Food for Thought!

This week we're cooking up a storm, dissecting the science behind food and flavour.
12 August 2014
Presented by Ginny Smith, Kat Arney
Production by Georgia Mills.


The Naked Scientists have food on the brain this week, as we hear about how sound can affect taste, why our mood can be changed by what we eat, and we try out some unusual flavour combinations. And in the news; why grizzly bears may help us in the fight against diabetes, the comet chaser that has finally reached its target, and self-assembling origami robots...

In this episode

Origami Robot

01:02 - Origami robots

Scientists have made origami-inspired robots that are capable of folding and unfolding themselves.

Origami robots
with Sam Felton, Harvard University

Origami was once the traditional art of folding paper into ornate shapes; now it's inspiration for the next generation of cyborgs. Robotics expert Sam Felton has built a real life transformer that starts as a flat piece of paper, then, with the application of heat, it bends itself into a shape and can even crawl around. Graihagh Jackson investigates...

Sam -   One of the great things about origami is, it is capable of very complex structures.  Theoretically, origami can produce almost anything that you could want to use.

Graihagh -   So, what have you designed and built?

Sam -   So, we've built a self-folding crawling robot that can fold itself completely autonomously.  It starts off looking like a roughly rectangular flat sheet, almost like the outline of a robot. And then once it fold itself, it looks more like the origami pattern of a bug or a crab.

Graihagh -   Why?  What was the inspiration behind your design?

Sam -   So, we're originally interested in making robots that were as cheap and quick to build as possible.  We call this principle manufacturing - the idea is that you could make a robot as easily as you could print a Word document.  We started by looking at origami because origami can produce a wide range of structures and devices.  But at the same time, producing flat sheets is very inexpensive.  And so, you can print your inexpensive flat sheet and then fold it up into the desired machine.  However, we found the limiting factor here, was the time it took to actually fold these machines into place.  For our experienced users, it will take about an hour for our first robotic designs to be folded up.  So, we wanted to find a way to automate that process and make robots fold themselves.

Graihagh -   How long did they take to fold?

Sam -   This robot takes 4 minutes to fold.

Graihagh -   And how exactly does it work?  How does it fold?

Sam -   So, along each fold, we have what's called a hinge.  The entire composite consists of two layers of shape memory polymers, which is sold as a child's toy called 'shrinky dinks'.  And this toy, once heated to a certain temperature, about 200 degrees farenheit or 100 degrees Celsius shrinks by 50% and we bond this to two sheets of paper.  So, when the shape memory polymer shrinks, it pulls on the paper, causing it to fold over at these hinges.  And we trigger this folding through heated resistive circuits and we supply these circuits with electricity.  It heats up that area, causing the shape memory polymer to shrink and pull along the paper, causing it to fold.

Graihagh -   So, when it's heated, it shrinks.  Does that mean you end up with a robot that's much, much smaller than when you first started out?

Sam -   Not quite.  So, the natural mechanism of this shape memory polymer is to shrink, but once we bond it to the paper, it keeps it from shrinking completely.  Instead what it does is pull on it, almost similar to your muscle in your arm.  The muscle itself only shrinks, but because it's attached to two sides, your forearm and your upper arm, it causes the whole arm to bend instead.

Graihagh -   What uses could it have in the future?

Sam -   In addition to our idea of making robots quickly and cheaply, there's a lot of opportunities for building things where humans can't go.  We could use it for building structures in disaster zones or sending in rescue robots.  Personally, I like the idea of sending up a ream of flat sheets into space where they could turn themselves into satellites.

Graihagh -   So, what's the next generation of these origami robots?  What are they going to look like?

Sam -   Well, we're trying to do two things and effectively, expand the range of what we can build, both changing the geometries and the scales, as well as changing how we create the self-folding.  On the scales, I'll actually be presenting in a couple of weeks, unfolding simple objects that are ten times as small.  At that scale, there's a whole different set of challenges but we use different materials.  Instead of paper, we use aluminium and instead of 'shrinky dinks', we use heat shrink wrap, just like the kind you'd find in a supermarket.

Graihagh -   And why are you trying to build something smaller and smaller, and smaller?  Do you have an application in mind?

Sam -   Well practically, we think it might be useful for building tiny robots.  We've actually done other folding-inspired research before in our lab.  We called it pop-up book MEMS where we could build centimetre-scale robots from multiple sheets that pop-up into their final form.  And so, I think we can combine self-folding with these pop-up geometries.  But it's also an academic question because, theoretically, origami can fold anything.  But what does that mean practically?  Can we actually create things that self-fold into anything?

Graihagh -   And - can you?

Sam -   Well, we're working on it, but it's getting better and better everyday.

Grizzly bear

05:22 - Bears can "turn off" diabetes

Obese bears might help further our understanding of how to treat the growing epidemic of type 2 diabetes.

Bears can "turn off" diabetes
with Kevin Corbit, Amgen

New research has shown grizzly bears can become diabetic during their hibernation, and then simply switch it off again in the spring. This could pave the way to a greater understanding of how to treat diabetes, which is on the rise worldwide. Kevin Corbit gave Georgia Mills the bare necessities... 

