30 with the VC | Associate Professor Mei Peng on smell, super-tasters, and the complexities of what we eat

30 WITH THE VC — MEI PENG
Source: 30 with the VC - Mei Peng.mp3
Duration: 31:25
Speakers: Grant Robertson and Associate Professor Mei Peng

Transcribed from the supplied audio and lightly edited for punctuation and readability. Timestamps are approximate. Unclear wording is marked in brackets.

[00:00:00] Grant Robertson
Kia ora koutou katoa, nau mai, haere mai. Welcome along to 30 with the VC. I'm Grant Robertson, the Vice-Chancellor of the University of Otago, and this is a series where we talk to University of Otago staff and researchers about the amazing mahi that they do here at Ōtākou Whakaihu Waka, the University of Otago. My guest today is Associate Professor Mei Peng. Welcome along, Mei.

[00:00:22] Mei Peng
Thank you for having me.

[00:00:23] Grant Robertson
Mei is going to talk to us about her work, particularly around the psychology of food. But to start with Mei, you've brought along, as we do at each of these sessions, a special presentation. What have you brought?

[00:00:38] Mei Peng
Firstly, I brought a couple of things. Firstly, I brought my kind of a photo collage of my lab and some activities that we do, just in case you're curious what we do day to day. And another prop I've got is actually something for you to taste.

[00:00:54] Grant Robertson
Oh my goodness.

[00:00:54] Mei Peng
If you're feeling brave today.

[00:00:56] Grant Robertson
You better tell me what it is before I taste it.

[00:00:59] Mei Peng
Well, it is actually just a filter paper being soaked in a compound called PROP. I did test it on many people in this living room, so it is safe. So what I'd like you to do is just put it in your mouth and put it on your tongue, suck it for like a couple of seconds. And if you know, you know.

[00:01:21] Grant Robertson
Maybe I don't have any tastes.

[00:01:22] Mei Peng
You don't taste any bitterness or anything?

[00:01:25] Grant Robertson
Oh, maybe a little. Now I just feel a little.

[00:01:28] Mei Peng
Yeah, okay.That's interesting.

[00:01:29] Grant Robertson
Yeh. Not too much though.

[00:01:32] Mei Peng
Not too much though. So it sounds like you're kind of in the, what do we call, the taster, but not to the non-taster or the super-taster. So it's a simple compound that can tell from people to people how different we can interact with this particular compound. And it has a genetic basis to it. So some people have this particular gene expressed and they can allow them to taste this bitterness. For some people it's extremely bitter actually. But for some other people there's completely nothing.

[00:02:06] Grant Robertson
I'm pretty much in that category. Just a tiny bit of taste. So what's the compound made of? What is it actually?

[00:02:13] Mei Peng
It's a compound called PROP. It's actually, how people discovered this is actually by coincidence. It's actually a medicine that treats thyroid disease. And some people are saying this is too bitter, we have to coat it because it's too bitter. But then some people are saying I taste nothing. But since then this compound has been quite important because it's a way to show that we all taste the things, but we can taste the things very differently.

[00:02:40] Grant Robertson
Oh that's amazing. Oh well, I'm definitely in the, what was I, the low bitter, not the...

[00:02:46] Mei Peng
Taster?

[00:02:47] Grant Robertson
Low taster. What are you? What are you?

[00:02:50] Mei Peng
I'm a super taster.

[00:02:51] Grant Robertson
Are you? So for you, when you taste that, that was really bitter.

[00:02:55] Mei Peng
Extremely bitter, extremely. And this bitterness would linger for about like a prolonged period of time. That's why I particularly didn’t offer to try it today.

[00:03:05] Grant Robertson
Oh, that's really interesting. So you lead the Sensory Neuroscience and Nutrition Laboratory. This is obviously an example of the kind of things you are looking at. But tell me about what's happening in the laboratory on a day-to-day basis.

