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Élie Metchnikoff

Is there a way to stay forever young? Arpita tells the story of a Nobel Prize winning scientist who uncovered the truth about our immune system and chased immortality.

Episode Transcript Aarati: 0:11 Hi everyone, and welcome back to the Smart Tea Podcast, where we talk about the lives of scientists and innovators who have shaped our world. I'm Aarati. Arpita: 0:19 And I'm Arpita. Aarati: 0:20 How are you doing? Arpita: 0:21 I... am tired today. Aarati and I... Aarati: 0:27 Just especially tired? Arpita: 0:28 Aarati and I were just chatting before we hit record, and I said that I feel like I particularly showed up looking like a gremlin today. And... Aarati: 0:38 She looks great. I think you look great. Arpita: 0:41 This is thankfully not a video podcast, which is maybe for the best for everyone's eyeballs, but I'm looking at myself in the camera display and I'm just like trying to keep my eyeballs open. They're just puffies under my eyes. Aarati: 0:57 Oh no. Oh no. Arpita: 0:57 Okay, well, this is mostly my fault. I definitely went to bed too late and I wasn't even doing anything interesting. Um, and secondly, my... I have two cats and they don't normally sleep with me, but I guess my partner had a lapse in judgment and so they slept with us at night and as you can imagine, they stepped all over me and all over my head and kept waking me up. Aarati: 1:25 What is it about cats and they do that? Arpita: 1:27 I don't know. Like I'm normally really happy. They're normally very well behaved at night and they usually just sleep in one spot, but something about last night, I think none of us. Could find a comfy spot and I don't think anyone slept well, but now I'm just like, you know, in cartoons when they use clothespins to keep their eyes balls open, like that's how I feel. Aarati: 1:50 I kind of had the opposite. It's funny. I had kind of the opposite problem because you're a cat person and I'm a dog person. So of course we have the opposite problems. Like, as you can tell, I'm in a different recording space. So normally I record in my bedroom and the closet in my bedroom has been terrible forever. So we were like, let's redo the closet. Let's repaint everything. And so I had to move everything out into the guest rooms and I'm sitting in my guest room and my dog did not take the move well we literally moved like two rooms down and he's like"the world is ending" and so he was like throwing up and he was just like having a horrible time of it yeah the stress was causing him all these like stomach issues and like"Oh my God, it's really not all that deep." He got over it in a day, but he also wanted to sleep in my bed with me because he was like, you know, this is terrible. Mom, can I sleep with you? And normally he doesn't, but I was feÉlieng like, you know, okay, fine. Arpita: 2:58 What are you supposed to do? Aarati: 2:59 Yeah. Like he's giving you those eyes like, please, my stomach is upset. I have to sleep with you. And so I was like, okay, fine. Get up here. And so he did, but then. I apparently am just the most restless sleeper, so I was like kicking, I was like kicking him in the face, and like, the poor thing, like, he was just like, this is not worth it, and he went back down to his normal bed in the middle of the night, he just got fed up with me, and he was like, nope, like, that's it, bye. Arpita: 3:31 So your dog, Kyro, and I had the same night, apparently. Aarati: 3:34 Yeah, apparently you did, yeah. I was just like, I'm so sorry. This is how I sleep. But anyway, maybe then we should get into this episode so that you can go to sleep right after. Um, so it's your turn to tell a story. So who are we talking about today? Arpita: 3:52 Yes, I'm really excited to tell you about today's story. We're talking aboutÉlie Metchnikoff, who was actually a listener request. Shout out to Margaret for requestingÉlie Metchnikoff's story. But I wanted to start by, I don't know, just like asking you a really broad question. What do you think about the science of aging or the aging industry? What are your thoughts? Aarati: 4:17 Oh, fascinating. My mom actually works at a company that does aging research, and it's really interesting. Like, I think the idea behind it is more about aging well and increasing your health span rather than your lifespan, necessarily. I also studied C. elegans during my PhD, and there's a whole field of study in longevity with C. elegans. They're these little tiny nematode worms that are one millimeter long, and you can actually freeze them, and they will, remain frozen forever. And then you can thaw them like 10 years later, they're alive again. It's like cryogenically frozen worms. You can starve them and they'll stay alive for forever and ever. Like those, well, not ever, but like weeks, you know, they'll enter this state where they'll just stay alive. And so a lot of people have been studying that. So I just, I never studied it myself, but I just found it really fascinating that. These little worms could kind of become immortal for three weeks. You know? Arpita: 5:24 No, definitely like it definitely feels like there are really great model organisms are basically these animals that we study as models for many different types of diseases. And I do think that aging is sort of being thought of as a disease and something to focus on, or like something to understand, A, how people age, and then if we can figure that out, how to either slow it down or maximize life, like you said. And it really is this huge industry, even outside of science, just consumer products that are selling you things in order to not age and live longer. Um, and I feel this is a really good intro becauseÉlie Metchnikoff, who is our scientist today, is thought of as the father of immunology and the person who really brought science to the aging industry. And we will cover this in more detail, but he's actually a person who coined the term gerontology, which is the science of aging. So he really is kind of like an innovator in this field. So I'm really excited to tell you about him. Aarati: 6:27 I'm excited to hear about him. Arpita: 6:29 Okay, so let's dive in.