Episode 73 | Mar 14, 2024

The Power of Smell: How Food Aromas Shape Your Eating Habits, With Rachel Herz

Everyone loves the delicious smells of baking bread or cookies, gardens in the springtime, or fresh fruit ready to eat. But did you know that those smells have a significant impact on your eating habits? This week, Dr. Sandi welcomes Rachel Herz, a neuroscientist and expert on the psychological science of scents and smells.

Without a sense of smell, food wouldn’t be the same. According to Herz, aroma has such an impact on our taste that it can truly make a difference in the enjoyment of eating. Sure, the mouth can taste the five different flavors (salt, sour, sweet, bitter, and umami) and feel the texture of the food, but the smell gives us complex flavors and tastes that draw us to our favorite foods. Moreover, food scents drive cravings and hunger, influencing our food decisions in ways you might not believe.

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Episode Transcript

Dr. Sandi: Welcome to “Health Coach Talk.” My guest today is Rachel Herz. She is a neuroscientist, and she happens to be the world’s leading expert on the psychological science of smell. She has been conducting research in this rea and so many others on senses, emotions, perception, motivated behavior and cognition since 1990. She has given TEDx Talks, published over 100 original research articles to date. She’s won numerous awards. She’s on the faculty of Brown University. She is a consultant to various aroma chemical industries, and she is an expert in this area. She has written several books. What we are going to be talking today is her book about “Why You Eat What You Eat.” So, welcome. And that book has been ranked among the best food books of 2018 by the Smithsonian and The New Yorker. So, those ar quite accomplishments, and it’s a pleasure to be talking with you, Rachel.

Rachel: Thank you so much, Sandi. It’s a pleasure to be on your show.

Dr. Sandi: So, what attracted me to this area and why I really wanted to speak with you is because we talk in functional medicine and in health coaching about why we eat. We often talk about emotional eating. We talk about hormones regulating why we are eating at a particular time, our hunger perceptions, for example.

But you have talked about something that I think is fascinating and needs to be really discussed more and that health coaches who are listening can use to help their clients have a better relationship to food, why they’re eating, what they’re eating, when they’re eating, how they’re eating. So, let’s dig in and talk about aroma, your area of expertise. How does that affect our perception of flavor? Let’s start there.

Rachel: Okay, well, for one, aroma is almost everything to do with flavor. So, taste,, in fact, is a very simple sensory system. It’s really only the five basic sensations of salt, sour, sweet, bitter, and umami. You can possibly get into arguing about whether a lack of taste is a taste or not and so forth. But basically it’s these very simple sensory perceptions based on the chemicals that are dissolving in saliva in our mouth. And everything else that we experience when we are eating come from the aroma of the food that we are chewing at the same time as we are tasting the salty, tasting the sweet, and so forth.

So, for example, if you could not smell and you bit into a delicious-looking piece of chocolate layer cake, all you would taste is sweet. Now, you would also get there other oral sensations, so there’s fatiness and creaminess. You’d be able to feel that. Or, if we were eating something spicy, you will be able to get, like, that burning sensation, which has not to do with smell. But you would not get any of that chocolate pleasure, any of that chocolate aroma.

Likewise, biting into a piece of pizza, you would be tasting salt. You would be getting the oiliness and so forth from cheese and so forth, but you would not get anything else. You would get some texture and potentially, depending upon what the toppings were, but you would not get any other perception other than the basic taste sensation and some of the sensories of the somatosensory like the feel of the food.

Everything else comes from smell. And this is because when we eat, we are breathing. And this is actually critical for our perception of flavor because breathing is where the aromatic molecules that are floating through that air that get into our nose come from. And they come from both inhaling through our nostrils and also getting up into the area that is doing the sensing, which is right here, from the back of the mouth.

We have an open airway system between our nose and our mouth, and anyone who’s ever been laughing while they’ve had food in their mouth and all of a sudden…or liquid and have it come out their nose knows this very well maybe when you were a kid or, if you have a really stuffed up nose and you feel food doesn’t taste right, it’s because that passage is being blocked by mucus.

