Instant Genius - What happens in your body when you eat

Episode Date: December 20, 2024

What’s your favourite food? A hamburger, a slice of cake, a pizza? Eating is something we all do every day but most of us rarely think about what actually happens in our bodies after we put food into our mouths. In this episode, we catch up with Dr Chris Van Tulleken to speak about his forthcoming Royal Institution Christmas Lecture series telling us everything we need to know about what’s happening in our bodies when we eat. He tells us what actually happens when we put food into our mouths, what’s going on in our bodies once food is in there, and why farting is just part of the process. BBC Four and iPlayer, 9pm, on 29, 30 and 31 December. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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now. Book on Hilton.com or the Hilton app and save up to 20% to get the stay you expected. When you want savings, not surprises. It matters where you stay. Hilton, for the stay. This podcast is sponsored by name, audio and focal. Streaming has made music more accessible than ever, but true listening is about more than ease. It's about quality. British audio experts name audio alongside french acoustic specialist focal combine handcrafted tradition with cutting-edge innovation and high-end materials delivering digital precision with analog warmth so you can experience exceptional sound at home music just as the artist intended visit name audio.com to learn more hello and welcome to instant genius a bite-sized masterclass in podcast form every monday and

friday you'll hear world leading experts and scientists talking about the most fascinating ideas in science and technology today. I'm Jason Goodyear, commissioning editor at BBC Science Focus. What's your favourite food? A hamburger, a slice of cake, a pizza? Eating is something we all do every day, but most of us rarely think about what actually happens in our bodies after we put food into our mouths. In this episode we catch up with Dr Chris Van Tolligan to speak about its forthcoming Royal Institution Christmas Lecture series, telling us everything we need to know about what's happening in our bodies when we eat. tells us what happens as soon as we put food into our mouths, what's going on in our bodies

once food is in there, and why farting is just part of the process. Welcome to the podcast. Thanks very much for joining us. So nice to be here. We're here to talk about your forthcoming Christmas lecture series. For those who don't know, these lectures were settled by Michael Faraday many years ago and it features a who's-who of scientists over the years. So how does it feel to be part of this? It is incredibly daunting.

there are kind of two main reasons. One is that I watched these lectures as a kid and I went to the Royal Institution and I saw one of the demonstrations I'm going to do, which I'm not allowed to tell you about because we can't have spoilers. And so I'm repeating something that was very inspirational from my own childhood because I think the R.I was a big part of me becoming a scientist and a doctor. But when you are right, you know about the history in the R.A. And then when you're in the building, rehearsing,

you are just surrounded by the portraits of the sort of, of everyone who's created modern science. And every time you discuss an element, it turns out it was discovered at the Royal Institution. It's amazing. I mean, the team, I've got to say, the team still manages to feel very contemporary, so it's sort of that you're aware of the history, but you don't feel bogged down in it, which is nice. I think these are going to be fun, modern lectures. They're not going to be stuffy. In fact, I know they're going to be fun. So why did you choose this topic, and why is it so important for young people? the most important project of all life on earth is eating that's what life does is we take energy from our food and mix it with our breath and extract the energy in between those two things

kids are really interested in this i mean everyone listening knows that you put food in one end and it comes out the other end looking very different and it seems to allow you to do all this stuff that you do and it makes noises and you know it's fun when you put it in and smelly when it comes out so it's a really fun topic that is it's the first bit of science that you can really access the body doing. And so I think kids are interested. The other thing to say, I think it's unavoidable that many kids have difficulties with food. Our food system makes a lot of grown-ups and kids a bit poorly, and kids are entitled to understand why that is, where their food comes from, how it arrives at their lips,

and then how different foods affect them when they go inside their bodies. So I think if kids want to grow up being strong and healthy and performing well. And so understanding food and diet is the most important aspect of all that. So let's have a fun look at this then and start at the beginning. So when we put food into our mouths, we start producing saliva. Why do we do that and how does it work? So digestion starts even before we put food in our mouths.

And anyone who walks in the, you know, they get home from a day at school, you'll know that your mouth starts watering, you make saliva and your tummy will start rumbling. So you start all kinds of changes start happening in your body to prepare you for what you're going to put into it. And saliva is an amazing liquid. You make a litre and a half of it per day and swallow all of it. And it is full of enzymes, some of which start breaking down your food. So you're digesting your food in your mouth. But it's also full of antibodies to clean your food.