Kevin -   Diabetes is a disease which is generally characterised as having high levels of sugar in your blood.  Now, there are two types of diabetes.  There's type 1 and that's where your body cannot make the hormone that is responsible for keeping the levels of sugar in your blood normal.  That hormone is called insulin.  And then there's type 2 diabetes in which the body, even though it's either making insulin or receiving insulin through medicine cannot actually respond to that hormone insulin and the blood sugar levels remain high even though the insulin is there.  Type 2 diabetes makes up about 95% of the diabetes and that's increasing.  Traditionally, it is associated with obesity.

Georgia -   So, to try and look at this, why were you looking at bears?

Kevin -   If you just look at a bear that's preparing to go in hibernation, one would probably say that is a very obese animal.  But to be sure, we put the bear through some tests that included to try and measure and waist and yes, that was very comical and indeed, the bears do get quite obese before they go into hibernation.

Georgia -   Is this a bad thing or is this necessary for them to survive the winter?

Kevin -   When it comes to the bears, of course, they're getting obese for a specific reason because they're going to lie down for 5 or 6 months and not eat.  In order to survive that long period of fasting, you have to store a whole bunch of fat.  Now, what's interesting is when they get obese as opposed to what we think about in humans, we found that when the bears are most obese, it's actually, when they become most sensitive to insulin, you can almost think about it as an anti-diabetes.  I think that was the first clue that we had stumbled onto something that was quite different between the bears and humans.

Georgia -   Bears get less diabetic when they get obese.  So, that's the opposite to humans. 

Kevin -   Well, what we think is, one of the other properties of the hormone insulin is, it controls when the body either stores fat or uses fat as a fuel.  So, you can think about this way.  If you were a bear and you are preparing to go into hibernation and you know you're not going to eat for 5 or 6 months, you would want to store every last little molecule fat that you possibly could.  It's kind of like putting a bunch of money away in your savings account when you know there are economic hard times ahead of you.  So, what insulin does is it instructs the body to not breakdown any fat and to store fat instead.  So, if you wanted to store fat, you would want to be as sensitive to insulin as possible.  In other words, you'd want to be very anti-diabetic.  Indeed, that's what we find with the obese bears.  Now, if you go and you enter hibernation, you - in order to survive - have to use the stored fat that you have.  And so, you'd want to prevent the body from responding to insulin.  In other words, you'd want to become diabetic.  In that way, you can breakdown the fat and use it as a fuel source.  Indeed, that's what we think the bears have evolved: this reversible insulin sensitivity or reversible diabetes if you can think about it that way.  They've evolved it to tell them when to store fat and when to use it as a fuel so they can survive hibernation.

Georgia -   So, these bears can turn diabetes off and on, depending on whether they need to process fat or not.  There's no known cure for diabetes at the moment, but could this be starting off on the right track towards one?

Kevin -   I personally started to really rethink how we are treating diabetic humans.  So, without trying to be too provocative, I think by giving diabetics insulin throughout their lives, in the very early stages, this is a good thing because it does indeed lower blood sugar levels in humans.  But in the long term, I'm afraid that we're doing more harm than good.  So, if we take a lesson from the bear, if I would inject you with insulin throughout your life, don't forget that one of the things that insulin does is it instructs your body to store fat and not to break it down.  So, if you take it for a long time, what's going to happen is you're going to store more and more fat.  You can think about a cell and your fat tissue like a balloon.  If you keep injecting that with more and more fat, what happens of course is the balloon gets much bigger, and that is obesity.  If you wanted to live in an ideal world to treat a diabetic, you would want to utilise the existing insulin in their blood and just turn up the ability of the cells to respond to that insulin.  That's what the bears had figured out and we hope we could translate that to humans.

Philae lander - a part of the Rosetta spacecraft

10:55 - Rosetta space probe reaches comet

The comet chaser which has caught up with its quarry after a ten year journey.

Rosetta space probe reaches comet
with Emanuele Cupido, Imperial College London

This week the European Rosetta probe has caught up with the comet it's beenPhilae lander - a part of the Rosetta spacecraft chasing for more than ten years. Rosetta can now finally begin to deepen our understanding of these mystical entities. To find out more, Graihagh Jackson spoke to one of the people who designed the Rosetta probe: Emanuele Cupido from Imperial College London.

Emmanuel -   This week, Rosetta began its real mission.  After 10 years in space, Rosetta has now reached the comet and will start orbiting around it.  So, the real data will start coming down to Earth from the next week onwards.

Graihagh -   And this is the first time it's ever been done, isn't it?

Emmanuel -   That is correct.  There have been other missions which flew past comets whereas Rosetta will be with the comet for a year and a half.  So, this is why Rosetta is very ambitious.  One other aspect is, there's a bunch of people in Germany at the European Space Operation Centre who are in charge of driving the spacecraft while the spacecraft is 400 million kilometres away from Earth while being hit by gas and dust.  In theory, there could be chunks of rock coming off the comet and heating the spacecraft.  So, there are all sorts of challenges with this mission.

Graihagh -   You sort of touched a bit on why Rosetta really is so ambitious, but why is it so important to find out about comets?

Emmanuel -   Comets are perhaps the least studied and understood of celestial bodies because they come and go.  So, it's very difficult to study them from Earth or from space because they are not there most of the time.  you need to go and find them.  On the scientific side, comets brought life to earth in the forms of hydrocarbons perhaps which then started to combine and react with the primordial environment.  So, one of the aims of Rosetta is to go and detect in situ the chemical and physical properties of the comet and find out what a comet is actually made of, whether there are dusts and water, ice or more interesting chemical compounds.

Graihagh -   So, by looking at something like a comet, you can actually tell a bit about the origins of Earth.