But normally when we’re breathing and we’re eating, we’re inhaling while we have food in our mouth and then we’re exhaling also with the food in our mouth and that is sweeping the air with the aromatic molecules in it from our mouth through our nose in this, kind of, circle, which then activates the same receptors that are being activated when you’re sniffing a rose and so forth.

But because it’s happening at the very same time as something that we’re chewing on in our mouth and because it seems like it’s coming from our mouth, we always say taste when we’re referring to everything that’s going on here when really the majority of it is actually coming from our nose and it’s our brain putting that together that makes flavor.

Dr. Sandi: So, we should be thinking smell if our taste is off or rather than just focusing on taste. If something doesn’t taste good, we should look to the root cause, which is what we do in functional medicine, and that could be altered smell.

Rachel: Yeah, most likely when people say they’ve lost their sense of their taste or there’s something wrong with their sense of taste, not 100% of the time but nearly 100% of the time, what’s really gone on is something is going wrong with their sense of smell. And a lot of things have gone awry with people’s sense of smell as a function of COVID, either losing their sense of smell or also having, which is even potentially more disturbing, what’s called parosmia which is altered smell perception. So, instead of biting into that chocolate cake and expecting it to be really good, you’re getting flavor, but it’s really nasty. So, maybe it’s like, kind of, rotten eggs or it seems burnt or all kinds of other, sort of, distorted perceptions. And then people say, “Oh, the food tastes terrible,” but it’s not the taste per se. It’s what’s going on with your sense of smell, and there are various things that can be done to help that.

Dr. Sandi: So, I’ve heard that, as we get older, elderly populations, our sense of smell diminishes. It might be a sign of early onset dementia or other neurodegenerative conditions associated with that. And I remember my mother who, in the last few years of her life, she had also… And she would only want these ramen noodles that were so salty and nothing else tasted… She had no taste left probably. It was because of her sense of smell.

Rachel: Well, she did have taste. She had the ability to taste salt.

Dr. Sandi: To taste sale, yeah.

Rachel: And as Michael Moss pointed out, salt, sugar, fat, those are extremely positive sensations for us because they are actually signals for critical macronutrients that we need. Sweetness is signaling carbohydrates. They’re the easiest form of convertible energy. So, wanting sugar is very positive from the point of view of our survival. Salt is typically correlated with protein. And fat is the best, sort of, macronutrient if you want high calories. So, we’re hardwired to really love those sensations. And if we’re missing aroma, we’re going to go for foods that are high in those sensations.

And so someone who has lost their sense of smell, and as you point out, often decades before or at least a decade before the onset of things like Alzheimer’s and Parkinson’s disease, someone can be finding that they either can’t name what very familiar scents are like someone who likes to cook a lot, and they pick up the cinnamon, and they smell it, and they don’t see the label there like, “What is this? What is this?” or they can’t actually even smell it. And these could be warning signs that even occur in people’s 40s if this is where they’re going. So, if someone is in their 40s and they start having these kinds of problems, it’s really important to get checked out because the sooner that these things can be discovered, the sooner treatment can be begun, and the better the long-term prognosis.

But also, as you said, I mean, Alzheimer’s disease specifically, especially as it progresses, destroys the sense of smell and also for many of us, although again it’s very different person to person like everything. So, like, people’s hearing can be great if they’re in their 80s or not. People’s eyesight likewise and the sense of smell as well. Typically as we get older, it gets worse, but there are also things you can do to help fight against that. One of them is smell training.

But definitely as… I wish we can talk about it in a second, but definitely, as you just pointed out, what people tend to do with food… And typically smell loss is very gradual. It’s happening in the background. People aren’t really realizing this is happening. And so what they do with food is they augment the condiments. So, adding more salt to what they’re eating to, kind of, boost the sensation. Really they’re just boosting the saltiness. Or, a better potential solution is adding spices. So, if you can add more spice and if you tolerate spice, then that can give you more sensation without potentially having the health consequences that adding a lot of sugar or adding a lot of salt to food might produce.