[00:03:21] Mei Peng
On a day-to-day basis, yeah, of course. So I'm interested in understanding people's eating behaviour. I thought food behaviour is so interesting. It's something we all do multiple times a day. But we make decisions vastly different. Even with ourselves, we could one day prefer something and the other day we prefer something else. I'm interested in this whole complex decision-making model. So ranging from senses, I want to know whether people's sensitivities, how different are we and how that could impact on our food behaviour.

[00:04:02] Mei Peng
But I'm also interested in other factors like our cultural background, some perception about food, and just all sorts of factors that leading our very different decisions for food. And of course, it has a health impact as well. So we also study a particular group of people, try to understand whether the diet has any kind of relationships with the health outcomes as well.

[00:04:33] Grant Robertson
Amazing. How did this start for you? Were you always interested in this or when you began studying did you have a different idea about what you might end up doing?

[00:04:43] Mei Peng
That's a very good question. So I have always studied psychology so I'm curious about people. I think that was my original point but as my study goes I am more interested in people's behaviour. I'm interested in the differences across people and what makes us unique in a way and food actually provides a very good model to study that. So I think my journey just kind of slowly shifted into food and of course being someone who likes food helps as well. So yeah it's naturally come to this way and I think I found more and more about the psychology behind food choices, and I think a lot more research is required.

[00:05:29] Grant Robertson
Absolutely, I mean as you said before it's interesting but it's also important because of the health impacts and what it means for the food that we grow and that we make so it has a very important, you know, it's an important journey to study.

[00:05:47] Mei Peng
Yeah I certainly think so. It has so much, because eating is something we do multiple times a day, it does have health consequences and would affect our health outcomes. So I think that is something we shouldn't overlook when we look at health in general.

[00:06:08] Grant Robertson
I want to ask first about sensory perception and then about the psychology of food. So back to the sensory side, it's interesting the test that you just did. So I was discussing this recently with a friend. I can eat a whole lemon just without any kind of problem whatsoever. For me, it's like eating an orange. I can cut it up and eat it. And I notice that it is a bitter taste or a sharp taste, but I can still eat it. And we were discussing what on earth would mean that I could do that, but my friend, when he was thinking about it, he said, you know, he couldn't, even if you squeezed all the juice out of a lemon, he still wouldn't want to eat it.

[00:06:59] Grant Robertson
Is there something happening in my mouth that is causing that? What are the senses that are making a big difference when we eat food?

[00:07:08] Mei Peng
Well, I would love to have you in my lab and study you.

[00:07:12] Grant Robertson
I know I'm very unusual when I say that.

[00:07:15] Mei Peng
You eat a whole lemon, that's the first time I heard this one.

[00:07:18] Grant Robertson
Is that right?

[00:07:18] Mei Peng
I think so. Yeah, so it's still sour.

[00:07:21] Grant Robertson
Yeah, I can still taste it as sour, but I like the taste.

[00:07:26] Mei Peng
Something you learn from Grant. That's very interesting, but it's a great example to show how our senses could really vary across people. Like some people find something extremely sour, but the other people find it moderately sour. So in your case, I think, yeah.

[00:07:49] Grant Robertson
And is that, those senses in our tongue, I mean, obviously we have taste, what I call taste buds, but is that mainly where we're sensing, or is it being influenced by something else?

[00:08:00] Mei Peng
That's a very good question. So lots of people in general public, we think the tongue is so important, it's where the taste buds are. But we actually got lots of flavour from smell. And we actually got a lot more flavours from smell because with taste, we just have like five types of taste that our taste receptors allow us to perceive. But with smell, there's thousands and thousands of smell in the world. So we got all that flavour from smell, which also makes quite a lot of my research here is about smell, because smell is something we see even more variations across people.

[00:08:45] Mei Peng
So in your lemon case, you probably really enjoy the flavour.

