Here's an illuminating little sensory experiment you can do. Grab any multi-flavor bag of candies
— Skittles would work great. Pour some out on a table in front of you. Close your eyes
and pinch your nose real tight. Air tight. Then reach out and taste one of the candies.
Taste another one, and another one. Are you able to tell any difference between them?
I can't.
This is because a huge proportion of our perception of flavor is actually smell, and this is something
that literally millions of people around the world are finding out the hard way as of this
recording, where we are in the midst of the Covid-19 pandemic.
Many studies show anywhere from a third to a majority of patients are reporting hyposmia
or anosmia — that is, partial or total loss of smell perception.
And here's the scary thing: In 10-20% of those cases, the sense of smell is not immediately
coming back to people, even after their other symptoms have gone away.
Understanding what's going on here can not only help us protect ourselves and potentially
recover — it can also help us all get a better handle on why we perceive food the
way that we do.
Let's go back to the Skittles experiment. Even with my nose pinched, these still taste
like something. Specifically, they taste sweet and a little bit sour. That is their taste.
Their flavors are lemon, apple, strawberry, orange and purple. Or grape, I guess. But
the taste is just sweet, sour and a little salty.
Taste and flavor are words that us normals use interchangeably, but to scientists they
mean pretty distinct things. The scientific word for taste is "gustation," and our gustatory
system consists of receptor cells on the taste buds of our tongue. Mostly the tongue. We
also have a much lower concentration on the inside of our cheeks, on our soft palette
— that's the back of the roof of your mouth — and at the back of your throat around
the food pipe — the upper esophagus and epiglottis.
And what we perceive via our taste buds is pretty simple — the five basic tastes, in
alphabetical order so as to not betray any kind of preference: bitter, salty, sour, sweet
and umami. There is some research indicating the existence of other basic tastes — we
might be able to taste fatiness for example, but that's an area of active scientific debate.
The big five are the widely accepted basic tastes, and we can see some of them right
on the Skittles label.
Sugar and corn syrup — that's sweet. Citric acid — that's sour. And down at the bottom,
one of my favorite ingredients — sodium citrate. That's sour and salty.
The scientific name for smell is olfaction and it works via odorant receptors in our
nasal cavity. In contrast to the handful of types of taste receptors we have, we have
hundreds of types of smell receptors.
Our olfactory system is way more sophisticated than our gustatory system, and smell affects
us on a much more basic level.
"It is the only medium that directly enters the limbic system, where emotions are created."
That's a clip from a terrific French documentary from 2016 all about smell, and it's something
you can watch right now on CuriosityStream, the sponsor of this video, whom I'll now briefly
thank.
In this time of lockdowns and social distancing, I think all of us could use more brain food
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Anyway, when you eat these, you are experiencing them significantly — perhaps even primarily
— through your nose.
Now, I know what you're thinking. You're thinking, Adam — I'm a person of culture. I don't
jam Skittles up my nose — I mean, I did, like, when I was like in college, but it was
college, I mean everybody in college... And now, maybe on my birthday, or maybe New Years
Eve if things get really crazy, but that's it. 363 days of the year it is strictly chew
and swallow, mister. How would this get in my nose?
Well, listen to Dr. Carl Philpott, professor of rhinology & olfactology at the University
of East Anglia.
"When you're eating food, you breath out the air through your nose, and we call that retronasal
olfaction. Because you do it at the same time as tasting on the tongue — which is when
you detect salt, sweet, sour, bitter, and a savory sensations we call umami — those
two things happen in parallel, so most people can't separate those two functions."
And it is the combination of those two senses — smelling and tasting — that we describe,
collectively, as flavor. Those, plus a couple other small things, like the burning sensation
from chiles. They act on pain receptors we have. Stuff like that is considered flavor
too, but mostly flavor = taste + smell.
Taste is just taste. The Skittles folks do claim that there are taste differences between
these. If that's true, it's probably something minor, like the lemon one has a little more
citric acid or something. But manly these different flavors just smell different.
We have a word to describe foods that are particularly defined by their smell, right?
"Aromatic." Spices are aromatic. Herbs are aromatic. Cheese is aromatic. What would a
nice stinky cheese taste like if you couldn't smell?
"Cheese is the most bizarre thing in the world to me. It's like putty. I don't know — because
it doesn't have that kind of, you know, as you bite into it, it kind of like blows up,
I guess."
This right here is Isaac Tagner. He's 22-years-old. He's a student at Grand Valley State University
in Michigan. He's a Vinegar Legate — fan of the channel. He's some kind of personality
on Twitch — not that I really know what that means. And about a month and a half ago,
he was diagnosed with Covid-19. He felt sick, he found out that he'd been exposed to somebody
positive, and it turned out that he was positive.