Dr. Sandi: So, you’ve mentioned touching on getting that aroma back or your sense of smell, how to train that. can you comment on ways to do it? I heard essential oils might be helpful sniffing…

Rachel: Well, it doesn’t actually matter whether it’s an essential oil or something that came out of the cupboard in your kitchen. So, basically what you want to do is just actively stimulate your sense of smell while you’re also actively thinking about what you’re smelling. And this can be very effective for people who’ve had smell loss from a viral infection, particularly if it’s within the first year of this loss.

So, COVID is a classic case in point, but even before COVID, there were various upper respiratory tract infections that could cause smell loss. And also just for everyone with a healthy sense of smell, as we get older, just, kind of, a daily practice, is to exercise your nose. So, all you need to do this, to start off with, is basically four familiar scents that are different from each other. So, just like off the top of my head, just thinking about what you might have at home, you could think of peanut butter, you know, your favorite shampoo, maybe, like, a spice that you like. So, for example, it could be cinnamon and maybe something else in your kitchen like coffee or maybe something else from your, you know, personal care products like sun tan lotion. Whatever the case is.

So, there are four distinctive scents, and you just sniff. And even if you can’t smell anything, so if you’re doing this and you have smell loss, what I want you to do is think about, “Okay, this is peanut butter. I know it’s peanut butter. Why did I like to eat peanut butter? What does it mean for me?” And have some, sort of, thinking going on while you’re sniffing it even if you can’t do any, you know, pick it up. And then do that with each of the scents that you have, and try to do that at least two or three times a day, if you can. It’s only going to take, like, a couple of minutes, but it is sometimes hard for people to get motivated to do it especially if they’re not able to smell anything and they feel like, “This is really frustrating. What am I doing?” But it can be really effective over time for people who have had this, sort of, viral smell loss, especially if it’s early on, and for everyone just like as a daily practice. Get your four scents out and sniff them. And what you should is, after about three months or four months or so, get another set of four scents.

So, you really don’t need to go and spend any money specifically on this. Certainly, you can. I mean, I’m not saying don’t. Sometimes it’s easier if you have, like, the scent in front of you and then you don’t have to worry about trying to find things in your home. But really all you need are four different smells and to actively work at sniffing them just for a couple seconds each while thinking about it several times a day. And that exercise actually will really help stimulate the neurons to keep on working well and also making the connection between your brain and what you’re smelling and making that connection stronger, too, which has good benefits just for overall cognition, not just for smell and cognition but really overall brain function.

Dr. Sandi: Wow, I love that. And it’s something that health coaches can definitely suggest to their clients. Rachel, can you comment on the connection between aroma, food, and appetite? How are they related?

Rachel: Well, I think we all know very well that especially if we’re hungry and we smell something that’s tasty to us, and even if we’re not that hungry but we’re suddenly reminded, wouldn’t it be nice to eat something like the smell of baking cookies or the smell of some other kind of food wafting from a restaurant, or even, you know, walking by a coffee shop and you smell the aromas of the coffee. It’s like, hey, this is a tremendously positive trigger for, “Oh, let me go and get some.” And this is like I said, if you’re totally saturated with, “I just had all the coffee I could ever want, or I just ate so much chocolate, I’m sick.” If you smell some chocolate, it’s not going to have that, sort of, alluring effect. But even if we’re not really hungry, and we’re just sort of, you know, in the in-between state, and we get a whiff of one of these aromas that’s really positive, we’re going to be directed to it.