Élie Metchnikoff was born on May 16th in 1845 in what is what we now know as Ukraine. His father was Moldovian and he had an Ukrainian Jewish mother. And we know a lot about his childhood because his wife Olga wrote a biography about him. So she starts this by talking about his childhood and it kind of feels like déjàvu talking about all the other scientists we've talked about, but, you know, he was a really curious and observant kid. He was always chasing bugs and playing outside and, like, looking for animals. He was the youngest of six, and it does seem like he was a very typical younger sibling. He was, seems pretty annoying and very chatty and he really only stopped talking and annoying his parents when he was hyper fixated on something new. So like a new insect or a new butterfly or something like that. So that was the only time that he shut up. So definitely seems part of the course for a younger sibling. Aarati: 7:34 Yes. Arpita: 7:35 So, Metchnikoff was born at a time where modern medicine was really getting started. Um, most people didn't really understand how diseases spread and getting something like cholera or typhoid was super scary. Um, and we covered this in a previous episode, but kind of around the same time, around the turn of the century. A lot of doctors were still practicing bloodletting and, just like we talked about with Joseph Lister, surgery was really barbaric. And really similar to Lister, he, Metchnikoff witnessed all of this suffering and really wanted to do his best to reduce people's pain when it came to medical care. And so his interest really led him to becoming a zoologist. So he's growing up right around the time that Darwin has published his theory of evolution. And like we know, this really changed the way people thought about the world where everyone was really a creationist or believed that God created the world intentionally. And so the main goal of scientists at this time, including Metchnikoff, was to test Darwin's idea that all life on earth came from a common ancestor. And so in his early career, this is what he was really motivated by and what he wanted to really study. So when he was 19, he went to Germany to study marine life on this very small island in the North Sea called Heligoland. And he was working in a lab there and just like somebody else we know, studied nematodes and flatworms. Aarati: 9:08 Yes. Arpita: 9:08 And he wrote his doctoral thesis on the genetics of cuttlefish, and a lot of the work that he did in this early stage was on anatomy and physiology of these species, and one of his interests was digestion, and this will become important later. Aarati: 9:28 Cuttlefish are really interesting creatures, right? Aren't they? This is like a non sequitur completely, but don't they like change color or something fascinating? Like there's something fascinating about them. Arpita: 9:41 I thought cuttlefish were also interesting because of limb regeneration. Did I make that up? Aarati: 9:46 Yeah, you're right. They possess the remarkable ability to fully regenerate an amputated arm. Arpita: 9:51 Yeah. Aarati: 9:51 Nice. Okay. So, yeah. Cause I think a lot of people do, there is, there is some overlap in regeneration and longevity. So I wonder if that also kind of, um, you know, piqued his interest. Arpita: 10:05 I think based on the story, he probably wasn't quite there yet in his scientific journey, but that is a great thought. So after he does this PhD work in cuttlefish, uh, he's 22. He goes to become a docent at Novorossia University. And just like a lot of universities around this time, it was religiously affiliated, even though he was, he publicly said that he was an atheist, which was honestly kind of crazy for this time. Aarati: 10:31 Yeah. That would not be met with, you know... Arpita: 10:34 Yeah, I couldn't really find a lot about his religious beliefs. It was like in a few different sources, it's like Metchnikoff was an atheist. But I really wanted to know more. I was like, based on everything that we know about, you know, Buckland and like all of these people who were so deeply entrenched in the church, because it really seemed like that's where the science happened. I'm like really curious to know how people reacted to this, but, um, yeah, I couldn't really find anything super detailed on that, which is kind of interesting. Aarati: 11:03 Yeah. And especially around Darwin's time, like I would imagine that if you're a scientist, you either have to work to try and kind of fit evolution into your beliefs somehow or you have to be an atheist and completely reject like it almost seems like that at the time it had to be one or the other. Arpita: 11:23 Yeah, definitely agree And Novorossia was also religiously affiliated. But here he became a professor