That Neuroscience Guy - The Neuroscience of Food

Episode Date: August 1, 2023

For everyone, food is essential for life. For most people, food is an avenue to enhance life. But how do food and taste impact our brain? In today's episode of That Neuroscience Guy, we discuss the neuroscience behind eating food. 

Hi, my name is Olof Kregolsen, and I'm a neuroscientist at the University of Victoria. And in my spare time, I'm that neuroscience guy. Welcome to the podcast. Well, we eat food all the time, right? It's a key part of being alive. No food, no alive. And we usually enjoy food, although there's times where we don't enjoy food. You know, sometimes it's just something you don't like.

Sometimes you have to eat something out of necessity. I know that every time I go camping, I'm always a little bit concerned about freeze-dried food and how it actually works. But there's a lot of times that I love food and all of you love food. So on today's podcast, the neuroscience of food. I'm going to start by saying we've covered bits and pieces of this across the seasons of the podcast, but I just thought I'd try to pull it together because again, as with most of the episodes here in season five, these are ideas sent in by you, the listeners. So remember, if you do have an idea for an episode, you can follow me on Twitter at ThatNeuroscienceGuy and DM me. Or you can just email us, ThatNeuroscienceGuy at gmail.com.

So let's start with how food works at a simple level. At least how our brain processes food. And we're going to talk about a couple of other cool things. So taste, we've talked about taste a bit in the past, but basically for a review, your tongue has a whole bunch of receptors underneath it, receptors for bitter, sour, salty, sweet. And those receptors are stimulated by a chemical reaction from the food itself. When the food hits your tongue, there is a reaction that occurs and those receptors fire depending on what the food is made out of. And basically there's a couple of key nerves that

carry that information back to the brain. There's the facial nerve, it's one of the cranial nerves, number seven, and the glossopharyngeal nerve, which is cranial nerve number nine. And those nerves are primarily responsible for carrying the sensations from these receptors first to the mid brain. They come to a place called the medulla oblongata in the midbrain, which is right in the brainstem. And then from there, that information is passed up to the thalamus. And from the thalamus, it goes to the gustatory cortex, which you can think of as your primary taste cortex.

And that's in the insula. And that's when those nerve signals are given meaning. And how that works is basically experience. You know, when you, from a young age, when you try food and stuff, your brain stores that information and it associates different patterns of activity with different tastes, because things that you taste are a combination of all of these things. Now, smell plays a crucial role in this as well. You might know that a lot of the sensation of food comes from smell. So we've talked about smell again in the past, but basically the way it works is you've got olfactory regions in the nose that are sensitive to molecules that you smell.

And it's almost the same thing. These molecules bind and stimulate the olfactory regions. And that is where the olfactory bulb comes in. And the message is sent to the midbrain again, it ends up in the thalamus and the hypothalamus. And it's sent to parts of the brain like the cortex, which is your sort of cognitive memories of the smells. And it's also sent to the limbic system, the emotional parts of your brain and all those other things, because smells can also trigger sensation or experience. So you've got taste coming in from the tongue through sensory receptors, and you've got smell coming in through the nose, and the primary gustatory cortex and the

primary olfactory cortex work together with the rest of the brain to create the sensation of the food experience. So your experience when you eat something is a combination of these two key systems. But there's even more to it than that. What about texture? Those of us that have done the parenting thing know that when kids are young, texture of food is really important for them. And there's times where the texture alone can turn them off. So where do you get the sensation of texture? Well, we've talked about the fact that your body has sensory receptors all over it, and that includes your mouth and your tongue as well. So when you're eating, the sensation of texture is a physical stimulus, all right? So that's getting added to the mix as well. And that sensation, again, travels from the tongue

up through the midbrain and ends up in the primary sensory cortex, where that piece of information gets integrated with the food experience as well. So from just a purely sensory sort of aspect, that's how food works. You've got the primary gustatory cortex providing the tastes. You've got the primary olfactory cortex providing the smells. And you've got the primary sensory cortex adding texture. But of course, it's more than that as well. For instance, our old friend, the amygdala. It seems like I mention the amygdala in every episode,

but that probably tells you how important it is. If you have an emotional response to the food, like you really, really enjoy it, well, then the amygdala is going to fire and it adds that emotional component to it. And it might not be something where you start crying tears, but at the same time, there's something there. And of course, that sensation of pleasure or enjoyment also involves our friend dopamine, the neurotransmitter. So when you eat things that you enjoy, there is a release of dopamine, which is part of the pleasure sensation. It's a bit more complex than that. We've talked about it in the past, but the amygdala and the midbrain dopamine system are adding to the story as well and of course last but not least there's memory your memories are enacted when you eat food and

