 40s when he arrived in Paris, but by the time he got into his 50s, he was beginning to feel like… well not a spring chicken anymore.

VIKHANSKI: He started to worry about getting old. That was then, I guess, you know, considered old and [LAUGH] that’s how he felt.

GRABER: Metchnikoff had an idea at the time—this wasn’t just his theory, it was kind of a popular theory in medicine—

VIKHANSKI: It was even, I would say, verging on a medical obsession. It was, it was called auto intoxication.

TWILLEY: The idea was that germs, microbes in your intestines, were causing you to rot from the inside out. And Metchnikoff figured that was probably what was causing aging.

VIKHANSKI: So he came up with the idea that aging is a disease. That it’s a disease that’s called by harmful infectious organisms in the gut. And it, it should be cured, like any other disease. That was his starting point.

GRABER: This belief, this theory, it made him a total germaphobe. He tried every way possible to prevent what he saw as harmful microbes from getting into his intestines.

VIKHANSKI: He had a burner in the lab and he, sterilized everything. He boiled even bananas because he thought that maybe somehow through the skin, the germs can, can get in. And when he went to restaurants there where waiters would bring, they knew him. They would bring a burner and he sterilized utensils for himself and for his guests.

TWILLEY: But just avoiding bad germs wasn’t enough. Metchnikoff wanted a cure. And just like the immune cells he’d discovered in starfish, he wondered if there might be good germs that could eat the bad ones. And that is how yoghurt entered the picture.

VIKHANSKI: Because fermented milk, from beginning of history, was known to preserve milk. Like other products rot and spoil, and milk doesn’t. I —it becomes sour. So what actually stabilizes it. It wasn’t known.

TWILLEY: Metchnikoff began to speculate that maybe the microbes that fermented the milk to turn it into yoghurt were eating the bad ones that would normally make it spoil, keeping milk fresh longer. We know today that isn’t how it works: as we said, they create an acidic environment that promotes the growth of beneficial bacteria at the expense of nastier ones. But Metchnikoff didn’t know that, and good microbes that could eat bad ones that made things rot was exactly what he was looking for.

GRABER: Metchnikoff was already familiar with yoghurt. As we said was from Russia, and people in Russia ate a lot of yoghurt, and it had been thought to be a particularly healthy food. In fact, his first wife back in Russia, she had tuberculosis, and one of the foods he and the doctors gave her to try to restore her health was yoghurt. It didn’t work, she did die, but that didn’t turn him off the food.

TWILLEY: The real breakthrough came when a Bulgarian student called Stamen Grigorov brought back some yoghurt from his home region to show his professor. They found a bacteria in it—one of the two that’s in all yoghurt today.

VIKHANSKI: And they made extraordinary amounts of lactic acid. And they, they call these bacteria Bacillus bulgaricus.

GRABER: The professor in Switzerland knew Metchnikoff, so he sent him a sample of the yoghurt and of the lactic acid bacteria. And he also passed along that in Bulgaria there were an unusual number of people who lived until they were over 100.

TWILLEY: There were actually only so many centenarians because there were so few accurate records of their dates of birth, but it made for a compelling story.

VIKHANSKI: And, for Metchnikoff, it all fitted in together perfectly. Like he was, his theory that aging, is caused by microbes in the large intestines, and that you can fight it with good bacteria. And the good bacteria, for example, there are in yoghurt, and here are these Bulgarians who are living proofs of that. They eat so much yoghurt, and look at them.

GRABER: So Metchnikoff started giving lectures where he shared his new theory about autointoxication and the power of yoghurt to cure aging.

VIKHANSKI: He was a big, populariser of, of science. And he was a very eloquent speaker and he was very passionate, and journalists loved him. He was sort of like a media person. He was probably the equivalent of, like Carl Sagan was for astronomy, and he was the same for health, you know, and medicine.

TWILLEY: So when he started talking about yoghurt, you can imagine that people listened. And then came the tipping point: a lecture that Metchnikoff gave on the subject of old age and its prevention in Paris in 1904. Luba says that is when the yoghurt frenzy really took off.