of zoology and anatomy. Aarati: 11:32 Cool. Arpita: 11:33 And while he's a professor, he met one of his students. Her name was Ludmila Fedorovich, and he married her. Aarati: 11:41 Beautiful name. Arpita: 11:42 And we don't really know a lot about their love story, but it's very clear that he cared very deeply about her. Um, however, very soon after they were married, a few years later, she was diagnosed with tuberculosis. Aarati: 11:56 Oh no. Arpita: 11:57 Um, and today TB is you know, you'll be pretty sick, but it's not a death sentence. But in the late 19th century, it was so sad and so devastating. It's also just a really slow and painful death. And so basically, Metchnikoff had to watch his wife very slowly slip away. Um... Aarati: 12:16 Ugh that's so hard. Arpita: 12:17 They traveled, I know. He tried so hard. They traveled to places with like better climate, like sunnier places, like he really tried his best to take care of her, but, you know, as expected, she eventually died. And then Metchnikoff went into a very deep depression and attempted suicide via morphine overdose. Aarati: 12:37 Oh my goodness. Arpita: 12:38 Um, very shortly after that, he, in 1875, he married another student. Aarati: 12:45 Okay. So he took some time, got over it. Wait, how long was it between the two, like? Arpita: 12:51 Uhhh... a year and a half. Aarati: 12:54 Oh, okay. Yeah, not that long. So not, not that much time. Arpita: 12:57 This student's name is Olga Belokopytovya, and she's the one who wrote the biography. Aarati: 13:04 Really good job, really good job with that name. Really good. Arpita: 13:09 And we can maybe a little bit, like, uh, skim over this next section. Olga was a 16 year old high school student. With an interest in natural sciences. Aarati: 13:18 Oh dear. Arpita: 13:19 Yeah, let's just glaze over this. Aarati: 13:21 Okay, because like when you said student, I thought you meant like PhD student, which I was already questioning a little bit, but at least, you know, a master's or PhD student or something would have been. Arpita: 13:31 No. Aarati: 13:31 Yeah. All right. It was a different time. Arpita: 13:34 He was in his 30s and, or maybe like late 20s and she's 16. But anyway. Aarati: 13:39 Not the best. Okay. Arpita: 13:41 Not the best. But this really turns into a little bit of a deja vu situation for him, because very shortly after they got married, Olga got typhoid and got very, very sick. Aarati: 13:51 Oh my god. This is bad luck. I would start to think, like, is it me? Like, am I making these people sick somehow? Arpita: 13:59 I think that's exactly what he thought because he then lost the will to live and this led to his second suicide attempt. He intentionally infected himself with a tick borne disease and he was really just hoping that both of them would die together. Aarati: 14:15 Wow. Arpita: 14:15 Fortunately, this story has a happy ending. Neither of them died, but this second encounter that he had with death, both, you know, like watching a loved one die with his first wife and then watching Olga become very sick and for him to attempt suicide twice, he really changed his outlook on life because they both survived and it felt like he had like a new lease on life. So he was re inspired and he really poured all this energy into his research, but also he became very fascinated with the idea of death and how to avoid death altogether. Aarati: 14:51 Ah, okay. Yeah, I see. I can totally see that. Yeah. Two, two near death experiences will do that for you. Arpita: 15:00 Right. And it's like, he has this very dual perspective, right? Like not only did he near death twice, but he also watched two people who were very, very close to him also deal with death. One who succumbed and then the other who came really close also. So he has this perspective from like a few different angles, um, and then he becomes really interested in death. I was just gonna like put a little aside in here where, you know, throughout history people have tried to live forever. Like, I feel like there's folklores and tall tales and every culture has this story about, you know, people who want to live forever. Aarati: 15:40 Yeah, it's this great like mythical thing too, like the fountain of youth and like, you know, it's this amazing treasure. Yeah, immortality. Arpita: 15:48 And I think what's really interesting is that Metchnikoff enters the story at a really interesting intersection where he's now in the world of science and medicine. So this idea of like, avoiding death is now being met with science and, um, you know, cells and evolution and all these new ideas that are coming into play. So he has this fascination that is like, you know, millennia old, but he also is like, bringing this new insight into the study of death and aging, which hasn't really been thought of before. So he's kind of bringing this conversation at a very interesting time. Aarati: 16:23 Yeah. Arpita: 16:24 So in 1882, he started working at the Pasteur Institute alongside Pasteur himself. Aarati: 16:32 Nice. Arpita: 16:32 He and Olga take a trip to Sicily while he's working there. He and Olga are staying by the seaside at a cottage in Italy overlooking the bright blue sea. They're having a great time. Aarati: 16:44 Sounds beautiful. Arpita: 16:46 I know. So they're really doing the same thing again where they go on these science vacations. Um. Aarati: 16:52 Oh. Oh my gosh, another, another scientist who goes to the beautiful Italian seaside to go to a