[00:08:48] Grant Robertson
Both the smell and the flavour. I actually read somewhere that the ability to smell lemons has been used in research about dementia and Alzheimer's. That if you that might not be true but I read that if you can no longer smell a lemon that might indicate something.

[00:09:05] Mei Peng
I really I'm so glad you brought this up.

[00:09:07] Grant Robertson
It's not true probably.

[00:09:09] Mei Peng
This is actually one of the research I we are doing at the moment in the lab we're trying to understand more about the relationship between smell and neurodegenerative disease. Smell and neurodegenerative disease have such a close link, but yet it's overlooked sense in health checks and in our health system.

[00:09:37] Grant Robertson
So that is actually something that has been previously looked at, is that there is a relationship between them?

[00:09:43] Mei Peng
Yes, there's definitely a relationship between smell decline and possibility of neurodegenerative disease. So it's definitely a hot topic in the research area of chemosenses and it's promising.

[00:09:57] Grant Robertson
So that's something you'd like to look at more in the laboratory?

[00:10:00] Mei Peng
I would love to.

[00:10:01] Grant Robertson
Oh, very interesting.

[00:10:02] Mei Peng
Just finished writing two grants on that.

[00:10:05] Grant Robertson
Oh well, whoever's out there to fund it, this is a very important area. So that's quite interesting. From your perspective then, because with smell there are so many different smells, that is perhaps more important than the tongue and the taste for food sensory?

[00:10:23] Mei Peng
Definitely. Definitely, from my point of view, definitely. This is actually one of the things I say to students, first year or second year students I teach. I ask this question, of all our five special senses, if you're forced to lose one, I feel the student often feel scared by that question, but which one would you choose? And we see 80% of people would choose to lose smell across the five senses we have because we love our sights, we love hearing. But what I'm trying to convey, the message I'm trying to convey is that smell is very important.

[00:11:07] Mei Peng
It's one of those things that we'll really miss it if we lose it.

[00:11:12] Grant Robertson
It's so interesting, I've never really reflected on how important smell is, but you know you do notice, I notice if I have a cold when you do lose that sense of smell it's very noticeable isn't it?

[00:11:25] Mei Peng
Exactly and during COVID time many people are affected and they made lots of people think oh smell is really important.

[00:11:35] Grant Robertson
Yeah that's so true yeah and COVID was one of the symptoms to notice was losing your sense of smell. Now you said before that moving on from smell, you said before there were five tastes.

[00:11:49] Mei Peng
Taste qualities.

[00:11:50] Grant Robertson
So what are those five?

[00:11:51] Mei Peng
They are, a little test, sweetness, saltiness, sourness, bitterness and umami. Umami is the savoury taste and from a typical thing is MSG, that kind of savoury taste that we get out of meat and cheese, mushrooms, is umami.

[00:12:18] Grant Robertson
So, obviously for an individual person, one of those five might be stronger than the others. So that's one of the things you look at?

[00:12:28] Mei Peng
Exactly, exactly. For instance, we look at people's preference between sweet things and salty things and savoury things. And of course this relationship is, well, I think not many people think about this relationship, but it's really important for our decision making, for what kind of food we like, what kind of snack we would choose, and down to, you know, what kind of dessert or, yeah. So that's one of the aspects that we're looking.

[00:13:03] Grant Robertson
And is one of the senses more common than the others to be strong or is it people even, usually even across the five? How does it work?

[00:13:18] Mei Peng
We have actually done some research on this to look at kind of the relative importance across five senses.

[00:13:26] Grant Robertson
That's what I mean.

[00:13:27] Mei Peng
Yeah, and we have called this multi-sensory fingerprint. We believe some people have more reliance on a particular sense than other senses. So for instance, you know, you would really value smell and eat a whole lemon to get the flavour out of it. But some people could be put off by their sourness and that taste is too strong. So that's a little example to show that this relative importance across those five senses could be very important.

