[Matt] Remember this tongue map?

You probably haven't seen it

since your elementary school days,

but it's been around for decades.

It divides your tongue into distinct sections

that are responsible for interpreting sweet,

sour, bitter, and salty tastes.

It's just wrong and it's doing a disservice

to really the whole population

for disseminating this incorrect information.

So why have generations of students been taught this map

and what else are we getting wrong

about the science of taste?

To find out, we talked to Dr. Robert Margolskee

from the Monell Chemical Senses Center.

We've all seen this famous map.

It's from about a century ago

of the tongue divided into different tastes,

like biter and sweet.

Turns out that is very much wrong.

Can you walk us through why that is not the case

that our tongue is divided

into these neat sections of different tastes?

The taste map was originated by a German researcher

and he came up with his taste map

based on psychological studies of human subjects

for their sensitivity of all different types

of taste qualities, sweet, sour, salty, bitter,

and what he found was that the sensitivity

was not even throughout the tongue.

There was least sensitivity at the very middle of the tongue

and most sensitivity right around the edges.

And he also found relatively small differences

for different taste qualities.

More sweet sensitivity towards the front,

more bitter sensitivity towards the back.

But this has been converted down the years

into a more extreme version of the taste map

that says sweet is at the front of the tongue

and that's where it is, bitter is at the back,

salty and sour at the sides.

And that is totally incorrect.

Okay, so that's wrong.

We have taste buds doing all sorts of things

all over the tongue.

What exactly are those taste buds doing?

Walk us through how taste buds

actually produce what we experience as taste.

At the front of your tongue you find a lot of taste buds

in bump-like structures, and each of those taste buds

has 50 to 100 specialized taste receptor cells

that will respond to different taste qualities.

Some that respond to sweet, some to sour,

other to salty, and others to biter,

and most would add to it amino acid taste,

umami, and in some cases, it looks like they respond

to multiple types of taste qualities.

In other cases, they seem to be very narrowly defined.

When you are tasting things, you perhaps start salivating.

Is this in any way signaling to your stomach

that okay, this is happening,

this is tasting good, prepare for food,

I'm not gonna spit this out, this is coming your way?

Yes, that's exactly right.

So the taste system, even though we take it for granted,

serves a number of important factors in our life.

The most significant one is a decision point.

Is this good for me, will I allow it into my body

with the expectation that it will be nutritious

and a good food source for me?

Or is it potentially poisonous?

Might it be toxic?

What happens, though, when our taste buds get injured?

Does the body have a really rapid response

in bringing them back operationally?

In general, the taste system is pretty robust

and your taste cells can have kind of a lifetime

between one week, two weeks, maybe three weeks,

and then they will regenerate.

Rarely you can lose function to those taste buds

because of damage to a branch of the nerve

that is normally connecting to that taste bud.

So on the opposite end of the spectrum,

we have supertasters.

I personally am not a supertaster, unfortunately,

but what is going on in the bodies

of these folks who have become supertasters?

The supertaster phenotype is an observation

where people are incredibly sensitive

to all types of taste qualities

and it's most obvious with bitter compounds.

The flip side are they're not exactly non-tasters,

but they're very insensitive

and they can hardly detect at all

these chemical compounds that you'll find in broccoli,

Brussels sprouts, and so maybe their favorite vegetable

is broccoli or Brussels sprouts

because they're tasting other compounds

and not these particular bitter compounds

that their supertaster brethren are more sensitive to.

Yeah, I find bitter particularly interesting

because it seems like something

you might be able to adapt to.

Like me personally, I absolutely didn't start drinking beer

until I was 21, obviously,

and I didn't really like it at first.

It was too bitter, but now that I'm 35,

I like it very much.

Is there a way, actually, for the human body

to adapt more to like a taste like bitter?

Younger children tend to be very sensitive to bitter

more than an adult.

It's not genetics, but maybe it's developmental

or epigentic so that at an earlier stage

we're more sensitive to crave sweet and fat,

but with time we can learn that hey,

that bitter stuff is not really bad

and I can associate it with a very positive effect.

For example, those that like beer for the alcohol buzz

or those that like caffeine either from coffee

or tea or other beverages can associate the bitterness

with a pleasant psychological activity,

that little bit of pleasant buzz from the alcohol.

A little bit of pleasant buzz, always.

We also wanted to talk about cilantro,

perhaps the most divisive herb on the planet.

Some people hate it, some people think it tastes great,

some people think it tastes like soap.

I'm not one of those, luckily.

What's going on with the cilantro?

Do we understand the mechanisms as to why some people

hate it and some people don't?

Again, it gets back into your genes.

Some people will have the genetic type

where cilantro has a wonderful flavor.

And if you don't have that particular receptor

or that version of the receptor,

you'll have a different receptor that responds to it

and just detects it as something kind of nasty, unpleasant.

So there's a really interesting

evolutionary story here, right?

You have tastes both for detecting bad things

in our environment, you don't wanna

eat a plant that's poisonous.

If you can taste bitter compounds, you're more likely

to avoid that plant and to survive.

But the other side of this is also

your body being able to anticipate certain foods

and digest them better would theoretically give you

and evolutionary advantage in a way, right?

That's exactly right.

So you're gonna have both positive and negative selection.

That's really interesting and it kinda

makes me think about other creatures out in the world,

how they're tasting things that are going into their body.

So would, say, a carnivore have fewer sweet receptors

or really any at all, because it just hasn't needed those

throughout its evolutionary history?

That's exactly right, and the cat

is a very interesting example of that.

Cats, they live off protein in their diet

and they generally don't eat plants.

And so they don't really need to be able

to detect a sweet plant, a ripe fruit.

They just need to be able

to find the best source of protein.

Cats actually cannot taste sweet.

And so if you give a cat vanilla ice cream

and your cat likes it, the reason they like it

doesn't have to do with the sugar.

They presumably like it because of the fat

or maybe the amino acid umami component of it.

So if we can understand taste better,

is there a way that we might be able

to improve human health when it comes to eating?

There's kind of a disconnect between the way we evolved

under conditions where it was hard to find ripe fruit

or nutritive sources to the current day

where you can just go to a grocery store

and you can buy up as much of whatever you want.

And so our tendency is to overeat,

and especially to overeat sugar

and other calorie-rich foods.

So there are studies ongoing right now at Monell

to see if we can also change people's set point,

their preference for sweet, from a level

where it would be high sugar, high calories

to a level where it would be moderate levels of calories

and that could serve as a diet aid

and, we would hope, reduce the incidence of obesity

and thereby reduce the incidence of diabetes.

Thanks for being with us today and if you excuse me,

I'm gonna go eat a lotta food.

My pleasure, and enjoy your lunch.

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