Speaker 1: Welcome to brain Stuff, a production of iHeartRadio, Hey brain Stuff,
Speaker 1: Lauren Vogelbam here. We learn about taste in grade school,
Speaker 1: and out of the five senses, it seems like one
Speaker 1: of the most simple. There are no cones, rods, or lenses.
Speaker 1: There are no timponic membranes or minuscule bones. Yet scientists
Speaker 1: know less about taste than they know about sight and hearing.
Speaker 1: So why is taste so mysterious? To start with? Taste
Speaker 1: is wrapped up in the greater issue of flavor. A
Speaker 1: taste is a chemical sense perceived by the specialized nerve
Speaker 1: receptors that make up our taste buds. Our perception of
Speaker 1: flavor is a fusion of multiple senses, not just taste,
Speaker 1: but also smell, touch, and temperature. In addition to taste buds,
Speaker 1: we have nerve cells throughout our oral and nasal cavities
Speaker 1: that detect molecules that give us a sense of heat, wellness,
Speaker 1: or dryness. For example, you know foods or drinks that
Speaker 1: are spicy, hot, minty, or puckery. It gets even more
Speaker 1: complicated because our interpretation of sensory data is always subjective,
Speaker 1: and flavors are perhaps more subjective than most Some people
Speaker 1: have inherited genetic traits that make certain foods that others
Speaker 1: find pleasant taste disgusting, like cilantro. Others have higher or
Speaker 1: lower concentrations of taste receptors than most of us, and
Speaker 1: as we all know, food tastes different to different people,
Speaker 1: we don't all enjoy the same flavors. Over the past
Speaker 1: couple decades, science has expanded its definition of taste. We
Speaker 1: now understand that we have at least five primary tastes sour, bitter, sweet, salty,
Speaker 1: and savory, with at least four more hypothesized. Science has
Speaker 1: also challenged the tongue map, that biology class staple that
Speaker 1: charts distinct regions of taste and is almost certainly bunk food.
Speaker 1: Scientists have even tampered with taste receptor cells, blocking or
Speaker 1: stimulating them in an effort to cut sugar and salt
Speaker 1: out of foods without sacrificing flavor. Today, let's talk about
Speaker 1: the physiology and psychology of taste and flavor. Taste begins
Speaker 1: with electrical impulses. Sure of food or drink is usually
Speaker 1: involved too, But as we've talked about before on the
Speaker 1: show Sensations, you know our bodily responses to stimuli like pressure, light,
Speaker 1: or chemical composition only become perceptions like touch, vision, or
Speaker 1: taste when they reach the brain. In our mouths and noses,
Speaker 1: certain chemical stimuli activate the chemo receptors responsible for our
Speaker 1: perceptions of taste and smell. Because both our reactions to
Speaker 1: the chemical makeup of an object. The two senses are
Speaker 1: closely related, though the chemo receptors involved with each tend
Speaker 1: to pick up on slightly different ranges of molecules. That's why,
Speaker 1: if you've ever been gunked up with a cold, the
Speaker 1: subtlety of food was probably muted. You weren't getting the
Speaker 1: full picture. In humans, the chema receptors that detect taste
Speaker 1: are called gustatory receptor cells. About fifty of these receptor cells,
Speaker 1: plus some basal and supporting cells, make up a single
Speaker 1: taste bud. The average adult has around ten thousand taste buds,
Speaker 1: and not just on your tongue. Some are spread elsewhere
Speaker 1: throughout your oral cavity. On your tongue, many of your
Speaker 1: taste buds are contained in what's called papilli. These are
Speaker 1: the small bumps that dot the tongue. There are three
Speaker 1: different types, arranging from smaller mushroom shaped bumps on the
Speaker 1: front of the tongue with only a few taste buds each,
Speaker 1: two larger, deep, goblet shaped bumps at the back of
Speaker 1: the tongue with hundreds of taste buds each. The papilli
Speaker 1: help you taste food and drink because they greatly increase
Speaker 1: the surface area of your tongue and therefore the number
Speaker 1: of taste buds that can fit on it. And they
Speaker 1: can help create friction between the tongue and food at
Speaker 1: breaking the food up. And they can help saliva wash
Speaker 1: over food and actually get particles of it to our
Speaker 1: taste buds. Each taste bud is a little bundle set
Speaker 1: into the surface of the tongue or the base of
Speaker 1: a papilla. A taste bud looks a little bit like
Speaker 1: a flower bud. Each of the petals that make it
Speaker 1: up is a gustatory receptor cell. These cells have spindily
Speaker 1: protrusions coming up to the tip of the taste bud
Speaker 1: called gustatory hairs. These taste hairs can brush up against
Speaker 1: bits of food that you eat with the help of
Speaker 1: your saliva. Proteins on the surface of the hairs will
Speaker 1: bind with particular types of molecules and stimulate the sensation
Speaker 1: of taste. The receptor cells are connected to nerve fibers
Speaker 1: that pass on electrical impulses to the gustatory area of
Speaker 1: the cerebral cortex. The brain then interprets the sensations as taste,
Speaker 1: together with other sensations like smell and maybe heat. If
Speaker 1: you just ate a chili pepper, your brain gives you
Speaker 1: a concept of flavor. There are a lot of compounds
Speaker 1: in foods and drinks that give them their nuanced flavors.