Emmanuel -   Well, that will be the ultimate goal.  If indeed, the scientists manage to make a link between what's on the comet and the theories of the origin of life on Earth, that will certainly be probably one of the discoveries of the century.


13:48 - Video games: good or bad?

There's lots of both good and bad press surrounding video games. But what should we believe?

Video games: good or bad?
with Duncan Astle, MRC Cognition and Brain Sciences Unit

We've been hearing a lot in the news recently about the effects video games haveon children. This week, a scientific paper from Oxford says video games could actually be beneficial, even improving cognitive or intellectual ability. However a paper by scientists from Dartmouth College claims there are negative social impacts if children play violent games. So who, and what, should we believe? Ginny Smith went to talk to Duncan Astle, from the Medical Research Council's Cognition and Brain Sciences Unit in Cambridge...

Duncan -   The two studies look at the relationship between how much video game play children engage in and different kinds of psychological and social factors.  And what these two studies have both shown is that there is a significant relationship between how much video game play children engage in and different kinds psychological and social factors.

Ginny -   So, why do you think they found different results?

Duncan -   So, one of the studies has shown that a little bit of game play - so, up to an hour a day- can confer some benefits, relative to playing no games at all.  Playing a moderate amount - so, playing 1 to 3 hours a day has no real effect, and playing more than 3 hours a day - so, what they refer to as heavy game play - has a negative effect.  Some of these games are really taxing of particular cognitive skills.  Like attention, you have to kind of ignore distractions or memory, you have to remember where various things are within the game.  They would argue is that when you play a little bit of the game, you get the kind of cognitive benefits, but you don't spend so long playing the game that you don't experience everything else in the world around you that's important for cognitive development.  But we should also flag up that there are some problems here.  So, one of the issues here is that the relationship may be significant, but it's also often quite small.  So, in one of the studies for example, the effect of the game play actually accounts for 1% of the pro-social hyperactivity measured in these children.

Ginny -   So, in real life, you wouldn't really be able to notice that difference in your child.

Duncan -   Absolutely.  So yes, it'll be hard for us to notice that kind of difference.

Ginny -   So, we've talked a bit about the Oxford study that found this benefit to the one hour of playing, but what about the other one that said that any kind of playing of these violent video games was negative?

Duncan -   So, one of the big differences is that it's different types of games.  In the first study, as far as we can tell, they're including any type of game play whereas in this study, they're meaning very particular adult-like games.  They followed the adolescents over time from around 13 through to around 18.  What they were able to show was that early game play when the individual is around 13, would be predictive of subsequent problems with things like aggression and smoking, and drinking.

Ginny -   Isn't there something else going on here though because I can imagine that a child who is already not very sociable might be drawn to playing video games in their room for hours because they didn't want to go outside and play?  So, how can we tell which way around the relationship is?

Duncan -   That is essentially one of the inherent problems with these kinds of studies.  So, there are essentially what we call correlational studies.  So, they take a natural variability in how much children engage or for how long they engage in playing games and looked at the relationship between that and other kinds of factor.  We can't necessarily from that, infer causation.  So for example, if we took a large group of children and we measured their shoe size and how many words they knew, their vocabulary, we would find a really close relationship between the two.  That's not because learning new words makes your feet grow.  It's simply because the older you get, the bigger your feet become and the more words you learn.  So, we can't necessarily from this infer that playing of video games is causing changes.  It could very well be - as you said - the other way around.

Ginny -   So, you work on what's actually going on in the brain when children practice various different things.  Did these studies fit in with the kind of thing you've been finding?

Duncan -   We're really interested in how children respond to highly structured games and their games attacks cognitive skills like executive functions.  So executive functions are things like attention and memory, and we know they're really important in everyday life and they're really important in the classroom.  They predict really well how well children will learn and how much progress they can make in the classroom.  And so, we're really interested in, if you give children intensive practice, what kind of effect that has on the child's brain?  Our early results suggest that there are some important differences that you can train certain types of simple cognitive skill.  And that does have an impact on the child's brain.


18:39 - School of hard hacks

Children in Britain are going to be taught computer programming in schools as part of the new curriculum in September.

School of hard hacks
with Mark Calleja, The Hack Lab

From September, a new computer curriculum will be taught across the UK.  Computer science teacher, Mark Calleja set up an organisation called HackLab to help schools implement the scheme.  He spoke to Kat Arney about the changes we might be seeing in the curriculum... 

Mark -   As of September, all kids across key stages 1, 2 and 3 are expected to learn a lot of things about computer science in general.  That's ranging from what we know as IT when we were at school which is using Microsoft word, having to navigate your way around Windows.

Kat -   It wasn't Word when I was at school I tell you, basic!

Mark -   I mean, we've gone back now to understand that computer science is actually useful discipline.  It's digital literacy effectively because it's so much different in our world now - digital.  If you can't use them then you are effectively illiterate in a large portion of things, you have to do every day.

Kat -   Now, I would've thought that today's kids didn't need a lot of help to get on their smartphones and their computers.  You can't seem to separate them from their digital devices.  Are there particular things that they'll be learning that aren't just basically how to check Facebook without anyone noticing?

Mark -   We're trying to define the difference between consuming technology and creating with technology.  And so, we're doing a lot of things at the moment with programming, make your own computer games.  But at the same time, learning how to use those things is important as well.  But at the same time, you don't really want students to just be jumping on their iPhone and people saying, "He's really good with computers."  That's not true.  You wouldn't call someone a good cook because they can heat a Tesco ready meal.  The food is there and you can see that the results are there, but they haven't actually done it and they don't understand what is happening.