medical institutions. Arpita: 17:01 For science. Aarati: 17:02 Okay. Arpita: 17:02 For science. He's going, he's going to Italy for science. Um, so while he's there, uh, the sea is home to all sorts of really cool marine creatures and his wife Olga would go out to explore Sicily during the day and Metchnikoff would spend his days in the cottage staring at jars filled with seawater and tiny organisms and he became really fascinated with starfish and their larvae. So he has these big jars and he has a microscope and he's looking at seawater and he's looking at the larva. And while he's looking at the larva, he sees that there are tiny little cells inside each larva. Um, and we, at this point he knew what cells were, he knew that cells existed, he knew that cells made up other organisms. So that part wasn't new, but what he noticed were that some of these little cells inside the larva were eating other bits inside the larva. They were engulfing them somehow. Aarati: 18:07 So they, were they engulfing other cells or just other little, like, random stuff that was within the larva? Arpita: 18:15 The second bit. Aarati: 18:16 Okay. The second stuff. Okay. Arpita: 18:18 The second thing. So he's seeing that there's cells inside the larva. He's also seeing there's some other floaty bits around. And, he sees that the cells are eating the floaty bits. Aarati: 18:29 Oh, okay. Arpita: 18:31 He made a hypothesis that maybe the cells were eating the tiny particles because they didn't want the tiny particles to be there. So it's a defense mechanism. Aarati: 18:42 Oh, interesting. Arpita: 18:43 It does feel, I'm not really sure how you got there, but we'll let the story play out. Okay. Yeah. We're going to let the story play out. So then he was like, can I recreate this? Just like a good scientist. So he start to put thorns into these larvae and he wanted to see what happened. And what happened was that these same little cells came and tried to attack the thorn because it was a foreign object. And as a result of this experiment. He started to wonder if this applied to humans and other organisms, and if there were other cells within us that helped, you know, attack things that were not meant to be there. This story continues on, but we can just pause there, because he makes this really very monumental discovery here, and he's not even entirely aware of it. Aarati: 19:38 I was just I was just gonna ask, so is he, does he realize at this point that it's very, like, it's very particular specialized cells that are making the attack or has he not figured that out yet? Arpita: 19:52 He has not figured that out yet. So yeah, let's just, let's continue. Aarati: 19:56 Okay, let's, yes. Okay. Arpita: 19:59 I feel like we're both thinking about the same thing, but yeah, let's, let's let Metchnikoff lead us there. Aarati: 20:05 Okay. Yes. Okay. Sounds good. Yes. Arpita: 20:09 So after this, he finds this and he's like, there's these tiny little cells that have this job that is to eat floaty bits. And he becomes really interested in the study of microbes. And especially in this idea that maybe there are these natural defense mechanisms. And so this was really the beginning of. Immunology as a field. Like, people did not believe that our bodies had defense mechanisms at all, they just thought that they were vessels for sickness. And it was like, you were going to get sick at some point, and once you get sick, you're entirely screwed. Like, your life is over. Aarati: 20:44 Oh, interesting. Arpita: 20:45 But didn't necessarily believe that your body had ways to fight it off. Aarati: 20:51 So that's an interesting thing. Cause I, I never thought about that before because a lot of times when I get sick, like with a cold or something, I'm just like, whatever, I'm just going to ride it out and drink tea and let my immune system take care of it. And I sometimes don't even take medicine, really. I just wait for it to go away. But it sounds like. At the time, it, it was like, you either have a treatment or you don't. And so people hadn't realized that, I guess, you can recover without taking a medicine or taking a treatment? Arpita: 21:24 Um, you're thinking about this very much like a scientist, and you remember that most people were very religious, and so they probably just thought that God allowed them to live or didn't allow them to live. Aarati: 21:35 Ah, okay, okay, interesting. Okay, yeah, that, that doesn't, okay, yeah, you're right. I was thinking about it very, very scientific, too scientifically. Arpita: 21:45 You were too scientific, you were too scientific. Aarati: 21:47 I need to take my mind back to the 1800s, early 1900s. All right. Arpita: 21:52 Yeah, you do. Um, because yeah, like people didn't really believe at this time, I think this was maybe just at the cusp of when this mentality was changing, but people didn't really believe that their bodies had this ability to fight disease. Um, and so Metchnikoff realizes that different from larva, which are, you know, just a few cells clustered together, um, for starfish, that in animals that have blood and more complex organisms, um, there's a very special type of particles. This answers your question called a white blood cell, which gathers at any injury site. And he hypothesized based on what he learned with the starfish that the white blood cell allowed the body to kill and remove bacteria and microbes. And so he discusses this hypothesis with his colleagues who suggest to him the term