So these are little proteins that bind to any viruses or bacteria in the food. So it's a kind of miracle liquid. lubricates the food so that you can then swallow it and it makes its way into your gut where you're going to start digestion begins in earnest. So how about swallowing? I mean, this is quite fun. Even if we eat while we're doing a handstand, we can still swallow. So how does that work? So there's a temptation to think that you put food in the top and it kind of falls through your body because of gravity. But it isn't it. It's propelled through your body by a process called peristalysis, which is a little bit like squeezing toothpaste.

through a tube. And so even if you drink water standing on your head, your esophagus will squeeze it up into your stomach. And we are going to do a demonstration to prove this using my identical twin brother, Dr. Zandt. So now that we've swallowed the food, it's entered our stomach. What happens there? So your stomach is full of strong acid, which cleans the food. Acid doesn't really digest the food. And your stomach has this process called retro-pulsive peristalysis, where it smashes up any particles of food even further. your stomach, the food makes its way into your duodenum, then your jejunum and your ileum. And this is the so-called small intestine, which is very, very long. It's much longer than the large

intestine. And this is where your food is broken down into molecules. So this is lecture one. And we want to look at how enzymes, which are also found, of course, in your washing powders at home, they break down the molecules from all the food stains and blood stains on your shirts and trousers from a busy day at school falling over and having nosebleeds. spilling a lunch all over yourself. So enzymes break down food in washing machines and they break down food in your gut. At the end of your small intestine, you're left with a slurry of stuff called chime, which is all the stuff you couldn't digest. And that arrives at the entrance to the large intestine, the ileococcal valve. And the large intestine is home to this huge community of other

organisms that live inside you and that are you, but they're also not really like you. So you are, you know, the concept of you is going to be shaken up quite a bit in the final part of lecture one because you are not quite just yourself. What you're talking about there is the microbiome. Yes. So what exactly is that? So most of your gut is pretty clean from your mouth through to the end of your small intestine. It's not sterile, but it's not full of bugs. Now inside your colon, all that makes its way into the colon, if you're well, is the fiber, the stuff from your food you couldn't digest, plus the enzymes left over from your small bowel. And the fiber, you can't break it down, but the bugs inside your gut, the bacteria there,

and there are some little parasites too that they need to be there. There are some fungi. They can break down the fiber. They break it down. They produce useful little molecules called short chain fatty acids. And those help your immune system. They help your heart. They help your brain.

And they produce gases as well, which is make up some of the reason you fart. But that's why fiber is good for you, because you're feeding the friendly bugs. And in return, those friendly bugs look after you. They make these lovely molecules and they keep away bad bugs. They stop you, your body being taken over by invaders. So we're going to have a nice, I know I mustn't give spoilers, but we've been working this morning on a very, very fun demonstration to show what happens when you eat a really good diet, high in fiber and you nourish the good bugs inside you with lots of water. What happens when you get ill with a parasite like GR diocese or bugs like cholera? And what happens if you don't eat enough fibre and you get constipated? So

these lectures, we're never going to tell you to eat your greens. These are not about giving you advice. I hope there is no advice in any of the lectures. But by the end of the lecture, you will want to go and eat some fresh fruit and vegetables and make sure that you're nourishing all those friendly bugs inside you and looking after them. You mentioned farting there. So why do some foods make us fart more than others? So there are two answers to that question. Some foods literally feed the bugs more and they make more gas and bugs some of the gas is methane, but some people don't make any methane at all.

They make hydrogen or other gases. So some foods make you make more gas, but there are other foods that make the gas smellier. So there are two things that are going on. When you notice you're farting, you might be noticing they're getting smelier or that there's just a bigger volume. So all those pulses and cruciferous green vegetables, the crunchy green ones, like the kale and the broccoli, all that stuff, they contain sulfur molecules that can make the fart smelly, but they also contain all the fiber that make the bugs produce gas. But quite a lot of farting is air that you've swallowed as well. So farting, I would say, a lot of my patients when I work in the hospital, they're very worried, they get, they feel bloated after particular meals and they feel very farty. Farting is really a sign that you are eating a healthy diet. And obviously there's a moment where some bad bugs can make you fart as well, but generally if you're farting a lot, it's because you're eating pulses, beans, lots of fresh fruit, lots of veg, and it's really a sign that you're doing the right thing. So sticking

with this theme then, what is boo made of? What is poo? So this is a great question. And actually, when, you know, I make a kid show for the BBC Operation Out, some people may have listened to or watched, and I had to go and look up exactly what is in there, because you absorb. You If you're well, you absorb all the fat, all the protein, all the sugar from the food you eat. and your gut digest some of the fiber but not all of this. And we can prove this because if you eat sweet corn, some of it comes out whole in your poo. Even the bugs in your gut don't digest much of the sweet cod.