Kat -   Certainly, when I was a kid, there was a lot about programming in very simple languages and now, things have got simpler, and simpler to use like I can setup a website using Wordpress and it looks fine and then my coder friends tell me, "You're not coding."  So, is that the kind of thing, looking under the hood to actually understand a bit more about how these technologies work?

Mark -   Absolutely, yeah.  I mean, it's important because all of these technologies are the things we use everyday.  Think about your internet banking.  You don't understand how the security system works, but there are people out there who do and they're going to exploit that.  If everybody has a little bit of knowledge then none of us are victims anymore.  If we can to teach the kids how to use the technology, how to protect themselves while using it, they can't be taken advantage of by these people, who are exploiting basically your ignorance.

Kat -   Is it going to cover things like online privacy and all that kind of stuff or is it more sticking with the 'how to use computers'?

Mark -   No.  Online privacy is an enormous part of what we're teaching.  I think it's the most important strand of what we need to teach kids.  It makes a whole quarter of the curriculum as it comes out.  So, one whole strand of the curriculum is called eSafety and how to use the internet responsibly, how to be a good internet citizen.  It talks about cyberbullying.  It talks about how to maintain your privacy online, keep your data safe.

Kat -   Could we be training our kids not to be idiots on YouTube?

Mark -   That would be amazing.  That would be a huge step forward I think, yeah. Understanding that once you put something onto the internet, it never, ever, ever, ever goes away.  It is always there somewhere.

Kat -   Why do you think that now is the time to actually really get computer sciences into the curriculum like this because you know, we have had IT lessons for quite some time?  Why is this change now needed?

Mark -   It's been needed for a long time.  Everyone has sort of woken up to the idea that, "Wow!  We really don't understand half of the way things work today."

Kat -   So, it sounds like we are hopefully going to breed a generation of more tech savvy, more internet savvy children.  What hope for us older people?  Am I going to still have to get kids to help me to use a computer even though I think I can do it now?

Mark -   I hope not.  I mean, at HackLab, we want to do some stuff with grownups too.  We want to have mums and dads come in and say, "Here is what your kid is talking about.  This is what Minecraft is.  This is how you change the parental settings on your iPad so they can't buy a quarter of a million pound digger by accident which is one that actually happened.  Someone thought it was a toy.  They bought a quarter of a million pound Diga on mum's credit card because it linked to her eBay, classic!  So, things like that is what we're trying to avoid.  So, we will be working with grownups too.  So, never fear.

22:44 - The science of combining flavours

Why do foods like lamb and mint sauce go so well together, while other combinations cause us to cringe?

The science of combining flavours
with Sebastian Ahnert, The University of Cambridge

Lamb and mint sauce; cheese and wine; strawberries and cream. Some foods just go together better than others. But why is this? Sebastian Ahnert from the University of Cambridge has been analysing flavours across different food groups, and gave Ginny Smith a taste of what he found... 

Sebastian -   Every food has a unique combination of dozens or hundreds of flavour compounds and these are small molecules that we actually perceive in our nose rather than our mouth.  So in our nose, we have something called the olfactory epithelium and this tissue can differentiate between all of these hundreds of compounds whereas in our mouth, we can only distinguish 5 different tastes.

Ginny -   So, is that why when I've got a really bad cold, everything tastes rubbish?

Sebastian -   Exactly, that's why.

Ginny -   So, you need your nose to be able to actually taste those flavours.  So, if there are hundreds of these compounds, how do you find them and how do you find which ones are important for flavour?

Sebastian -   Well, you can put a food through a machine called GCMS and that will extract all these flavour compounds and tell you how much of each compound there is.  It will tell you the entire spectrum for that given food.

Ginny -   How many of these tend to make up a standard flavour, say a strawberry?  Is there just one strawberry compound or is it a combination of loads of different ones?

Sebastian -   It will be a combination of at least dozens which play an important role.  Actually, a strawberry is an interesting sample because in strawberry, there's no strawberry compound, but strawberry flavour is actually made up of a large number of very different flavours which in themselves don't smell of strawberry.

Ginny -   Fascinating!  It's all really interesting, but what can this kind of be used for?  Why do we need to know this?

Sebastian -   Flavour chemists and flavour scientists use this kind of information to generate artificial flavours.  But the work we were interested in was to actually look at the hypothesis that the chef, Heston Blumenthal put forward and he suggested that ingredients might taste well together if they share flavour compounds.  So, we actually collected a large amount of data on what foods contain what compounds and then drew a network of food ingredients where we linked two ingredients if they share compounds.

Ginny -   Were there any kind of classic combinations that we all know like pork and apple, that came out as actually sharing things on your database?

Sebastian -   Yeah, some of the classics came out and sort of if you look at the network as a whole, you do see that for instance, meat and vegetables are neighbours in the network and that makes sense from our every day experience.  Fruit and alcoholic drinks are neighbours which makes sense if you think about cocktails. But also, a few set of unusual combinations.

Ginny -   Yeah, so onto those unusual combinations.  Before the show, you gave us a few ideas for unusual combinations which we've actually brought along here.  Now Kat, in front of you, there are three little plates.  They're covered over.

Kat -   I'm so excited.