phagocyte, which is a cell that engulfs, um, for us, for all of these particles that he finds that can surround and kill pathogens. And so pathogens are just anything that we don't want in our body or foreign invaders. Aarati: 23:00 Right. Arpita: 23:01 Yeah. So that was, that was got there eventually. Aarati: 23:06 Yeah. It's, it's really hard when you already know the answer. Arpita: 23:09 I know. I know. Aarati: 23:10 In hindsight, like, yeah, but Arpita: 23:13 It's like difficult.... it's difficult to sit in the 21st century and hear about some of these discoveries because it seems so obvious. Like, it seems like such a core facet of how we think of, like, what you just said about you being sick. It's like, you just, you know, people say things like, oh, let your body do its thing, you know? Aarati: 23:30 Yeah, yeah. Arpita: 23:31 They didn't know that. Or even with, you know, Lister, it's like, oh, we should probably clean things. Aarati: 23:37 Yeah. It's like so basic. Arpita: 23:39 It feels basic. I know. And this next bit is actually really interesting because we're sitting here talking about how obvious this is, but this is 1883 and he presents his findings for the first time where he's like, there are these types of cells that are native to mammals and all these different types of organisms that are meant to fight disease. And this was not well received. Aarati: 24:00 Of course not. Arpita: 24:01 So just a little bit of background. So Metchnikoff has sort of this messy relationship with the scientists that are contemporary to him. So Pasteur loves him. Um, he's like working with him. He's at the Pasteur Institute and he loves him. Um, on the flip side, there are a lot of German scientists who don't like him, um, because there's a lot of tension between Germany and France after the Franco Prussian War, and he is in Paris at the Pasteur Institute, so a lot of German scientists are like, no thank you. He did have a lot of French and British scientists in his corner, including our friend Joseph Lister, who supported him very early on in this theory. Aarati: 24:44 I was gonna say, I wonder what Lister thought about this. I think he would be a fan. Arpita: 24:49 Lister was a very big fan. Um, Metchnikoff also had a little bit of a temper, and so it was very difficult to get people on board with his theory, both for political reasons and personal reasons. There was also a competing theory, which I think we've alluded to in past episodes, so another scholar named Robert Koch defended humoral theory, which is the idea that the body is made up of four humors, black bile, yellow bile, phlegm, and blood, and that an imbalance of these different humors causes disease. So Metchikoff is presenting a competing theory that says that the humoral theory isn't actually a real thing. And it's these microbes that are causing disease. And there are these phagocytes or certain types of cells in your body that are preventing disease. And it, the bile or the humoral theory is actually not something that has a lot of weight behind it. So this was very controversial. After he presented this, his findings for the very first time, um, a lot of scientists were very eager to try to replicate his results. So these results were replicated in many different organisms including mammals, um, like larger animals like dogs and cats and also you know, in smaller organisms that were much simpler like worms and lizards and other reptiles. Um, there was also another line of research that was trying to quantify the response. So they were looking under a microscope to see how many cells are these white blood cells showed up at a site of injury and what they found, which is again, maybe a little obvious to us in the 21st century that the bigger the injury or the bigger the insult, the more white blood cells that came to the site. So they were able to count the number of cells and see how many they were and realize that it was actually proportionate. After all of this work and other people supported him, um, he was eventually awarded the Nobel Prize in 1908 as the father of immunology. Aarati: 26:44 Wow. And I just, I just had a thought too, like going back to the beginning of this episode, the fact that this is happening in all the animals that people tested also really supports Darwin's theory, right? That all animals and all living things came from a common ancestor. The fact that we all have this very similar defense mechanism really speaks to that. Arpita: 27:07 Definitely. I think that is spot on. Um, at this point, Darwin has been around for maybe around like 40 or 50 years. So it's not quite as gratingly new, but it's still something that people are working on getting behind. But I totally agree that even though it's not as hot button, it is something that supports his theory, which is great. Aarati: 27:30 Yeah. Just keep, just keep adding to the pile of evidence. Arpita: 27:35 Yes. Agree. Agree. Aarati: 27:36 Yeah. Arpita: 27:37 Okay. So he's won the Nobel Prize. Um, at this point he is super famous. He's a really famous scientist. He is a superstar. People are obsessed with him. He basically has like rock star status at the Pasteur Institute. Like he can do whatever he wants. He's won a Nobel Prize. Aarati: 27:52 Yeah. Arpita: 27:53 Um, he also has a little bit of a savior complex. He wants to spread his gospel on microbes and immunology. Like, he really cares about this. He's like, microbes are what causing all the problems in the world. And