VIKHANSKI: And he brought with him an old dog and an old parrot. And the dog looked sort of shabby. And this was sort of his way of showing this is what happens when you have a large intestine full of, of germs. And birds have like, almost no large intestine. And the parrot was 70 and it looked very young, sort of, and feisty.

GRABER: These were visual props that at least to Metchnikoff proved, so to speak, the ills of toxic gut microbes. Today we know it’s useful for humans and dogs to have a large intestine. Birds don’t have the same type of large intestine because they need to save space to stay aerodynamic—they’ve evolved different digestive hacks to make up for that. But in any case, that wasn’t the only thing he lectured on that day.

VIKHANSKI: He talked about many things, but the one thing that caught on was this maybe mention of yoghurt and the Bulgarians, who live these long and healthy lives.

TWILLEY: He also said he personally ate yoghurt three times a day.

VIKHANSKI: And it was just picked up by the press without any caveats. Without a—you know, any mention that it’s a theory, that it’s just an idea basically. And journalists just ran with it.

GRABER: The headlines were splashed across papers in Europe and in America. “Sour Milk is the Elixir!” And quote, “pretty ladies and brilliant gentlemen, who don’t want to age or die, here’s the precious recipe: eat yoghurt!”

VIKHANSKI: I found, you know, clip—clippings from Chicago, from Los Angeles. From the Pasteur Institute, the great Professor Metchnikoff comes up with a cure for aging.

TWILLEY: Eating yoghurt was suddenly all the rage in Paris.

VIKHANSKI: So first of all, there were cafes that sold it like you could go for your five o’clock yoghurt. And there was like this one cafe on one of the Parisian boulevards that said, “come and eat yoghurt, and, following the work of a great professor Metchnikoff, it will prevent the disastrous old age.”

GRABER: Yoghurt was also sold in tablets, and there were chocolates that were spiked with yoghurt and yoghurt bacteria.

TWILLEY: Doctors were recommending it to their patients in extremely generous quantities.

VIKHANSKI: So the British Medical Journal, for example, wrote in the review: “yoghurt can be used for an indefinite time without harmful results, if the dose be not too large. One kilogram a day should not customarily be exceeded.”

GRABER: For American listeners, one kilo is 2.2 POUNDS of yoghurt. Per day. No thank you.

TWILLEY: That is in fact, what many Americans said about yoghurt at the time. There was one snippet from the newspaper in Elk Falls, Kansas, that I found particularly lovely. It says, quote: “Curdled milk, of a peculiar kind, made after a Bulgarian recipe and called ‘yaghurt,’ is now a Parisian fad and is believed to be a remedy against growing old. A correspondent who has tried it, says he would prefer to die young.”

GRABER: And, speaking of dying young, Metchnikoff did not in fact live forever. He had not cured aging with yoghurt.

VIKHANSKI: Metchnikoff died in 1916. And he died at the age of 71. And he thought that if you take all these preventive measures, he believed that people could and should live to 150. And when he died halfway through to that mark, you know, it was a huge disappointment for many people.

TWILLEY: Metchnikoff had been afraid this might happen.

VIKHANSKI: And he was very worried about all this harming his, his theories. And he was talking about how his whole family didn’t quite live long. And that he started very late with his healthy regimen. He made all kinds of, explanations, provided all kinds of explanations for why he wasn’t going to live till 150.

GRABER: Metchnikoff may have been a household name in his day, but his fame kind of died out in the decades after he died. That said, the research he did was totally ahead of its time.

VIKHANSKI: He conducted just absolutely modern and totally pioneering studies of the gut microbiome. And he tried to answer the question, for example, is it essential? Can we live without it? And which germs are good, which ones are bad? He found that the microbiome changes throughout a person’s life. He found that it could be changed by diet. He was a very firm believer in preventive medicine, which was—he was like a hundred years ahead of his time in, in everything. But I think in terms of his popular image, and if he is remembered for anything, it’s just for yoghurt.