Ginny -   So, I want you to reveal the first one and tell us what you've got on there.

Kat -   This is olives and raspberries.  So, I've got some little slithers of the sort of the yellowy green olives and raspberry.  So, do I just eat them together?

Sebastian -   That would be the idea, yeah.

Kat -   Okay, right here it goes.  I've got raspberry, a bit of olive.

Ginny -   What's it taste like?

Kat -   It's really, really interesting.  It kind of - it doesn't have that really salty kind of flavour of the olive.  It's sort of offset by the sweetness of the raspberries.  It's like a chutney or something like that. It's very rick kind of flavour.

Ginny -   I definitely got raspberry first and then suddenly, the olive kind of kicked in. Why do those two work together?  Sorry, you've got your mouthful now.

Sebastian -   Well, they share a number of flavour compounds.  I mean, these predictions don't always work, one has to say because the data is not perfect.  But I think what this sort of automatic approach can give us is some suggestions for chefs or cooks to look at and try out maybe some new ideas.

Kat -   Yeah, I might put some raspberries in with my olives.  What have we got here?  what's this one?  This is - now, two of my favourite, favourite things in the world.  This is blue cheese and dark chocolate.  I'm going to get it stuck straight in here.

Ginny -   Cheese and chocolate.  I don't know.  It's a difficult one.  I've been reading more recipes recently thatare using dark chocolate as an ingredient, savoury things so often with venison and that sort of thing.

Sebastian -   That's right.  Chocolate has a lot flavour compounds.  It actually goes really well with a lot of things.  There's an American chocolate bar that has bacon in it.

Kat -   I've tried that.  I think it's horried.

Ginny -   I actually made cupcakes with bacon in them for a friend who was obsessed with bacon.  It added something.  I'm not sure if it was an improvement.

Kat -   There are some people who believe everything is improved with bacon.  That's interesting.  The blue cheese and chocolate is interesting.  I don't get any of the sweetness of the chocolate for me.

Sebastian -   It works well with dark chocolate rather than milk chocolate.

Kat -   It's a very savory combination.  Ginny is not looking convinced at all.

Ginny -   I'm not sure. 

Kat -   Papaya and parmesan.  Okay, here it goes.

Ginny -   Now, I can see this working because cheese and fruit is quite a kind of common combination you eat - cheddar with apple or with grapes - that sort of thing quite often.  What's it like, Kat?

Kat -   Mmm... I like that.  That's kind of the classic, sort of sweety, salty thing.

Ginny -   Yeah, that works.

Sebastian - Yes, I think if I remember correctly, actually, there was a dairy cluster in our network which was not far away from the fruit.  We put fruit ingredients.  So, we noticed really at that time that cheese and fruit sit well in the network as well.

Ginny -   Is this something that chefs are actually using to create new recipes?

Sebastian -   Yes.  I started to talk to restaurants and chefs.  They're really interested..

Kat -   This is one that maybe a little bit specialist here.  Ginny hates banana.  It's banana and parsley.  I have to say, I'm not very convinced by the look of this.  Let's go.

Ginny -   I'm afraid I'm not trying that.  I hate bananas.  I'm going to pass on that one.  There's no way I like it even with parsley on.  What do you think, Kat?

Kat -   I think that's quite nice actually.  I think they're quite complimentary.

Ginny -   So, we've had a couple of successes today but a few of you have tweeted us with your weird combinations.  We've got Chris, says, he likes fish fingers and custard.

Kat -   Weirdo!

Ginny -   Neil Brisco says he likes peanut butter and tomato sandwiches.

Kat -   Weird.

Ginny -   Yeah.  Although if you think of peanut butter as being like a satay sauce, you'd eat that with vegetables.  That's quite common.

Kat -   Not really with tomatoes though.

Ginny -   Yeah, maybe not tomatoes.

Sebastian -   The custard and fish fingers sounds very interesting.

Ginny -   We will have to try that one another time.

Kat -   Yeah, maybe not.

Ginny -   Thank you so much for that.  I'm not sure I'm going to thank you for the blue cheese and chocolate one, but olives and raspberries is a revelation.

How a food looks can influence how you think it tastes.

29:35 - Making sense of taste

It's now a well known fact that noses contribute a lot to our sense of flavour, but what about our ears?

Making sense of taste
with Barry Smith, University of London

Our perception of flavour isn't just influenced by our taste buds. Smell, touch and Red Delicious applessound all have a big role to play when we decide how much we might like or dislike a certain dish. Professor Barry Smith gave Kat Arney a small taste of how this can work...

Barry -   So, I'm going to show you something a little bit strange.  I'm opening this packet of sichuan pepper corns.  I'll give you a little one of these.  What I want you to do is just chew on that.  That's a very strong perfume.  If you smell, it's got a...

Kat -   Spicy, yeah.

Barry -   Spicy, but...

Kat -   Peppery kind of... Very aromatic.

Barry -   Very aromatic, very floral.  So, pop that in and start chewing.  I'll tell you a little bit about it.  So, here is another ingredient that we can add to the range of sensations.  It's quite strong but does something start to happen to you?

Kat -   Tingling.  Yeah, really tingly on my tongue, just like...

Barry -   Electricity?

Kat -   Yeah, like a really kind of - not quite the curry hot, but yeah, like something bad is going on.

Barry -   Okay, so that tingling sensation.

Kat -   I'm not sure I like this you know.