[00:13:58] Grant Robertson
Yeah, that's right. So for you, as your research, where do you see the impact of, for example, the sensory, so you mentioned neurodegenerative as one area. What would be another area where sensitivity would have an impact?

[00:14:15] Mei Peng
Yeah, of course. So there's, I guess one of the things that I'm interested in is looking at a general population, not necessarily, we do do quite a lot of research on neurodegenerative. We also do research with kids to understand neurodevelopmental traits and how the sensory relationships to their experience. But just for the general population, it's also very interesting because all of those sensory character, you know, our sensitivities could shape our everyday food without really knowing it could long-term intake of those foods could lead to some particular health outcomes.

[00:15:06] Mei Peng
So that's also something that we are interested in. Yeah, we're interested in all sorts of people.

[00:15:16] Grant Robertson
It's such a fascinating topic. As we move more towards food psychology, I did want to ask though, can you change the importance of those five senses in your mouth? Is it possible to train yourself to feel one more than the other, or is it something that is just inherent to us and we can't change?

[00:15:42] Mei Peng
I think that's a great question. Certainly there's lots of things, what we could say hardwired, like our genetics. But however, our environment shapes our preference for things as well. So one of the examples that we have is to study sugar reduction. We probably, like, you know, grew up eating certain things or drink or have certain products made us think, you know, Coke should be this sweet, but does it have to be this sweet? Yeah, so one thing we looked into is if we gradually change the exposure or reduce the exposure to sweetness, whether that would change the person's preference.

[00:16:29] Mei Peng
And the results look very promising. They suggest that people will change, depends on the exposures around them. So I think that's one of the, also gives practical benefits or outcomes because then we could potentially look at modifying a person's environment, a food environment, and then lead to better and healthier diet.

[00:16:53] Grant Robertson
Does it work the other way around too? Because I know a number of my friends have tried to make sure that their children are not exposed to sugary drinks when they're young in the hope that when they get a little bit older and they're making more of their own decisions they won't want the sugary drink. Is there anything that is that important for parents? I mean it's obviously good for health and development but is it a way of training yourself not to have it?

[00:17:23] Mei Peng
That's such a good question I mean I certainly hope so.

[00:17:27] Grant Robertson
There's plenty of people doing it.

[00:17:29] Mei Peng
Yeah, being a mum of a six-year-old, I certainly kind of also wonder those questions and also wonder how much we should limit young children from having sweet things or unhealthy food. So I think that's a great question. Certainly the hope is if they don't have the exposure when they're younger, then they possibly will have better food decisions. But of course, you know, they go through teenagers and adolescents, they probably have a suddenly a big exposure.

[00:18:05] Grant Robertson
I know, they might really like it then. Yeah, that's right.

[00:18:09] Grant Robertson
Let's move to talk a little bit more about the psychology of food. And I'm very interested in this personally. I've had a difficult relationship with food my whole life because I've struggled with my weight and I love food. And I sometimes think about the choices that I make with food and how much they're driven by emotion. And I wrote about this in the book that I wrote about, my memoir, where when I was in a very stressful situation during COVID and I was working with the Prime Minister Jacinda Ardern, and when she is stressed she can't eat, and when I am stressed all I want to do is eat.

[00:18:52] Grant Robertson
Are these sorts of emotional relationships with food, is that something that you think is an important influence on people's eating?

[00:19:01] Mei Peng
Absolutely, absolutely. And I think in the research world, we increasingly found out how important emotional related eating is, because lots of our decisions were not just because of senses or our food preference. It's actually because of the emotion that we're experiencing. And as you said, stress, stress eating is such a big topic because it really influences our decisions without us even being aware of it. So emotion has a deep, you know, have a very close relationship to food. I think we're still trying to understand the mechanism behind it.

[00:19:45] Mei Peng
Like when we are stressed, what happens? I'm sure there's a whole lot of things like hormones and reactions to it. But also psychologically that affect us as well because we form habits and the habits itself would make us continue a certain behaviour such as what you said Jacinda not eating and you would like to eat that.