Now, the really interesting thing, and this was shown in a series of studies fairly recently, is that if we’re exposed to these, sort of, indulgent, delicious aromas for at least two minutes and we don’t want to go too much longer than two minutes because we can then potentially stop being able to smell these smells well, so two minutes is, kind of, the sweet spot of you’re exposed to baking cookies for two minutes, you can kind of actually get the pleasure of the cookies without then going to eat the cookies. And there were several studies that were done, which show that people actually made more healthy food choice purchases after they either smelled cookies or pizza compared to if they smelled apples or strawberries. Now, this was for being exposed for two minutes. And interestingly, in the two-minute exposure, if you’re exposed to strawberries, you then pick more indulgent food as opposed to, like, going for fruits. However, if you’re only exposed to these scents for let’s say 30 seconds or less, you actually are then going to be driven towards the food. So, if you’re smelling cookies for 20 seconds, it’s like, “Okay, I want cookies.” If you’re smelling strawberries for 20 seconds, I want strawberries. So, there’s this interesting, kind of, crossover between the length of time we’re exposed and whether or not it gives us that satisfaction or maybe makes us, “Okay, now I’ve had my healthy food. Now I want something indulgent,” versus a brief exposure, which doesn’t just make us want to go towards the food source.

Dr. Sandi: That’s fascinating. Wow, I know we call that the Cinnabon effect. You’re walking in the mall. You have no desire for eating Cinnabon. All of a sudden, oh, that smells really good and now you’re drawn to it. So, marketing advertisers know this really, really well.

Rachel: Yeah, but they have to be careful because if you’re standing in line at Cinnabon for more than two minutes, by the time you get to the counter, you could be like, “Well, I don’t know,” or, like, “What’s another option here besides this?” So, there is this sort of tricky point between getting you and then saturating you basically or making you feel satisfied that you’ve had your treat without actually having to eat it.

So, the sort of trick here, from a coaching perspective, I think, could be if someone is craving an indulgent food and they’re not actually really hungry is to, you know, smell those cookies for 2 minutes and then see whether or not you actually still want to eat the cookie or maybe you’d rather have an apple or some carrots or maybe even nothing at that point.

Dr. Sandi: Good strategy. Well, thank you for that. So, let’s turn to social situations, which are fraught with… Many people have so many issues being in a social situation affecting what they’re eating and how much they’re eating.

Rachel: Yeah, so this is actually…everyone knows the situation of being with other people and trying to curb your enthusiasm for what you’re consuming. And there’s two difficulties here. One is that we’re distracted because we’re in conversation. We’re in this, kind of, social environment. So, we’re not actually paying attention to how much we’re consuming. So, food is in front of us. We’re picking it up off the table. We’re picking it off our plate and we’re eating it. And we’re not even really even processing that we’re consuming it.

And actually the same thing can happen if we’re by ourselves and also distracted, so watching television while eating, working on the computer while eating. All of these are bad for leading to overconsumption because we don’t realize that we’ve consumed it. So, I look over and I’m like, “How is that popcorn bowl empty?” I don’t even know that I ate it because I was just sticking my hand in while I was doing something else.

So, in social situations, we have the, sort of, danger of distraction. We also have, sort of, this group effect, which basically augments how much we eat. And it’s been shown that the more people we eat with, the more we eat. And, sort of, a factorial dimension like two people you eat more with, four people you eat even more than that, six people you’re going to eat even more. So, the Thanksgiving table has all kinds of problems when it comes to overindulgence. One, we have a big group. We have tons of different foods, so we’re going to be sampling everything that we have, and we also have the distraction of all the conversation.

So, what we want to try to do, when we’re in a big group, is to try to bring our focus back to when we’re eating to pay attention to what we’re eating. And this is, kind of, my bottom line, sort of, if you want to distill the sort of message that I try to tell people the most about this, is that literally mindfulness, and I personally don’t really like the term mindfulness but literally paying attention to the experience of eating gives everything that we want to it.

So, first of all, when we’re paying attention, you actually smell and taste the food more. So, you’re literally getting more sensory experience. You’re getting more pleasure from what you’re consuming, and we actually feel fuller sooner. So, anything that you can ever do while you’re consuming to bring your focus to eating is going to make that eating experience more pleasurable, more satisfying, and you’re going to be able to limit how much you’re consuming better.