The poo is made of the food that you couldn't absorb, the fiber mainly, and that binds water. And then up to half of every poo you do is the bugs from your gut. So these bugs multiply very, very fast, and some of them die and some of them stay alive. But if you kept them all in there, you'd explode. So you have to get rid of the bugs in your gut. And about half of every poo you do is made of old, dead bacteria. Well, some of them, of course, aren't even dead. That's a way of getting rid of them.

And then the other bit of a poo, of course, is that the lining of the gut. You make new skin cells that line the gut, and you have to poop out the old dead ones too. There's also some mucus in there, some antibodies, and you'll have a few of those digestive enzymes left. So that's what poo is. But it's mainly fiber, water, and bugs. So perhaps we're very active people We're always running around playing sports or whatever And we get our energy from food

So how does that work? Well, in lecture two I think I can say without too many spoilers There are going to be a lot of bangs and flashes and flames There's going to be a lot of release of energy We're going to burn some stuff And in our body we talk about burning calories As a way of powering

That's what life does But the way we're going to be we do it in our bodies is very, very, very different and far more efficient and sophisticated than when we just burn something in an engine or when we burn something in oxygen. And so we're going to try and celebrate and demonstrate how exactly you hand electrons from your food to your breath and extract energy in between. The way your body does it is by turning, for example, a sugar molecule into dozens of different molecules in a sequence and then finally inflating your mitochondria with electrical charge and releasing that electrical charge to make a final molecule called ATP,

and it's the ATP that causes all the proteins in your body to change shape. And that's what makes you alive. It's the ATP changing the shape of the proteins in your body. Whether you're sending a message down the nerve cell or moving your lips to have a conversation with you, Jason, that's what's going on for all life on planet Earth. And so we're going to try and demonstrate that in about four minutes using a very wonderful colleague of mine and some kids and a very elaborate demonstration. But I think the thing we really want people to leave with is going, your body is a absurdly sophisticated machine that is fantastically more efficient

than any engine at getting energy out of its fuel. So off the back of that, a lot of people say if we eat lots of sugary sweets, fizzy drinks, etc. It sends us into hyper mode. Is there any truth to that? There probably is some truth in that, in the sense that there have been some studies done on the colours that are used in sweets, and there is some evidence that they affect lots of our ability to pay attention. So there are a lot of foods that peculiarly in this country are recommended for children,

but that also have warnings on them saying they may stop you being able to concentrate. So in general, I think if someone is struggling to concentrate, staying away from foods that have artificial colors added, may be a thing they want to think about. I must be careful here not to give anyone any advice, but I think I would, I avoid those foods because I need to concentrate hard during the day. In terms of sugar making people hyper, we have much less evidence. Some kids find that it does, and that may be what we call a placebo effect. Lots of people find that a big sugary meal actually sends them to sleep. So if I eat a big bowl of pasture, it's turned into sugar very quickly in my body. And actually I feel pretty tired. So often the sugar in drinks and

sweets is paired with things that wake us up, either the coloring or caffeine. So if you drink a can of cola, often it's got caffeine in it. And energy drinks all have, it's the caffeine that's waking you up. And in fact, energy drinks are specifically recommended that children do not drink them because they are pretty harmful. So I think I'm very confident. saying kids should not be drinking energy drinks or cola. They're really not good for your bodies. When you need to build up your team to handle the growing chaos at work, use Indeed sponsored jobs. It gives your job post the boost it needs to be seen and helps reach people with the right skills, certifications and more. Spend less time searching and more time actually

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So when the conversation turns to what's next, it isn't about stepping away. It's about continuing the story. Explore your options at kingsley manor.org, a non-profit month-to-month senior community within the Front Porch family. So how about the main food groups? You know, we've all heard about proteins, carbohydrates and fats. How do they affect our bodies differently? So those are the molecules in our food that we get energy from. The fiber you don't get much energy from, but of everything you eat is made of a mixture of one or more of protein, fat or sugar.