so when he wrote on public transportation, he would, he would just like tell random people to be careful about microbes. Um, Aarati: 28:15 Oh, so he's like a hypochondriac a little bit. Arpita: 28:18 I think it's more that he Just feels like everybody needs to know this truth that he has discovered. Aarati: 28:26 Yes. Yeah. Spread the knowledge. Arpita: 28:30 Exactly. Aarati: 28:30 Okay. Got it. Arpita: 28:32 So he boils everything he eats, even fruit, like peeled bananas or peeled like oranges and stuff. He thinks the peel isn't good enough. He thinks that skin doesn't protect you. So he was pouring boiling water on his skin. Um, if he went to a restaurant, he would boil and sterilize all his utensils because he didn't want to deal with microbes. So he's definitely a super fun guy to have. Aarati: 28:55 Yeah. It's, it's, it is, it is like a hypochondriac slash OCD kind of thing has developed here, which is not good. Arpita: 29:04 Yeah, definitely. I totally agree. Um, but then, you know, his interest in microbes sort of expands. So he goes back to his fascination with death and like preventing death. And he zeros in on this one idea that the body is being poisoned as we age. So thinking back to his early days, studying nematode digestive systems, he thought that the root of aging was in the large intestine. So while he was studying different animals, he realized that animals like dogs and cats have really extensive digestive systems compared to birds and lizards. And he also notices that reptiles and birds tend to live a lot longer than dogs and cats. So he was really looking like at the tortoise and he's like, this is living for a really long time and their digestive system is very simple relative to these bigger mammals. Aarati: 29:56 Yeah. Arpita: 29:57 And so then this led him to conclude that the large intestine must be causing direct harm to human lives. Aarati: 30:03 Okay. That's actually not like that illogical of a leap. Like now we know that, you know, the microbiome is a thing that affects your health. And so I'm actually quite impressed that he pinpointed the digestive system and the large intestine in any sort of capacity. That's actually quite impressive. Arpita: 30:21 Yeah. I think you're going to be impressed by the rest of the story then. His idea that the large intestine was bad, wasn't necessarily this like very new idea. Um, people have for a long time before this believed the digestive system was bad for the body. Because even before we knew about germ theory, even before we knew about microbes, people knew that what comes out of your digestive system in the back end is really yucky and we should avoid that. And so people just thought that everything that happens in your intestines before it exits your body is also bad. So people just thought that the intestines were a cesspool. Um, so moving this idea into the 20th century, Metchnikoff thought that the intestines had microbes that caused rotting, which caused the deterioration that was associated with aging. And so his big question was, how do we prevent these microbes from basically eating us from the inside out? And while he was trying to answer this, he learned that in Bulgaria, there's this entire population of centenarians. And centenarians, of course, are people who live to be 100 or more. And he is obsessed with people who live forever because he's trying to escape death. He's like, How do I beat this in some way? So he goes out to find what this village is doing differently and drum roll. It's yogurt. Aarati: 31:47 Yogurt? Really? Wait, what? I mean, okay, interesting, because yogurt has all these like, probiotics, so I see some connection there, but I didn't think it would have that big of an effect. Arpita: 32:03 You're totally on the right track about the probiotics, the microbiome, you're right there with Metchnikoff right now. So he proposed that the toxic bacteria in the gut, like all these microbiomes, could be killed by lactic acid and what we now know as probiotics, which are found in fermented milk and yogurt. And he goes so far to say that yogurt will prolong life and prevent aging and make people live forever. And he called probiotics orthobiosis, which was very new. Basically, this idea of probiotics in general was ignored during his lifetime. Nowadays, we talk about it all the time and how important it is for gut health, but people didn't catch on to probiotics until actually the mid 1990s. So many, many Aarati: 32:47 Oh, wow. Arpita: 32:48 century later. So back to his yogurt discovery. In 1904, he gives a talk to the public. So not just scientists. And he starts off by talking about how bad aging is. And he's like, people are no longer useful to society. They're totally useless as they age. They're in pain. They're close to death. And he tells the audience about this amazing discovery he made. That yogurt can prevent aging. And he's like, there's these people in Bulgaria who are living to be over a hundred. They're eating yogurt every day. And he's kind of like used car salesman a little bit. Aarati: 33:25 Yeah, I can totally imagine it. Did he just, did he also just start eating like a ridiculous amount of yogurt? Arpita: 33:31 He does do that. Yes. Aarati: 33:33 I, I, yeah, I knew it because I was like, this guy's boiling his knives and forks and he's, he's just going to consume gallons of yogurt now. Yeah. Arpita: 33:43 So he's kind of a salesman and his audience aren't scientists, right? So there's still people