Dr. Sandi: Well, that’s so important. And at the time that we are recording, the Super Bowl is coming up and that is ripe for just making poor decisions because the type of food that is out, there might be a crowd, and that is going to be perhaps very challenging for you.

Rachel: Well, you know, what else is really interesting about the Super Bowl is in fact, there were some studies done literally looking at how fans ate after football games and in particular when fans were super committed to their team, like really, you know, fanatics and when there was a really intense game and particularly like an occasion like the Super Bowl.

So, whoever is really supporting the team that loses, what I want to caution about is how you eat on Monday. Not so much how you eat on Sunday at the Super Bowl party because everybody’s eating a lot. But what turns out is that fans whose team lost and are really dedicated actually eat a lot more indulgent, like, sort of, high-calorie junk food on Monday than the team supporters, if your team won. Actually, people whose team one tend to feel like all the high, endorphins and everything else from that victory, that, sort of, vicarious victory and actually eat less and eat more healthily. Whereas, the losing team are drowning their sorrows, even inadvertently, like going for pleasure in comfort food.

Dr. Sandi: Wow, that’s just startling. So, something to absolutely pay attention to. And I think the key words are pay attention. I know I am so guilty. I still do or I’ll work through lunch or I’ll be looking at emails or anything that will be… reading a newspaper at the same time. And so having to have that dedicated time. And I eat so much less and pay so much more attention to taste. I don’t remember who said it. There was a famous quote about the letters in the first morsel in that first bite.

Rachel: Yeah, exactly. To that point, another, sort of, like piece of advice is that paying attention to the pleasure that you’re experiencing while you’re eating something. So, I always say do not deny yourself anything, but determine when the balance is shifting between real pleasure and just okay or maybe not even so much. So, you have that piece of chocolate cake. You really want it. Please eat it. However, you don’t necessarily have to eat a lot of it, and you can stop before even the slice is done. So, you assess how fantastic it is for the first bite. Yes. Second bite. Third bite. Maybe by the fourth bite, it’s losing its wham. And at that point, you say, “You know what? I’m not hungry. I am not getting the real pzazz out of this anymore. I can stop.” And that’s okay. Maybe put it in the refrigerator, eat the rest tomorrow, whatever the case might be.

So, I think, you know, we live in this very privileged experience of food being everywhere, often not healthy food. And actually, for people who don’t have as good of an income or social net, often the food is worse for you but typically tastes better and so at least superficially. And so this is also where we have to be careful because, you know, both on the point of view of, “I’m dealing with a really stressful existence, so I want to be comforted by food, and also I’m living in a situation where I don’t have access to very high-quality and potentially more expensive food, and so I’m resorting often to eating less healthily for various reasons.” And why it’s really important to give people, you know, big produce sections, regardless of where the supermarket is and even more so in places where there is a lower economic, sort of, population. So, in any case, it’s again, sort of pushing the fruits and vegetables but also being really aware of what your environment is and how that might be guiding you inadvertently to be eating foods, which aren’t as healthy for you.

Dr. Sandi: Oh, absolutely. And many years ago when I was in my 20s, I really was… I would be categorized as a binge eater. I was so addicted to sugar, and it was nothing for me to eat a pint of ice cream or a bag of cookies. I remember in college just having that relationship with food or just not being able to stop and existing on just sugar all day long.

Now, an apple slice, a carrot tastes so sweet to me, and I savor that taste of sweet potato, purple yam. These are sweet to me. And when I’m with others who are still eating a lot of processed foods with a lot of sugar like they don’t get it and they feel like, yeah, they’re craving those ultra-processed foods with sugar.

Rachel: I mean, but one of the things you just said actually really speaks to this. The less you eat of any taste, so whether it be salty food or sweet food or high-fat food, the more you can perceive those qualities in it when you eat it rather… Compared to eating those foods all the time, you basically wash out on the ability to really pick up those sensory experiences. So, taking yourself away from the food, then, like you said, a carrot tastes sweet. Whereas if I’m eating, you know, candies all day long, a carrot’s not going to taste sweet at all, and I’m hardly even going to be getting the real sweetness from the candy.

