Subtitles section Play video Print subtitles A few years ago, I always had this thing happening to me, especially at family gatherings like teas with aunts and uncles or something like this. When people come up to you, and they ask you, "So, what are you doing?" And I would have this magical one-word reply, which would make everybody happy: "Medicine. I'm going to be a doctor." Very easy, that's it, everybody's happy and pleased. And it could be so easy, but this effect really only lasts for 30 seconds with me, because that's then the time when one of them would ask, "So, in what area of medicine? What specialty do you want to go into?" And then I would have to strip down in all honesty and just say, "OK, so I'm fascinated with the colon. It all started with the anus, and now it's basically the whole intestinal tract." (Laughter) And this would be the moment when the enthusiasm trickled, and it would maybe also get, like, awkwardly silent in the room, and I would think this was terribly sad, because I do believe our bowels are quite charming. (Laughter) And while we're in a time where many people are thinking about what new superfood smoothie to make or if gluten is maybe bad for them, actually, hardly anyone seems to care about the organ where this happens, the concrete anatomy and the mechanisms behind it. And sometimes it seems to me like we're all trying to figure out this magic trick, but nobody's checking out the magician, just because he has, like, an embarrassing hairstyle or something. And actually, there are reasons science disliked the gut for a long time; I have to say this. So, it's complex. There's a lot of surface area -- about 40 times the area of our skin. Then, in such a tight pipe, there are so many immune cells that are being trained there. We have 100 trillion bacteria doing all sorts of things -- producing little molecules. Then there's about 20 different hormones, so we are on a very different level than our genitals, for example. And the nervous system of our gut is so complex that when we cut out a piece, it's independent enough that when we poke it, it mumbles back at us, friendly. (Laughter) But at least those reasons are also the reasons why it's so fascinating and important. It took me three steps to love the gut. So today, I invite you to follow me on those three steps. The very first was just looking at it and asking questions like, "How does it work?" and "Why does it have to look so weird for that sometimes?" And it actually wasn't me asking the first kind of these questions, but my roommate. After one heavy night of partying, he came into our shared-room kitchen, and he said, "Giulia, you study medicine. How does pooping work?" (Laughter) And I did study medicine but I had no idea, so I had to go up to my room and look it up in different books. And I found something interesting, I thought, at that time. So it turns out, we don't only have this outer sphincter, we also have an inner sphincter muscle. The outer sphincter we all know, we can control it, we know what's going on there; the inner one, we really don't. So what happens is, when there are leftovers from digestion, they're being delivered to the inner one first. This inner one will open in a reflex and let through a little bit for testing. (Laughter) So, there are sensory cells that will analyze what has been delivered: Is it gaseous or is it solid? And they will then send this information up to our brain, and this is the moment when our brain knows, "Oh, I have to go to the toilet." (Laughter) The brain will then do what it's designed to do with its amazing consciousness. It will mediate with our surroundings, and it will say something like, "So, I checked. We are at this TEDx conference -- " (Laughter) (Applause) Gaseous? Maybe, if you're sitting on the sides, and you know you can pull it off silently. (Laughter) But solid -- maybe later. (Laughter) Since our outer sphincter and the brain is connected with nervous cells, they coordinate, cooperate, and they put it back in a waiting line -- (Laughter) for other times, like, for example, when we're at home sitting on the couch, we have nothing better to do, we are free to go. (Laughter) Us humans are actually one of the very few animals that do this in such an advanced and clean way. To be honest, I had some newfound respect for that nice, inner sphincter dude -- not connected to nerves that care too much about the outer world or the time -- just caring about me for once. I thought that was nice. And I used to not be a great fan of public restrooms, but now I can go anywhere, because I consider it more when that inner muscle puts a suggestion on my daily agenda. (Laughter) And also I learned something else, which was: looking closely at something I might have shied away from -- maybe the weirdest part of myself -- left me feeling more fearless, and also appreciating myself more. And I think this happens a lot of times when you look at the gut, actually. Like those funny rumbling noises that happen when you're in a group of friends or at the office conference table, going, like, "Merrr, merrr..." This is not because we're hungry. This is because our small intestine is actually a huge neat freak, and it takes the time in between digestion to clean everything up, resulting in those eight meters of gut -- really, seven of them -- being very clean and hardly smelling like anything. It will, to achieve this, create a strong muscular wave that moves everything forward that's been leftover after digestion. This can sometimes create a sound, but doesn't necessarily have to always. So what we're embarrassed of is really a sign of something keeping our insides fine and tidy. Or this weird, crooked shape of our stomach -- a bit Quasimodo-ish. This actually makes us be able to put pressure on our belly without vomiting, like when we're laughing and when we're doing sports, because the pressure will go up and not so much sideways. This also creates this air bubble that's usually always very visible in X-rays, for example, and can sometimes, with some people, when it gets too big, create discomfort or even some sensations of pain. But for most of the people, is just results that it's far easier to burp when you're laying on your left side instead of your right. And soon I moved a bit further and started to look at the whole picture of our body and health. This was actually after I had heard that someone I knew a little bit had killed himself. It happened that I had been sitting next to that person the day before, and I smelled that he had very bad breath. And when I learned of the suicide the next day, I thought: Could the gut have something to do with it? And I frantically started searching if there were scientific papers on the connection of gut and brain. And to my surprise, I found many. It turns out it's maybe not as simple as we sometimes think. We tend to think our brain makes these commands and then sends them down to the other organs, and they all have to listen. But really, it's more that 10 percent of the nerves that connect brain and gut deliver information from the brain to the gut. We know this, for example, in stressful situations, when there are transmitters from the brain that are being sensed by our gut, so the gut will try to lower all the work, and not be working and taking away blood and energy to save energy for problem-solving. This can go as far as nervous vomiting or nervous diarrhea to get rid of food that it then doesn't want to digest. Maybe more interestingly, 90 percent of the nervous fibers that connect gut and brain deliver information from our gut to our brain. And when you think about it a little bit, it does make sense, because our brain is very isolated. It's in this bony skull surrounded by a thick skin, and it needs information to put together a feeling of "How am I, as a whole body, doing?" And the gut, actually, is possibly the most important advisor for the brain because it's our largest sensory organ, collecting information not only on the quality of our nutrients, but really also on how are so many of our immune cells doing, or things like the hormones in our blood that it can sense. And it can package this information, and send it up to the brain. It can, there, not reach areas like visual cortex or word formations -- otherwise, when we digest, we would see funny colors or we would make funny noises -- no. But it can reach areas for things like morality, fear or emotional processing or areas for self-awareness. So it does make sense that when our body and our brain are putting together this feeling of, "How am I, as a whole body, doing?" that the gut has something to contribute to this process. And it also makes sense that people who have conditions like irritable bowel syndrome or inflammatory bowel disease have a higher risk of having anxiety or depression. I think this is good information to share, because many people will think, "I have this gut thing, and maybe I also have this mental health thing." And maybe -- because science is not clear on that right now -- it's really just that the brain is feeling sympathy with their gut. This has yet to grow in evidence until it can come to practice. But just knowing about these kinds of research that's out there at the moment helps me in my daily life. And it makes me think differently of my moods and not externalize so much all the time. I feel oftentimes during the day we are a brain and a screen, and we will tend to look for answers right there and maybe the work is stupid or our neighbor -- but really, moods can also come from within. And just knowing this helped me, for example, when I sometimes wake up too early, and I start to worry and wander around with my thoughts. Then I think, "Stop. What did I eat yesterday? Did I stress myself out too much? Did I eat too late or something?" And then maybe get up and make myself a tea, something light to digest. And as simple as that sounds, I think it's been surprisingly good for me. Step three took me further away from our body, and to really understanding bacteria differently. The research we have today is creating a new definition of what real cleanliness is. And it's not the hygiene hypothesis -- I think many maybe know this. So it states that when you have too little microbes in your environment because you clean all the time, that's not really a good thing, because people get more allergies or autoimmune diseases then. So I knew this hypothesis, and I thought I wouldn't learn so much from looking at cleanliness in the gut. But I was wrong. It turns out, real cleanliness is not about killing off bacteria right away.