So if you eat sweets, they're really just sugar. But if you eat, let's say, a burger in a bun, the meat in the burger is protein, it's muscle protein, and you will break that down into little building blocks called amino acids, and you can use those amino acids either to build your own body or as fuel to run your body. The starches, the flour, the wheat flour, and the bun, that's carbohydrate. You'll turn it into sugar in your body, and then you'll use it. You can store it as energy, or again, you can turn it into muscle. And then fats, similarly, they're a great energy store.

So in general, if you eat a balanced diet of real food, which is a real challenge for lots of people, but if you eat lots of fresh fruit, vegetables, pulses and nuts, if you eat meat, fine, or if there's dairy and there's fish, those are sources of proteins, your body is pretty amazing at getting the balance right, at saying you're full when you don't need any more energy and it's making you go and get what you need from all the different foods. So if people are wondering what to eat or how to balance those things, eating real food that's cooked at home, we know that that's linked to good health. It's important to say that food is often more expensive. It's not easy to prepare. And it's, you know, for the kids listening, I think I want to acknowledge

kids have very little control over what they eat. Kids are fed by grown-ups. You guys are forced to eat the food at school, the food your parents serve you, or the food that your grown-ups serve you. So that's one of the reasons I don't want to tell you to eat a particular thing is you may not be able to go and get that thing. But what I'm trying to avoid is saying you should eat a particular portion of carbohydrate, fat or protein.

If you eat starchy, starchy veg like potatoes, rice, beans, and then you eat leafy and crunchy veg, all the different peppers and tomatoes and salady things, broccoli, carrots. You get fiber, and then you, you eat meat for meat for protein or eggs, dairy, cheese, there's protein in lots and lots of different things. So let's have a look at taste then. So it's Christmas time. So some of us like sprouts, some don't. I mean, personally, I eat pretty much everything, but I hate smoked haddock, for example. So, you know, how does that taste differ? Are you not coming around to mine for

my smoked haddock sprout pie? A Christmas favourite. I love sprouts, but I tell you what, sprouts are much better if you cook them up with some butter, a bit of bacon, and throw in a few chestnuts. That's when the sprouts really come alive. A boiled sprout is a pretty dull prospect, if I'm honest. They're quite bitter. They're much more bitter. They're mini-cabages. So my girls like sprouts because I say they're fairy cabbages, so they can pretend to be giants. I cook them with a little bit of bacon and a bit of butter. And the fat and the salt makes the mini-cabages really tasty. And then they make you really farty and you get smelly farts because of all the sulphur in the sprouts. They're good for pranking people with as well.

Why do we like different things? Taste changes we get older. We usually like things that we've had a good experience with. So if you want to eat something, I mean, the sprout is a good example. Sprouts are really good for you. They're really, really, really good for you. So if you want to eat them but you don't really like them, the more you eat them, the more you will like them.

And pairing them with making them a little bit nicer by adding some butter, for example, adding a little bit of the fat, makes them taste better, or having them as part of a meal, so you eat them with your other food. Gradually you will learn to like them, but sprouts have bitter molecules in them, and a lot of kids really struggle with things that are bitter. And that's for a very sensible reason. Your bodies, kids' bodies, are less able to handle all of the,

I mean, they are toxins, I guess, the things in plants that plants have that they're sort of good for us in a way. They help our microbiome, but you can't overdose on them. So kids have very, very highly developed taste receptors for bitterness, much more than grown-ups, so that they don't eat too many of the poisons in plants. So don't worry too much if they're a veg you don't love. But my rule is, with my girls, they have to try even just like one leaf of the sprout, and then they're done, you know.

Always try a tiny bit. And what you will find is as you eat more and more and more, you come to love them. As a child, I hated sprouts now genuinely I'm going to cook sprouts for tea. weekend. How about something that most people do like then? Desserts. So this is sort of a two-for question. Why are they so appealing and are they really that naughty? So we have a lot of evidence around the common properties of foods that we all love or really the thing that scientists have studies is the foods that we eat too much of because we used to think that people ate too much food because they were greedy or lazy or ill-educated. And now it's very clear that people eat too much

food because of the way the food is engineered. So if you run a food company, say, and you want to get people to really, really love your particular product, it might be a cake, it might be a pizza, it might be a ready meal, it might be a type of crisp. In fact, all of those products that we can't stop eating have very similar properties. They all have a lot of sugar. Your pizza, a lasagna, breakfast cereals, biscuits, all of it. Even the savory stuff has a lot of sugar. It also all has a lot of salt. So even the breakfast cereals and the biscuits have a lot of salt in them. And adding fat to the mixture of salt and sugar and fat seems to be really important. So those three molecules kind of work together. They're not very nice just on their own. You need to add taste that you need to add different