they play a large part in biasing you if you will i was recently in the united kingdom and every time i go i go to a little place in west lond Twickenham. I lived there for a couple of years when I was younger. And I always go for at least one curry and usually many. And I really enjoy going for a good curry. It's something that's pretty high on my list of things I love. But when you go for a good curry, part of this is memory. And you have to think about not just your memory of how good the food was, but your memory of experience. So I wanted to add this piece in so you can ponder this, but

part of your enjoyment of food is the associations you have with other experiences in your life. So for instance, my memory of curry when I eat it is Twickenham and friends and a couple of the happiest years of my life. And that is part of the food experience. So those memories that are there when you're doing this, and this might be triggered when you sip a glass of your favorite wine or, you know, you eat something you enjoy. Now, if I'm going to talk about, you know, how food is a pleasurable thing, we also have to talk about why you might not like food. Basically, it's the same pathways, but the experience you're having is a negative one. It just tastes bad. So just like you, everyone sees things slightly differently. You know, you might look at a sweater and think it's great. Your friend might look at the same sweater and think it's ugly.

This is true for the taste and the food experience. A pattern of neural activity that is the taste of the food, if you will, or the food experience, you might interpret that as something that's disgusting, whereas a friend of yours might interpret it very differently. Now, it's not just a learned thing or a translation thing. Basically, there's a subset of people, for instance, that find certain vegetables to be unbearably bitter. And it turns out these people typically don't process dark chocolate or coffee the same way as well, and even beer. And in this case, it's actually genetic.

All right. There's a gene, TAS2R38. It's basically a taste receptor, number two, and it's the 38th member of the family. And this taste receptor gene impacts the way you perceive bitter tastes. And if people have variation in this gene, because not all genes are the same, basically it means you might be hardwired to not like something. So if you're a parent and you've got kids and they tell you they don't like something, you do have to play this game of do they really not like it? Or is it really something where it's wired within them, right?

Where they literally don't like the flavor because that's the way they experience it. So when we have the food sensation, there's a lot of stuff that's learned in the sensory experience, but it's hardwired in part as well. learned in the sensory experience, but it's hardwired in part as well. And I always want to emphasize this, just as we are all different on the outside, we're all different on the inside, right? Our brains are all different and the way we process things is different. A question that came up, which we've actually talked about in the past, but I thought it'd be a fitting way to wrap up this podcast on the neuroscience of food is are there super foods? And the answer is yes and no. For instance, I've mentioned this in previous episodes. There's no doubt that simple carbohydrates are bad for your brain. There's tons of research that shows that that rich sugar diet that we're on impacts cognitive function

and not in a positive way. It has a negative impact. So you could almost say that these sort of artificial sugars are an anti-superfood. But in terms of the berries and things that are out there, I think of acai berries and some of these things, there's really no conclusive evidence that these things are guaranteed to be superfoods, like they're really going to be there and make your brain function better. Yes, if you watch certain shows or read certain articles, they'll make strong cases for them. They'll claim that there's scientific evidence supporting the fact that these superfoods are out there.

The truth is the evidence isn't great. And if you go back through some of the episodes I've done about how to interpret scientific evidence and things like that, you might be able to see why that is. And I guess there's always just the common sense test. If there was a superfood that made our brains function better than anything else, well, guess what? We'd all be eating it all the time. Our doctors would be prescribing it as opposed to it being something that's rumored to be good for you. And I've said this so many times, I don't want to spend a lot of time on it, but diet is a crucial part of brain health.

And the best diet you can have is a simple, well-balanced diet following modern guidelines. I like to use the Canadian Food Guide, the new version, because I'm Canadian. I'm sure there's something similar in other countries. But basically, lots of vegetables reduce red meats and reduce those simple sugars. You know, carbohydrate intake overall comes down unless you need it because you're exercising a lot. So the best superfood out there is just the healthy, well-balanced diet. Anyway, that's all I've got for you on the neuroscience of food. Hopefully you enjoyed that.

Remember, check out the website, thatneuroscienceguy.com. There's links to Patreon where you can support us. Just Google Patreon and see how it works. There's our Etsy store. Thank you to the people that buy t-shirts. We really need to get some more stuff up there. I say this all the time, but we're just limited with time and what we can deliver with just being Matt and me. Of course, Twitter, you can follow me on Twitter at that Neurosci guy.

I am going to make a presence on the new version threads, I believe it's called, especially with the renaming of Twitter recently, but I'm not quite there yet. And of course, thank you for listening to the podcast. It means so much to Matt and me. And please subscribe. My name is Olof Kregolsen, and I'm that neuroscience guy. I'll see you soon for another episode of the podcast.