TWILLEY: But even when it came to yoghurt, the Metchnikoff-inspired yoghurt fad ran out of steam in most of the world pretty quickly. In the US, yoghurt fell back off the radar almost completely. So how did we get from preferring death to eating yoghurt to entire supermarket aisles devoted to it today? That’s coming up, after this break.

[BREAK]

MATTHEW WOLF-MEYER: Adelle Davis, I have come to describe as the most popular cookbook writer you’ve never heard of. Because she sold, by all accounts, millions of dollars worth of her cookbooks over the course of the 20th century. And is not someone that I hear anybody talk about.

GRABER: Matthew Wolf-Meyer is a professor of science and technology studies at RPI and author of the book American Disgust: Racism, Microbial Medicine, and the Colony Within.

WOLF-MEYER: I got interested in her because she’s one of those people who’s like an early proponent of yoghurt. And you can see in the early cookbooks that she’s trying to convince people that it’s like an edible substance. You know, that like, maybe they’ve heard about it. But they’ve definitely never tried it.

TWILLEY: Adelle’s books combined nutrition advice with recipes, they were called upbeat but also sort of patronising things like “Let’s Eat Right” and “Let’s Have Healthy Children.” She got going in the late 1940s and hit her stride in the 1950s. And by then, most Americans had gratefully forgotten all about Elie Metchnikoff and wouldn’t know yoghurt if they bumped into it on the street.

GRABER: Adelle had very strong feelings about nutrition. A lot of her nutrition advice was pretty sound, she recommended eating whole grains and vegetables and that people cut down on meat. She was also unfortunately a big proponent of megadoses of supplements and had some not particularly science-based recommendations. She recommended large doses of vitamins that could be and sometimes were harmful for her readers and their families.

TWILLEY: She was a big yoghurt fan, in part because she was a milk fan, she thought milk was super healthy and a great alternative to meat. But she also did recognize that yoghurt had some unique microbial benefits too.

WOLF-MEYER: The thing that I often think about is like, this recommendation that she has that if you, you’re feeling ill, that you eat two cups or four cups of yoghurt, right? That it’s like—a significant amount of yoghurt in order to deal with stomach upset.

GRABER: But apart from spooning out cups when they were feeling crappy, Americans didn’t know how to regularly incorporate yoghurt into their diets.

WOLF-MEYER: And so in order to kind of convince people that it’s worth eating, she’s thinking about like, ways that you can convey its palatability. And part of that is including it in recipes, but some of it is just convincing people that it counts as food. And she’s there to kind of bridge the gap conceptually. To like convince you, it can be eaten and give you some ideas about how it can be eaten.

TWILLEY: Adelle not only provided a recipe for making yoghurt at home, she also had a recipe for a yoghurt sauce with grated onion, mustard powder, and Worcestershire sauce to serve with cold cuts. And another one to go with cheese cutlets.

GRABER: Neither sound particularly pleasant, to be honest, but Adelle’s story highlights two main points about most of America at the time—okay, maybe more than two, because first food sounds pretty terrible back then. But also, most Americans were one, not familiar with yoghurt and two didn’t really have easy access to it.

WOLF-MEYER: Even Davis when she’s talking about like, where would you find yoghurt? She’s recommending people go to their, you know, nearby European grocery stores. That it’s not gonna be something that you’re, you’ll find at a mainstream grocery store.

TWILLEY: At the time, yoghurt was definitely something you’d only find at the quote unquote “ethnic” food store. It was something that Greek or Armenian or Eastern European immigrants would make and sell to their own community.

GRABER: One of those immigrant families, they were Armenians who came to the US in the early 1900s and they moved to Massachusetts.

WOLF-MEYER: It starts with Sarkis and Rose. Who are the father and mother of this family. And they start a intensely local yoghurt distribution network.,

TWILLEY: Rose literally made the yoghurt at home, on the stove, the way she and her family always had.