"I was going to hop in the shower, after like, you know, in the morning. And I was like,
I don't smell bad. Like, you know, I'm gonna take a shower, obviously, but I don't really
smell bad. And then, like, throughout the day, I was like smelling things, like my stick
of deodorant, or like the air freshener in my car, and I was just like, I can't smell
it at all. Nothing's going on here."
Most of us have experienced something like this — when we catch a cold. Your nose fills
up with snot and air can't circulate up there when you eat. Food suddenly tastes way more
bland.
But Covid-related anosmia seems to be different in a couple big ways, the first being that
it comes on really fast. People seem to go from smelling fine to not smelling fine over
the course of like two hours. And then, Dr. Philpott says, it's not because they're congested.
"It's because the virus is actually attacking cells in the top layer of the nose through
a certain type of protein that we have inside the cells, and it's basically causing that
whole cell layer to swell and sort of strangle the smell receptors."
It's kinda like a fighter who takes one in the eye. Her eyeball might be totally fine,
but she's still not gonna see after this because the tissue around her eye is gonna be all
swollen up.
By the way, the particular susceptibility of these upper nasal cells to the 'rona is
one reason why wearing a protective face mask with your nose hanging out is rather like
wearing your pants with your junk hanging out. I mean, I guess there's a point, but
not much of one.
Now, if food is a big part of what you happen to enjoy about being alive, this is where
things start to get particularly scary. The latest research indicates that Covid might
be affecting taste as well as smell.
"The recent bit of work that we did was to actually compare people with common colds
to people with coronavirus, and we say that actually bitter and sweet appear to be taste
functions that were also affected in people with coronavirus, suggesting the virus may
also be affecting those receptors as well as the smell receptors."
And the even scarier thing is that in 10-20% of these cases, so far, people are not getting
their sense of smell back all the way, even after they otherwise feel better. Dr. Philpott
suspects that this might have to do with the virus actually causing damage to the nervous
system, or the brain.
"There is some evidence from previous studies in mice in the previous SARS pandemic that
suggests that coronavirus, in its previous forms, has actually invade the brain and caused
problems centrally."
So if this happens to you, what do you do about it? Well, one option is, adapt — maybe
with a little help from your friends.
"Yeah, like, you know, we leave the apartment and we have the one roommate, who's the cook,
he's constantly, like, doing smell checks, because like, you know, you never know. You
can never be too careful, you know, handing him the gallon of milk, like, Hey, dude, is
this good, like, you know. I didn't really realize how dependent I was on it until I
lost it."
Isaac's roommate is masked, obviously, while he's doing this. He's a culinary student — he
can't be losing his palate.
But all levity aside, what if it really doesn't ever come back — for Isaac, or for the millions
of other people who are in the same boat right now? Well, Dr. Philpott says there may be
treatment options.
"We're doing a trial at the moment to look at some simple interventions with a process
called smell training, which is a rehabilitation technique, and it's very much what people
do in the food and wine and perfume industries — they're kind of training their noses.
In this instance, we're trying to get people to actually reactivate their smell pathways
by working with odors on a daily basis, a couple times a day."
And what does smell-training look like? Well, meet Ross Smith. He's a patient of Dr. Philpott
who spent about half his life not smelling. Obviously it wasn't Covid-19. It was nasal
polyps, which Dr. Philpott was able to address with an operation.
But what if you couldn't walk for 20 years and you got it fixed in an operation. Would
you expect to just be dancing around the next day? No, you would need to kind of learn how
to walk again with physical therapy.
"You get ahold of some essential oils and you just practice each day. You can get different
ones. It's practicing your sense of smell — you're retraining it to recognize, so
— that's pine. I have to keep practicing, OK."
The hypothesis behind this treatment is pretty similar to PT — it's about forging new neural
pathways. Will it work for Covid patients? Obviously, nobody in the world knows that
for sure, but it did work for Smith.
"All food is a great pleasure. It's just the more subtle things, like a boiled egg sandwich,
that you know, you all of a sudden find you can taste."
Could he have picked a more British example?
There's a bunch of links in the description. There's contact info for Fifth Sense — that's
a U.K.-based charity that both Smith and Dr. Philpott work with to help people who've lost
their sense of smell or taste. Also linked is a suicide prevention B-corp that Smith
runs. That's kinda unrelated, or maybe it's not.
People are living with all kinds of extra stress and loneliness and despair right now,
and it certainly would not help things to literally lose your senses, especially smell
— our most primal sense.
"So I can smell things like, hey, I've got little prop out ready for you, Adam. Soap.
I don't know if you have this in the U.S., it's Pears soap. It's — and you know, so
many things from childhood, if — wow, that brings back so many memories. So without the
smell, I've not got the memories."
So protect what you have. Protect your nose — cover it up.