who are like clinging to humoral theory or don't believe that science is real in the first place. So he's really trying to play to people's emotions to be like, aging sucks. Like we don't want to age. Like how do we not age? Aarati: 33:57 Yeah. Arpita: 33:57 And. Whatever he said, it worked because this started a global craze for yogurt. Yogurt was everywhere. It was on newspaper headlines all over the world. Doctors were recommending yogurt to their patients. They used it as like a disinfectant on like, for surgeries. I know. Aarati: 34:15 Oh, oh my God. For surgeries? Oh my god. Arpita: 34:18 Yeah. Aarati: 34:19 Okay. Arpita: 34:19 Um, pharmacies were carrying yogurt, like people could not get enough. And even brands that we know today, like Kellogg and Dannon, got their start in the yogurt industry. Aarati: 34:30 Oh really? Arpita: 34:31 Um, and the fact that we even today eat yogurt, like I had yogurt for breakfast this morning. Um, the fact that we even eat this and the fact that it is so common and so many different cultures and that it's actually one of the most common quote unquote health foods in so many different cultures. is really because Metchnikoff popularized it. Like, yogurt was not a thing until he said that it was something that could make people live forever. And like, now I think yogurt has sort of moved away from that, but it's still considered a very health food. Aarati: 34:59 Oh, yeah. Arpita: 35:00 And the only reason that we eat it in so many different forms is because of Metchnikoff. Aarati: 35:05 So that's so, that's so funny. My mom is going to be so happy about this episode because yogurt is like her comfort food, like health benefits aside. She doesn't, I don't think she even really cares about that. Although that's a good perk, but she just like, whenever she's like, Oh, what do I want to eat? It's yogurt. She wants to eat yogurt. So she's gonna be really, she's gonna be so happy. Arpita: 35:28 She's a big thank you to give to Metchnikoff because yes, definitely him. So he is a celebrity. He's a crazy celebrity, but he's a celebrity and people worshipped him. But you know, like all celebrities, people also hated him. So he also got a lot of negative publicity about the yogurt, that he was crazy, that he was a quack. Um, he was making all these claims that, you know, yogurt was the next snake oil that was going to, you know, cure everyone. Um, and he took this really personally. So he started to change his stance and he explained that people going crazy for yogurt wasn't what he actually wanted. What he really wanted was for people to accept this theory that aging was a science and something that could be prevented with science. But he really did think that the mania was quite silly and that he never really believed that it was going to cure everything, but just wanted people to understand the science of aging. Aarati: 36:24 Yeah. Arpita: 36:24 This became abundantly apparent when in his mid fifties, he started having kidney trouble and started worrying about his own mortality. And as much as he thought about aging and preventing death and for all his yogurt consumption, because he ate it every single day, he was not able to prevent any of the changes in his own body. Despite all of this, he's still obsessed with the fact that aging is one of the world's biggest problems, and there was hardly anybody studying it. And so he comes up with another theory that if people live long enough, they will develop a death instinct. So there's this quote where he says,"This instinct must be accompanied by marvelous sensations better than any other we are capable of experiencing." So basically what this means that at a certain point he thinks that once we've lived long enough that that the death instinct would kick in and people would be happy and willing to accept death. Aarati: 37:20 Oh, interesting. So it's like, like a psychological thing that you're like, okay, I've lived a full life. Arpita: 37:27 Yes. Aarati: 37:27 I'm done now I can go now. And it would be kind of like a calming thing because like when you're young, you're scared of death. But then the older you get, a lot of times people are like, okay, I've accepted it. I've lived a good life. And that's what he was calling the death instinct. Arpita: 37:44 I think it's even more than that. I think it's less of an acceptance, but more of a willingness, like, people want to die now. Aarati: 37:50 Oh, okay. Taking it a step further. Arpita: 37:52 Like their instinct now is that their life is over and now they want to die. So I think it's less of this, uh, you know, like yeah. Acceptance or just like Aarati: 38:01 passive. Yeah. Arpita: 38:01 Yes. Aarati: 38:02 It's, it's less passive. Yeah. Arpita: 38:04 Exactly. So, he goes to this very large French hospital, La Salpeterre, I don't know how to say that. Aarati: 38:13 Okay. Nailed it. You're not French? No? Arpita: 38:18 Um, which is kind of infamous. It's this public hospital, so people are generally kind of scared of it. So it's public, it's maybe not the best care, and to say this in maybe like the least morbid way possible, Metchnikoff goes there to interview people who are probably going to die. So he goes around asking them what they wanted, and he's asking them how they feel, and he's really hoping to find this death instinct. And he's disappointed because even like really old people who are sick and like very clearly going to die soon did not want to die. And this hospital was this