Barry -   No, okay.  What's happening is that the active compound in Sichuan pepper is called sanshool and it stimulates the mechano receptors.  It's actually making your tongue vibrate at 50 hertz.

Kat -   [laughing].  My tongue is vibrating.  Certainly, my mouth is watering.

Barry -   Your mouth is watering, yes.  That's the other effect.  When that happens, somehow rather, your saliva glands just run and run and run.  You may need some more water to deal with that.

Kat -   This is not exactly pleasant, I have to say.

Barry -   No.  I've given you a tiny pepper corn and you don't need to have too much of that to have the effect.  But it's interesting that that's vibration.  So, notice that what's actually giving you that sensation, some people say, "Oh, is it burning?"  No, it's not burning.  It is tingling, but its vibration, it's pure vibration.  If you touch it, it can actually stop if you actually got enough fingers on your tongue to hold it, you can still it for a little while.  We can do this better on the lips.  When people have a little bit of it on their lips, they touch the lip, you can still the vibration.

Kat -   Oh yeah.

Barry -   Right, so that's just...

Kat -   Still dribbling after a while there.

Barry -   You're still dribbling, I know.  I may have to talk until you recover.  But this is again just showing you that you've got vibration.  You've got touch, you've got the stinging, burning, tingling, of trigeminal sensation.  You've also got smell.  You've got taste.  So, a huge number of senses are coming together and yet, very often, when we get a complex dish, you think, it's just one thing - the flavour.  So, the brain is putting together a tremendous amount of information and computing it to provide a unified percept, a unified experience of that flavour of something even though we now know it's a very complex fusion of many, many different senses.

Kat -   So, if we think that the taste of something is made up of this very, very complex interplay of our senses, what can we do then to fool our senses or to make our food maybe more exciting or interesting?

Barry -   Yes, this is one of the things that chefs are obviously aware of, is that now they know that the pallet to work on is including not just taste and smell from the food, not just the texture of the food, which is important, but there are other ingredients that they can use including for example sound.  So, one of the strange things is that sound has an impact on how you taste things, on the flavour of things.  But there's also another dimension of tasting we haven't talked about and that is the fact that we get a temporal dynamic when we're tasting.  Tasting is not a single experience.  Tasting is a sequence of experiences of say, a wine entering the mouth and traveling across the tongue, and then swallowing.  When you swallow, that's when you pulse lots of odours up into the epithelium and you get that big hit of flavour.  So, if the tempo and the pace of something traveling across the tongue were to match the tempo of a piece of music then we know the brain is on the lookout for any matches and it probably thinks, "Oh, these are simultaneous or synchronous.  Pay attention to it."

Kat -   So maybe if you were in a wine bar and you're thinking, "Yeah, this wine is really nice" and then you try it at home, it doesn't taste the same.  Could it be because of the atmosphere, maybe the music that's playing there is affecting your perception of the taste?

Barry -   Absolutely, it could be and I always say to people when they choose a really nice bottle of wine in a restaurant and they're looking forward to it, then they have to suffer whatever the duty manager has put on the CD and it may not work.  So, don't like the wine, change the music.  Maybe the music will actually enhance the wine, help you to pick things out.  So, I'm going to try and give you another indication of how sound plays a part in tasting.  Here, I'm going to see whether or not sounds are going to give you clues about whether something is sweet or sour or bitter.  So, I'm going to play you three noises.  I'll play them first and I want you to say which one's sweet, which one's sour, which one's bitter, okay?

Kat -   Okay.

Barry -   So, here we go.  Here's the first sound...

[Piano music]

Kat -   That does sound okay.  I think that's sweet.  I'll go sweet with that.

Barry -   You're right.  That's sweet.  Let's try this one.....sweet, sour or bitter...

[high piano music]

Kat -   I think that's kind of sour, sort of acid drops.

Barry -   That's right.  That's exactly what it is.  And so, the last one must be bitter.  Let me just play that for you.  Here's the last one....

[deep piano music]

Kat -   Yeah, I'll will go with that.

Barry::  So, I thought that was great when you said 'acid drops' because you can see why immediately the sourness, that sort of percussiveness, quick high percussive.  You might think of it as being even sharp.  Notice that when we say sharp, sharp is a feel.  So, see how easy it is for our language to do this cross model comparison.  You're moving from taste to touch.  You're saying, "It tastes, lemon juice, tastes sharp" and of course, sharp's a feel.  But it gives you that feeling then when you're listening to a sound of the percussive ting, ting, ting, ting as opposed to the slower, softer tones of sweetness.  Of course, the acidity receptors on the tongue, they will fire up more quickly and therefore, you'll have that very fast reaction whereas the slow onset of building up to full intensity with the sweetness receptors is different.  But that was an example of how one trial learning without any previous experience, you could sort those sounds quite naturally into sweet, sour and bitter.  It shows you that the brain is already associatively set up to compare sounds to tastes.

Roast turkey dinner

36:41 - Why we feel full

What signals does our gut send our brain once we've eaten enough?

Why we feel full
with Tony Holland, University of Cambridge

Most of us know what it feels like to be full, especially after Christmas dinner.  Our bodies have a few different ways to tell our brains we've had enough to eat. But in some people, this process doesn't work.  Not being able to feel full is a serious problem and a symptom of the genetic disease, Prader-Willi syndrome.  Professor Tony Holland from the University of Cambridge told Ginny Smith how we know when we're full...