WOLF-MEYER: In the beginning, it’s just plain yoghurt, right? And they tell the story that Rose brought the bacillus to start the yoghurt from Turkey when she immigrated.

GRABER: Rose and Sarkis Colombosian had a son named Bob, and Bob said his parents used to drive around to deliver yoghurt to Armenians living in the area and to bring containers to ethnic stores in Boston. He also remembered bringing yoghurt to school with him in the very white town of Andover, where his family first lived.

WOLF-MEYER: And so he brings it to school to share with people. And his teacher uses it like, as a moisturizer, right? Like she puts it on her face in order to like, see if that’s what you do with it.

TWILLEY: Evidently Bob’s teacher was not an Adelle Davis fan. In any case, Bob eventually joined the family business and worked on expanding it.

WOLF-MEYER: One of the challenges that you can see is they’re really trying to figure out how to make it palatable for mass consumption. And so part of what they embark on is sweetening it up, putting fruit into it.

GRABER: And when they did that, sales just took off. Americans vastly preferred the fruit-based yoghurt over the plain kind.

TWILLEY: Colombo Yoghurt even started making TV ads to promote their yoghurt to a whole new audience.

BOB COLOMBOSIAN: Hi, I’m Bob Colombosian, and this is my wife Alice. This is my mom, Rose Colombosian. She invented Colombo yoghurt in our kitchen in 1929. The kitchen—it was right about here. My mom cooked yoghurt in a big bucket. It was this big. My brother fell in the bucket once.

ROSE COLOMBOSIAN: We threw that batch away

GRABER: But Colombo yoghurt wasn’t the only one in the market at this point.

TWILLEY: One of the earliest yoghurt entrepreneurs, a Sephardic Jew called Isaac Carasso, had started a business selling yoghurt in Barcelona in the early 1900s. He’d grown up in Greece, eating thick, strained Greek yoghurt, and when the Metchnikoff yoghurt fad got going, he decided to make a business out of it.

GRABER: At the time he was living in Spain, and he decided to call his company Danone. It was from a nickname for his son Daniel, “little Daniel.” Originally, in the ‘20s, Isaac sold his yoghurt in pharmacies, as a health food. He died in the ‘30s and Daniel took over.

TWILLEY: In the 1940s, Daniel decided to leave Europe for obvious reasons. He settled in the Bronx, and renamed the American arm of his company Dannon to try to make it more appealing to Americans. But even with the new name, the yoghurt itself wasn’t flying off the shelves.

HERSH: Americans weren’t taking to it. So he figured he had to do something. Now, he took on a partner, Juan Metzker, and together they came up with a number of innovations. But the first and most groundbreaking was they added fruit.

GRABER: This was the same move Colombo made to appeal to Americans: both companies had realized they needed to make the yoghurt sweeter and more dessert-y, less tangy, less kind of weird and ethnic—at least to American tastebuds at the time.

TWILLEY: But even with fruit and sugar added and with Adelle Davis’s enthusiastic backing, it wasn’t until the 1970s that yoghurt truly hit its stride in the US.

WOLF-MEYER: And that is really tied to the health food movement in that moment. It’s tied to kind of national distribution networks. But the 1970s marks like, a real shift in American consumption of yoghurt.

GRABER: America in the 1970s was going through a lot of changes. As Matthew said, more brands were becoming kind of national brands, supermarkets were getting bigger and bigger. Also people were as he said obsessed with health, a few hippie crunchy ideas were going mainstream, and so Dannon took advantage of this by bringing back Metchnikoff’s legacy.

HERSH: It was their ad that appeared in the 1970s that showed a Soviet Georgian man who was certainly over a hundred years old in appearance.

VOICEOVER: In Soviet Georgia, there are two curious things about the people. A large part of their diet is yoghurt. And a large number of them live past a hundred.

HERSH: And they said, do you wanna know why the people in this region live, many of them, past a hundred? They eat a lot of yoghurt.