flavors. But those are at the core of almost everything that we really, really learn to love. and what seems important is that the food is soft and that there's not too much water in the food. So soft food with a lot of fat and sugar per mouthful, it's not diluted with water, that seems to increase the reward we get. Because when we eat food, if you get it past the tongue, once it's in the gut, a signal goes to the brain going, hey, there was loads of sugar and fat in that. And whilst we worry about that nowadays, because there's so much of it in our diet, in our evolutionary past, that was really good. If we could find honey, for example, that had lots of sugar,

or you could find very fatty foods, you'd get a reward, and your brain would go, hey, that thing you just ate, that was good. Go and get more of that next time. So what we have now is very soft foods with a lot of sugar, salt and fat that are very cleverly engineered so that they taste great, they come in cool packaging. they're often sold to us as healthy, and those foods we eat too much of. Now, your question was about dessert. In fact, if you go and ask people what they like, they generally like a mixture of pizzas, burgers, fried chicken, puddings, biscuits, crisps, and the salty things are also very sweet, and the sweet things are also very salty. So it's sort of, it's not just as simple as people love dessert.

In terms of how bad they are, well, I want to be really careful here. don't want any young people listening to this to panic about the food they're eating. Food needs to be fun. It needs to be joyful. And food is what binds us together. You want to eat similar food to your friends and that's fine and good. The difficulty is that through no fault of yours, but grown-ups have created a world in which unhealthy food is sold to you as healthy. It is very, very cheap. It is available to you. It's often in your school. It's in vending machines. It's in all the shops on the way to school and from school. And often it's the only food that grownups can afford.

It's the cheapest food by a long way. And so this makes life quite difficult for kids who might want to eat more fresh fruit and veg. My experience, and if someone's listening to science focus, okay, they are going to be a smart, informed young person. And my feeling is my experience of talking to kids of the age that listen to this and and it's the age that listen to Operation Ouches, you all want to be smart, you want to be well, you want to do well at sport, at school, you want to be feeling good all day. And kids are very motivated to eat healthy food. And one of the barriers is that for all of us, the healthy food is expensive and it's not sold to us. It's often not around us. So how bad is it? Look, no one needs

to panic about this as an individual. But my passion as a scientist is saying to, government, hey, you are making unhealthy food very available for kids. You're not warning them that it's unhealthy and it's sold at a point where it's much cheaper than the healthy stuff. So one of the things I think is hard is my seven-year-old, for example, can go into any shop and use her pocket money to buy a can of fizzy pop that's incredibly high in sugar. It's also got acids in it that dissolve the teeth. And there's no warning that even if we just talk about something simple like tooth decay, which is a terrible problem in the UK for all, for all children, there is no warning on a tin or a pack about tooth decay. So my, my passion is not

telling kids that they should eat healthier food. I think kids generally want to do that. It's saying I would like to create a world in which it was easier for them to do this and where they weren't marketed unhealthy food all day every day. But I really want to underline individuals, the kids listening to this, don't go and panic, eat the food in front of you. You are going to be just fine. And the one thing, The one thing we do know is that fresh fruit and vegetables are incredibly good for you. And food in packaging that's made by big companies generally is a lot less good for you, but you don't need to panic about it. Thank you for listening to this episode of Incent Genius, brought to you from the team behind BUC Science Focus.

That was Dr Chris Van Tullochan. To discover more about the topics we've just discussed, check out his Royal Institution Christmas lecture series, airing on BBC 4 at 9pm on the 29th, 30th and 31st of December, and also available on IPlayer. If you liked what you just heard, then please do consider subscribing to Incen Genius on your preferred podcast platform. The current issue of BBC Science Focus is out now. Pick up a copy wherever you buy your favourite magazines or download us on your app store of choice. You can also find us on Apple News or online at ScienceFocus.com. This podcast is sponsored by Name, Audio and Focal.

The texture and emotional depth of music can be lost through digital sources or poor signal. Name Audio believes you can have digital precision with analogue warmth. Alongside French acoustic specialist Focal, Name creates high-end audio systems combining innovation with craftsmanship, so you can listen to music, just as the artist intended. Discover more at Name Audio.com. Thank you.