Tony -   The body has really developed a number of ways to, if you like, to inform the brain that you've had enough to eat.  So, as food enters the mouth, into the stomach and then is absorbed in the gut, there are really two major processes that are going on that feedback to the brain.  One is, that there are changes in the blood, glucose and insulin. Well they have an effect on satiety, the sense of fullness.  But also, there are other chemicals that are in the blood that actually influence the brain.  The second way that this feedback mechanism is happening is through a nerve called the vagus nerve and the vagus nerve if you like, links the brain and the gut and there are messages in both directions - both the brain telling altering the gut and the gut telling the brain that food has entered the gut and is being absorbed.  So, it's really quite a sophisticated feedback mechanism that helps change us from a sense of hunger to a sense of fullness.

Ginny -   So, what happens if this system goes wrong?

Tony -   The commonest example is severe obesity and where the system doesn't regulate well enough so that you continue to eat when in fact, you've had enough calories that the body requires then of course, you will put on weight.  There are conditions of course where you lose weight too.

Ginny -   So, you work on Prader-Willi syndrome.  Can you tell me a little bit about that?  What exactly is it?

Tony -   Prader-Willi syndrome is a genetic disorder.  It's often referred to as a neurodevelopmental syndrome and by that, what it's meant is that it's really apparent birth.  So, a baby born with Prader-Willi syndrome will be characteristically very, very floppy.  There's a certain irony really here because that baby usually can't feed very well and in fact, often needs assistance very early in childhood to make certain it has enough food. But from about 2, 3, 4 years of age, you begin to see a substantial change.  In fact, the baby and the infant will eat and eat, and eat.  And it's at that stage, severe obesity can arise if people aren't aware that you need to control access to food, you need to limit how much food you give.  That's one of the characteristic features.  There are a number of other features about Prader-Willi syndrome.  They tend to have some learning disabilities.  They are often of short stature because of low growth hormone.  And also, they don't develop sexually normally because of low sex hormones.  And as a psychiatrist, I've also been very interested in the fact that they have often some problem behaviours.  They may have a quite high risk for mood disorder and other mental health problems.

Kat -   Do we know why they eat so much?  Is it that they're always feeling hungry and why is that?

Tony -   These things of course are very difficult to assess because you can't readily get inside someone's brain and decide, determine, what's actually happening.  Our own work would suggest that that is probably the case.  So, both in terms of -if you observe people with Prader-Willi eating and you ask them to rate how hungry or how full they are, or if you want to take now more sophisticated studies using some of the brain imaging techniques, it looks as if that the brain responds to conditions of hunger in much the same way as you or I do.  But in fact, if people with Prader-Willi syndrome eat even substantial amounts of food, the brain doesn't change in the way that it does as it would if we had eaten the same amount of food.  So, it looks as if there is a failure of this feedback mechanism in Prader-Willi syndrome.

Ginny -   So keeping control of the food is a way of stopping them becoming obese, but it doesn't actually solve the problem if they are feeling hungry all the time. Is there anything you can do to change that?

Tony -    that is obviously what I think all of us are working towards. The idea that whether it's mediciation or some other intervention might actually suthis feeling of hunger, and dramatically change the life of people with Prader-Willi syndrome.  But one of the things we tried recently is something called vagus nerve stimulation and we had three people with Prader-Willi syndrome who've had one of these stimulators which is a bit like a cardiac pacemaker inserted.  That then ran for many, many months in the hope that this would reduce the overeating behaviour.

Ginny -   So, you're stimulating that nerve that connects the stomach to the brain, in the hopes that you might be able to change the messages.

Tony -   The reason we thought we should try it is, theoritically, it seemed to us, if you, if you like, stimulated that nerve, you might increase this feeling of fullness. That's perhaps a bit naïve.  However, there is a good data to suggest that when people have vagus nerve stimulation for epilepsy for example and it's an approved treatment for epilepsy then a proportion of people who - particularly those who happen also to be obese, actually lose weight when they're on the vagus nerve stimulator.  Again, this is over months or even years.  So, there is some evidence to suggest that this treatment might actually result in weight loss.

Ginny -   And did it work in your study?

Tony -   Sadly, it didn't really result in very significant weight loss in the three people.  One person in fact put on some weight and someone else lost some weight over time.  However, there was an observation that particularly the parents and two of the three people with Prader-Willi syndrome themselves made.  And that was, that whilst on the vagus nerve stimulator, that many of the other behaviours, particularly the temper outburst reduced dramatically.  Now, these are behaviours that are very debilitating for people with Prader-Willi syndrome.  They're often triggered by change in demands in people's lives.  But they can be quite serious and sometimes lasts at their worse, for hours.  And what the parents were telling us - that outbursts essentially stopped.

Ginny -   So, if this was actually affecting their mood, would it be worth trying for perhaps other mood disorders - anxiety, depression, that sort of thing?

Tony -   Yes, vagus nerve stimulation is used for treatment resistant depression.  So, it is approved in many parts of the world for that.  We don't actually think that it's having its effects through mood in Prader-Willi syndrome although we can't be certain about that.  We think that it's having its effect through somehow increasing resilience if you like, reducing the arousal that people with Prader-Willi syndrome experience when there's something in the environment that they don't like.  So you and I, by and large, we're able to contain ourselves under those circumstances, but for someone with Prader-Willi syndrome, they have really quite a low threshold for and they might lose it under those occasions.  Maybe it's just raising that threshold in some way.