like really sad place that you probably didn't want to be and even then even in these like horrible circumstances where people are sick they're in this kind of like sad place, they don't want to die. They want to live and so after he experienced this and he saw that you know, maybe the death instinct isn't something real or isn't something that people are able to explain... Aarati: 39:16 Yeah. Arpita: 39:17 He doubles down on the fact that aging is a disease and science is the only way to cure it So he elaborates on this theory and says, if we can cure aging because it's a disease through science and people live until like 150 or 200, then at that point, the death instinct finally will appear and people won't suffer anymore. So his idea was that instead of having this like, long, elongated period where people are not mobile, they're suffering, they're in pain, they're sick, they just don't have that, and when they're at the end of a long, happy, full life, they will welcome death, and that's when the death incident will happen, and there won't be any more suffering. Aarati: 39:59 Interesting. I would have thought it would be the opposite, almost. Like, Again, kind of getting morbid, but you know, I would almost feel like if you did have a really long, painful illness at the end, you would just be like, please... Arpita: 40:14 Get me out of here. Yeah. Aarati: 40:16 Like, you know, but he's, he's actually coming up with the opposite idea. That I don't know, there's some like satisfaction to be achieved from living a happy, long, fulfilling life. Arpita: 40:28 Yeah. No, you're totally right. And so he chases this death instinct, but I mean, he had these really big dreams, but he was also a sick man. So he doesn't actually end up solving the mystery of aging. Um, he dies in 1916 in Paris from heart failure, likely related to his kidney trouble. He donates his body to science and medical research, um, and his urn is actually still at the Pasteur Institute in Paris. Aarati: 40:56 Oh, cool. Arpita: 40:57 Yeah. He definitely had a very wacky personality. In addition to that, like he's Russian and he's Jewish, and so he puts him as kind of an outsider in the very largely British, German, French medical scientists that he was contemporaries with and hanging out with. It also really seems like, based on the story, that he had, like, no chill whatsoever. Like, I, like, I said that he had a temper. But he was also one of those guys who was really smart and also knew it. So after reading all about him, he really strikes me as the kind of person who sits in the front row of the classroom and answers all of the questions, but like in a really annoying way, like he's kind of a know it all. It really does make sense that his colleagues had very mixed feelings about him that they were like not always super excited when he was like, hey guys, I have this new thing. They were like, okay, what now, bro? Yeah. Aarati: 41:55 What now yogurt boy? Arpita: 41:57 Exactly. I really think that's how people viewed him because he's kind of a know it all. Aarati: 42:03 Yeah. Arpita: 42:03 Um, you know, all that aside, he was very talented and he had this drive to solve aging, which opened up this new field of immunology and innate immunity and gerontology, which continues to be a big area of research today. Aarati: 42:17 Oh my god. I forgot that he like started immunology at the beginning of this. I was like all into, because I was like,"Oh yeah, the microbiome." He's actually like for all his eccentricities, he's not that far off because I still know, like, there are aging studies where people are connecting diet to longevity. I actually know scientists, like actual scientists who have changed their eating habits in order because of their research because of like their research into longevity and they're like, you know, Oh, I figured this thing out. And so I'm going to eat foods that are high in this particular nutrient or whatever it is. They're like, eating an abundance of avocados or something and I'm like, all right. You do it. Arpita: 43:04 I completely agree with you So, you know is in some ways he was for sure ahead of his time. Aarati: 43:08 Yeah. Arpita: 43:09 But in some ways also Aarati: 43:12 A little bit weird? Arpita: 43:13 Yeah Aarati: 43:16 Just a little bit... but, you know, genius, amazing. Arpita: 43:20 Yeah. So that's the story ofÉlie Metchnikoff. Aarati: 43:23 That was a really good story. Thank you so much to Margaret. That was a great recommendation. Thank you so much. Um, I love it. Thanks for listening. If you have a suggestion for a story we should cover or thoughts you want to share about an episode, reach out to us at You can follow us on Instagram and Twitter at smart tea podcast and listen to us on Spotify, Apple Podcasts, or wherever you get your podcasts. And leave us a rating or comment. It helps us grow! New episodes are released every other Wednesday. See you next time!

Sources for this Epsiode

1.Podolsky, Scott H. "Metchnikoff and the microbiome". The Lancet. Volume 380, Issue 9856, P1810-1811, November 24, 2012. DOI:

2.  "Élie Metchnikoff". Wikipedia.

3. Ilya Mechnikov, Elie Metchnikoff in French (1845-1916). The Institut Pasteur. 

4. Gordon, Siamon. "Elie Metchnikoff, the Man and the Myth". J Innate Immun. 2016;8(3):223-7. doi: 10.1159/000443331. Epub 2016 Feb 3. PMID: 26836137; PMCID: PMC6738810.

5. "The Man Who Cured Aging". Throughline. NPR.

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