VOICEOVER: Of course, many things affect longevity, and we’re not saying Dannon yoghurt will help you live longer. But Dannon is a natural wholesome food that does supply many nutrients.

TWILLEY: At this point, yoghurt had essentially been made into dessert to suit American palates. But it was still being marketed as a health food. And of course healthy is often code for: it will help you lose weight.

WOLF-MEYER: So. Yogurt really finds one of its early markets in women who are dieting.

GRABER: Over the decades since the ‘70s, yoghurt has continued to be marketed as a food that will make you healthy, but the arguments change based on the latest health fads. Dannon launched their Activia line in Europe in the ‘80s and in America in the 2000s, and this one focused on yoghurt’s microbes and their relationship to gut health.

KRISHNA: I remember my aunt used to buy Activia because of those Jamie Lee Curtis commercials. Saying it was good for your gut.

JAMIE LEE CURTIS: So Kate, you were stressed, a lot of junk food on the go, and you were…

KATE: A little irregular, sluggish.

MOM: My daughter needed Activia.

VOICEOVER: Help get your system back on track. Activia with Bifidus regularis helps regulate your digestive system.

GRABER: When it comes to those microbes—of course, fermented foods are good for your gut, we talk about that all the time on Gastropod. Doesn’t have to be yoghurt, there are lots of great fermented foods out there: miso and sauerkraut and pickles and all sorts of things. Yoghurt’s good too.

TWILLEY: Activia was always a little thin and drippy for my taste. But if you, like me, prefer your yoghurt on the other end of the texture spectrum, well, don’t worry: Greek yoghurt is here for you. Greek yoghurt is strained after it’s fermented to make it even thicker and more tart.

HERSH: Why did it catch on? Very simple. Has much less sugar in it. And so it became very popular for people who were on the keto diets, and the paleo diets, because it was really much lower in carbohydrates. So it was pretty much a. A simple reason for it. It was perceived as healthier.

GRABER: And today the fad is not just to avoid carbs but also to seek out protein, and there’s yet another yoghurt for the protein obsessed these days!

ICELANDIC WOMAN: Icelandic Provisions’ skyr. It’s like yoghurt, but packed with more protein and less sugar. And that’s why we have been eating skyr since we were Vikings.

HERSH: There’s a yoghurt to appeal to every single taste and style.

KRISHNA: 100%. I’m still out here in grocery stores looking at the new brand of yoghurt. The obsession will never fade.

TWILLEY: These days, yoghurt is big business almost everywhere. It’s made it in America and it’s still beloved in its traditional homelands. It’s proven adaptable to all sorts of palates and cuisines

KRISHNA: In America, we’re used to, like, scooping our granola and berries on top of our yoghurt. In other countries it’s used as a sauce. In India, you know, we use it in all of these types of dishes. I do feel like it’s, you know, a, a cross-cultural food that speaks many languages.

GRABER: Yoghurt is compatible with a lot of different cuisines, and also it can be both sweet and savory. I personally love to turn yoghurt into like, a sauce for fish with dill and garlic, while my spouse prefers his with maple syrup. Priya enjoys it both ways every single day.

KRISHNA: I have it in the morning in my, I make like a smoothie for myself and I always put that yoghurt in there. And then I have it as an afternoon snack either two ways: either with chocolate chips or with a drizzle of olive oil and salt and pepper.

[MUSIC]

TWILLEY: Thanks this episode to Priya Krishna, June Hersh, Matthew Wolf-Meyer, Luba Vikhanski, and Veronica Sinotte—and also to our favorite microbe expert Ben Wolfe for advice. We have links to their work on our website, Gastropod dot com. And in case you’re having a meltdown because we didn’t discuss froyo, never fear: our dearly beloved supporters will get the full scoop in their newsletter. Get yourself on that list by signing up at gastropod dot com slash support.

GRABER: Thanks as always to our fabulous producer Claudia Geib. We’ll be back with a brand new episode in two weeks, till then!