Cartoon of the brain

43:47 - Food and mood

The microbes inside of our stomachs may be affecting our mood, and even behaviour...

Food and mood
with Emeran Mayer, University of California, Los Angeles

It's well known that chocolate has the power to make you happy, but how does food affect your mood? New research shows that stomach-brain communications are complicated, and involve the billions of microbes that live in your stomach. Dr Emeran Mayer from the University of California spoke to Kat Arney about the microbes in our bodies...

Emeran -  The microbes are really present all over our body.  It just happens to be that the highest concentration of them is in our gastrointestinal tract with a gradient from the oesophagus, stomach, small intestine, to the colon where we have the highest concentrations.  The number of these microbes is staggering.  It's up to 100 trillion of these microbes that live with us.  Which is about 10 times more microbial cells than we have human cells and as I say, the majority of them lives in our large intestine.

Kat -   What are they doing there?  Are they just helping us to digest our food or are they doing other things too?

Emeran -   It's a difficult question.  They certainly do help us digest our food and harvest metabolites that we would normally lose because we don't have the enzymes to breakdown certain aspects of food like all the fibre components of food.  The bacteria, they thrive on those things that our human intestine cannot digest properly.  So, they harvest a certain percentage of the food that we take in and change it into metabolites that's in our colon can absorb and we can take advantage of these extra calories.  So, that's the simplest way to explain what they're doing.  That's probably the reason why they have been living with the host for millions of years.  You can even go back to grasshoppers, bees, and other more primitive organisms that have their own gut microbiome.

Kat -   We sort of hear a lot about the gut microbiome nowadays.  It's very trendy.  It's very sexy almost - if your gut bacteria can be sexy.  But thinking about how they may have more roles in our overall health and perhaps in our mood as well, what do we know about that?

Emeran - Their main function has to do with our metabolism and harvesting calories, people have speculated and this is clearly at a stage a speculation, that they have developed capabilities of hacking into our own communication systems that are very elaborate that link our gastrointestinal tract with the brain and other organs, with the liver, with the immune system.  And that they have developed this ability to hack into those human programmes and modify them according to their own needs.

Kat -   So, our gut bacteria could basically be controlling us.

Emeran -   So, some people have said, you know, we're basically just a vessel for the microbes to move around and optimise their own survival and thriving.  So, one example is that they may have the ability to hijack our dopamine system, the reward system that drives us to do a lot of things, our motivation.  But particularly, it plays a role in food intake.  That may be one of the reasons that they play a role in the obesity epidemic. There are studies that the microbes not only contribute to obesisty because of the mechanism of rescuing 10% of what we eat but normally not be absorbed.  But also, that they have the ability of changing the food preference and ingestive behaviour.  One example is, in a so-called knockout mouse, the genetically engineered mouse that lacks a certain receptor in the gut.  That mouse is obese and it's characterised by having an increased food intake.  So, these mice are hyperphagic - they always want to eat.  And if you take the faeces, the microbes in the large intestine and transplant them into normal mice, these normal mice will now eat a lot more foods.  So somehow, we don't know the mechanism, but it points towards the possibility that they can really connect into some very profound systems in the brain.

Kat -   I mean, as well as being a warning that you probably shouldn't eat pooh from fat people, is this basically, our gut microbes could be telling us what we like, what comforts us, what food that makes us feel good?  Could this explain why for example, people with sort of chronic conditions like IBS, could that be affecting their mood through their gut bacteria?

Emeran -   The experimental data in humans is very sparce, so we really have - we're forced to speculate.  However, there's very intriguing observations in the variety of animal models that would suggest that, for example, the weight loss after bariatric surgery for example that is pretty sudden...

Kat -   It's stomach stapling basically.

Emeran -   Yeah, various forms of stomach stapling and modifications that initial substantial drop in food intake is already too had change in the food preferences.  We know that gastric operations are associated with major changes in the gut microbiome.  So again, an indirect but intriguing speculation...

A pair of headphones

49:23 - Why can't I concentrate if I can hear music?

We get to the bottom of why music helps some of us work, while is a complete distraction to others.

Why can't I concentrate if I can hear music?

Ian - It's not just your age that will affect this. Your personality, musical preference, the particular task, your personal experiences or how musical you are, all probably have an effect on how much music can distract you.

When we encounter music in the background as opposed to actively listening to it, it may affect us in two ways. It may affect our emotional state, either positively or negatively, helping us to work better or causing us to work worse; or it may affect our concentration by inadvertently capturing our attention, diverting it away from the task at hand.

On the other hand, it may have no effect at all. A group of German researchers looked at the many studies that have been done and they report that background music disturbs the reading process with some small detrimental effects on memory, but has a positive impact and emotional reactions and improved achievement in sports.

But, as they point out, it's very difficult to compare results across studies because the methods and the experimental participants varied so much from study to study.

It's reasonable to think that, for some people, background music provides a means of giving a self-selected sonic texture to their surroundings, marking off a private space within which they can focus on what they're doing. Without background music, these people would be more easily distracted from the tasks that they're undertaking.

For other people, background music itself would constitute too much of a distraction, diverting attention away from the task at hand. For both types of people however, the important factor would be whether or not they liked and selected the music.

Music that is present without your consent is always more like it cause negative effects and impact on your performance on the task at hand. In other words, if your neighbour is playing music that you don't like, and you have no immediate influence over them, it's much more like they destroy your ability to do your work than if you yourself have chosen the music that's playing.


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