[00:20:15] Grant Robertson
We were the opposite. How do you go about studying that emotional impact? What tools, what methods do you use to understand the emotional impact of eating?

[00:20:25] Mei Peng
That's a great question. So sometimes lots of those researchers still quite rely on self-reported because we know ourselves, so we know how stressed we are. Like for instance right now we're doing a study on campus asking students during exam time. Obviously they— we know they're stressed and then we want to kind of, well, take advantage of the situation and understanding how stress impacts on their food. And we also do physiological testing like we can rely on some physiological measures to understand a person's kind of physiological reactions to food related stimulus.

[00:21:11] Mei Peng
So for instance, we can create a stressful situation, getting them to do a really difficult mathematical questions in front of a computer, increase the stress, but then expose the food stimuli and see their reactions. So all sorts of different methods we could use. The tricky part I think is to understand the complex interactions between those measures as well.

[00:21:42] Grant Robertson
It's interesting to me too when there are certain types of food, especially things like takeaway food, where you often hear people say that 10 minutes after eating fish and chips or something like that, they don't feel that well, yet they still go back. They still go back and purchase it again. What's happening in our brains when we know that a food might not make us feel good or we know it might not be good for us, but we still go back and eat it again and again?

[00:22:14] Mei Peng
Whoa, I wish I could answer that question even just for myself as well. So I think food preference and food wanting actually can be quite different.

[00:22:28] Grant Robertson
Okay.

[00:22:29] Mei Peng
So in the research, we call it liking versus wanting. So liking is something that is very subjective and we know what we like, but wanting is something almost like a craving behaviour. So we just sometimes a certain, as many factors affect a wanting, but in certain situation we just really want that food. So I think the fish and chips example, lots of people have it to satisfy a craving. And what leads to this craving, there are many different factors, there could be cognitive factors because we see something that made us think about this. Or as you said, emotional factors.

[00:23:12] Mei Peng
Or there's, all of a sudden, the body craves for it because of a bio-psychology, right? Like it affects how we want this thing so badly. And even though we know it's not good for us, we didn't feel good last time, but we want it.

[00:23:28] Grant Robertson
Yeah, it's very interesting. Related to that, in 2020, you established ENERGY, the energy neuroscience and eating responses during pregnancy. This was a longitudinal cohort study. Tell me a little bit more about that.

[00:23:45] Mei Peng
Yes.

[00:23:46] Grant Robertson
Because we all know about cravings and pregnancy that people talk about.

[00:23:49] Mei Peng
Exactly, that's exactly what prompted me to get the grant to set up this study as well. I went through pregnancy myself in 2019 and I found it's a really fascinating experience. I mean there are many many different levels but from my research point of view I found the changes of sensory sensitivities very interesting and how they affected my food choices. It's a very different experience so that made me think we need to understand this better because what we eat during pregnancy has such a long-lasting effect for ourselves as wāhine, but also for our children as well.

[00:24:36] Mei Peng
So one thing, for instance, I feel is like during pregnancy, I couldn't smell our fridge. Our fridge at home has this most disgusting smell that I just couldn't open the fridge for even a second, which is a smell just disappeared as soon as my child arrived. So I think that's an example of how our sensitivity do change. And another thing that I found, I heard from lots of women that we took part of our study is food cravings.

[00:25:17] Mei Peng
They start craving for childhood food, like comfort food, and how this— yeah, how they could go out miles to get a particular food that they crave for. So I think that's a very interesting. It gives us a good model to study food related behaviour.

[00:25:38] Grant Robertson
And clearly there must be some connection with hormones in that sense.

[00:25:42] Mei Peng
Exactly, exactly. So that's the part of that brings another angle into this whole puzzle because it's psychology, it's biology, it's their cultural beliefs and there's lots of things coming to play.

[00:25:59] Grant Robertson
So you're going to keep that study going?