So, this is definitely the case. So, when you give yourself, sort of, a sensory diet for whatever, either salt, like I said, sugar or fat, and then you go back to it, it is so much more intense. And then you can say, “Hey, you know what? I really actually prefer a lower dose of whatever it might be. And I can still get actually a lot from it.”

Dr. Sandi: Absolutely. So, let’s turn to our shopping, our decisions that we make every day when we’re in the grocery store, for example. What are some of the factors in terms of the environment that influence our purchasing decisions perhaps?

Rachel: Well, so I mentioned produce before, and it’s interesting how, you know, for example, the sort of layout of grocery stores, when you walk in and there’s produce first, that’s actually something that the grocery store is doing that’s good for you. Because if we go towards the produce first, we’re going to potentially, and especially if it’s a big section, end up buying things in that section. But there’s something else that tends to happen to people, which is really interesting, and it has to do with balancing our virtues with our vices. Unintentionally, unconsciously, we’re kind of always doing this.

So, these were studies that were done when bringing your own reusable bag to the grocery store was, kind of, a novelty and more something that people did when they were feeling virtuous like, “I’m being good for the environment,” and not now where pretty much every state has mandated that, you know, no more thin film bags. You have to bring or you’re going to have to pay and so forth. So, it doesn’t exactly apply today, but when the study was done in California, it definitely applied to, “I am feeling virtuous,” and you can think of other things that you might do that will make you feel virtuous. And it should have the same kind of effect.

And it turned out that people who, in this particular study, which tracked people and was able to see what they bought based on the loyalty cards that they had in this particular grocery store, and then whether or not they brought their own bag, which was also registered at the cash when they were checking out, that people who brought their own bag tended to buy more sweets and treats, you know, potato chips, whatever the case might be than people who did not.

So, the idea being that, even though you brought your own bag and you may have broccoli, you also have more ice cream and more potato chips. And then another thing that relates to, sort of, the way we navigate in a grocery store, it was shown… This was done with radio trackers on shopping carts, that after the produce section, people were most likely to either go to the alcohol section of the grocery store or the ice cream section of the grocery store. And this is when it was not next door. So, like, the wine aisle is not next to the broccoli aisle or the ice cream aisle is not right beside either. You have to, like, traverse to the other side of the store. But again, thinking of that same idea of, “I’ve just put good things into my cart. Now it’s time for a little treat.” And so we’re implicitly always, I think, giving ourselves a little pat on the back when we do these, kind of, good things for us. And we want to sort of reward ourselves with something. And in a grocery store, we’re rewarding ourselves with food. So, this is what we tend to do.

Dr. Sandi: Wow. Well, this is just fascinating. I think we could go on and on. There’s so much research in this area and so much that people are unaware of that influences our food choices, what we eat, how we eat, when we eat, how much we eat. And so, Rachel, I just can’t thank you enough for being our guest today. Your book, would you like to say how people can get it and where can people find you if they want to stay in touch?

Rachel: Well, thank you so much. It’s been a real joy to be on your show. And actually, my book, “Why You Eat What You Eat,” is really all about these kind of hidden factors that are influencing our relationship with food and directing our food choices. So, what we’ve talked about today, kind of, is just the tip of the iceberg, but so many other things that go into sort of sneaking up on us or influencing us. And so you can find “Why You Eat What You Eat” anywhere that sells books. It’s on Amazon. It’s in all the different formats. You know, that’s sort of an easy source. But of course, independent bookstores and wherever you want to buy your book, it should be available. So, please go and explore. And if you want to find me, I have a website, rachelherz.com, and you can contact me through that. There’s a contact page. So, I’d be delighted to speak to anyone who wants to know more.

Dr. Sandi: Well, thank you. And we will post that in the show notes. And again, it has been a delight, very eye-opening. And thank you so much for being with us today.

Rachel: Thank you, Sandi.

Dr. Sandi: Thank you very much.