[00:26:03] Mei Peng
We are, as we're speaking, we're having something in the lab. One thing that that study leads us to is to look at gestational diabetes. So we're looking at a particular diet, whether that has acute and long-term kind of acute responses in glucose and insulin and how that could link to a gestational diabetes. So we definitely hope to continue on that line of research.

[00:26:34] Grant Robertson
Yeah, it's fascinating because it is, as we've talked and you said, not only do we eat food multiple times a day, but through our life cycle, food is playing a different role as we're children and adults have pregnancy, but also as you said, as you get older. So it must be quite hard to choose what thing to focus on across that life cycle. Is that something you've thought about or are you just, you're doing it as you get older?

[00:27:06] Mei Peng
Is that obvious?

[00:27:08] Grant Robertson
No, but you know.

[00:27:10] Mei Peng
Yeah, yeah. Definitely. I think you're absolutely right. I'm very fortunate to study something that we all do. Anyone does eating. So I think that's given me this opportunity to look at different populations, different subgroups. But I think our focus, of course, is to look at what is most lacking. How can we help? How can we fill either a piece of puzzle or help with the health system looking at the gaps? Yeah.

[00:27:43] Grant Robertson
You have had a Fulbright trip to the United States and you also recently were at the New Zealand Centre at Peking University in Beijing as well. I'm interested to understand what you were looking at at each of those places but first, as part of your work, is there major differences in terms of the psychology of food between different countries like the United States, China and New Zealand?

[00:28:12] Mei Peng
Absolutely, absolutely. Those experiences have made me appreciate how much culture has impact on individuals eating behaviour so much but also as a food system, because like Aotearoa New Zealand, America and China they have really different food models. For instance in China there's— you probably noticed.

[00:28:38] Grant Robertson
I was just there, yes.

[00:28:39] Mei Peng
The amount of Uber Eats— well, their version of Uber Eats— is excessive. During lunchtime and dinnertime, we see on the street, we see so many scooters delivering food. And that system would affect people's eating behaviour and how people choose their food, eat their food, because their choices of food would be on a smartphone. And America would have a very different system as well. People choose their food or prepare their food very differently. The package of the food, the package of the cheese, they're very different from Aotearoa New Zealand.

[00:29:24] Mei Peng
So that gives me this perspective of taking research, thinking about the background and the culture and the place of where the research is conducted.

[00:29:38] Grant Robertson
Yeah that's right because you talked about wants and likes but in addition to that is the environment that you're in as well.

[00:29:47] Mei Peng
Mei, this has been fascinating, but unfortunately we've run out of time. But I want to give you, as I do to everybody, the opportunity: is there one thing that you'd like to say to me as the Vice-Chancellor, as a staff member and a researcher here at the university?

[00:30:04] Mei Peng
There are so many things, but I guess one thing that I wanted to say is my own research career has really benefited from having a multidisciplinary perspective because I learned so much from food science and being an experimental psychologist for training and so I benefit so much from multi-discipline studies and research and everything. So my question for you is what do you think how to help the staff and students to continue that kind of research and studies?

[00:30:42] Grant Robertson
I couldn't agree with you more. That is the future. If we're going to solve big problems and challenges, we need multi-disciplinary teams. I think my job along with other senior staff is to create the funding environment and a supportive environment to bring teams together and get out of all our different silos. So thank you for the reminder, Mei, that I need to do that.

[00:31:04] Mei Peng
Awesome to hear.

[00:31:04] Grant Robertson
And thank you so much for this. It's been fascinating and I'm sure people watching and listening will have learned a lot.

[00:31:09] Mei Peng
Thank you. Thank you so much.

[00:31:11] Grant Robertson
Please do join us again for 30 with the VC as we talk to our researchers and staff at the University of Otago about the amazing work they do. Nō reira, tēnā koutou, tēnā koutou, kia ora koutou katoa.