Speaker 1: For strawberries, researchers have isolated over three hundred compounds that
Speaker 1: affect our experience of smell and taste. For tomatoes, it's
Speaker 1: over four hundred. Until recently, scientists accepted four basic categories
Speaker 1: of tastes, sweet, salty, sour, and bitter. These categories are
Speaker 1: the building blocks of flavor and at the root of
Speaker 1: other tastes. Each primary taste triggers a particular taste receptor.
Speaker 1: The receptors can and do respond to multiple tastes. The
Speaker 1: four basic tastes went unchallenged for years. However, in the
Speaker 1: early nineteen hundreds, a Japanese chemist by the name of
Speaker 1: Kikune Keda set out to identify the compound in a
Speaker 1: common soup broth called kombu dashi that made it taste good.
Speaker 1: He was looking to find something that could be produced
Speaker 1: cheaply and easily that could add flavor to nutritious foods
Speaker 1: and thus entice people to eat better. He was also
Speaker 1: looking to make money, and wouldn't we all be lucky
Speaker 1: to make money doing something good for the world. In
Speaker 1: nineteen oh eight, he landed on the molecule glutamic acid
Speaker 1: as the key stuff in kambu or seek help that
Speaker 1: makes dashi so sippable. It's an amino acid, a building
Speaker 1: block of protein that we understand today occurs in lots
Speaker 1: of meats, cheeses, and vegetables, from steaks to parmesan to
Speaker 1: tomatoes and Kida. Further proposed that our detection of it
Speaker 1: is a fifth basic taste, a one that humans developed
Speaker 1: an affinity for because it occurs in these nutritious foods.
Speaker 1: In English would call this taste savory. But when Haita
Speaker 1: came up with a product that carries this taste, a
Speaker 1: salt format of glutamic acid called monosodium glutamate or MSG,
Speaker 1: he called the taste umami in his marketing materials, ubami
Speaker 1: being a colloquial term for tasty. Yes, the word umami
Speaker 1: is just an early nineteen hundred's marketing term. Kaida's research
Speaker 1: didn't really hit the Western world until the MSG company
Speaker 1: that he started began trying to expand outside of Asia
Speaker 1: in the nineteen eighties. By the way, MSG is fine
Speaker 1: for the vast majority of people to consume unless you're
Speaker 1: on a low salt diet. In general, if you feel
Speaker 1: a little weird after eating a dish that it's heavy in,
Speaker 1: you're probably just dehydrated that always drink water anyway. Researchers
Speaker 1: have since found the taste receptors responsible for sensing amino
Speaker 1: acids like glutamic acid, thus solidifying savory as a fifth taste.
Speaker 1: Now that the gate is open, however, other contend have
Speaker 1: entered the field. French researchers have identified a potential gustatory
Speaker 1: receptor for fat, so fatty might be a sixth taste.
Speaker 1: Other researchers have suggested that our basic tastes could further
Speaker 1: include metallic, watery and alkaline, the opposite of acidic. And
Speaker 1: just as scientists are re examining the basic tastes. They're
Speaker 1: also redefining the tongue map. The classic tongue map divided
Speaker 1: the tongue into regions of sensation bitter in the back,
Speaker 1: sour on the sides, salty on the front edge, and
Speaker 1: sweet at the tip. This concept also goes back to
Speaker 1: the early nineteen hundreds. A lot of work was being
Speaker 1: done in nutritional science at the time, but since then
Speaker 1: a research has determined that although the tongue does have
Speaker 1: varying degrees of sensitivity, some areas can perceive certain tastes
Speaker 1: better than others. There was no real truth to the
Speaker 1: strict tongue map. Furthermore, although taste receptors often react strongly
Speaker 1: to a single taste, most do respond to multiple taste stimulations.
Speaker 1: The primary tastes gave early humans clues about what food
Speaker 1: was good to eat and what was potentially harmful. Sweet
Speaker 1: foods had energy loaded carbohydrates. Salty foods had important vitamins
Speaker 1: and minerals. Savory foods had protein. Sour foods could be
Speaker 1: healthy like apples, or spoiled like rotten milk. Bitter things
Speaker 1: could be poisonous. And actually one bit of the tongue
Speaker 1: map was more accurate than the rest. The back of
Speaker 1: the tongue is particularly sensitive to better flavors. The raining
Speaker 1: hypothesis goes that this was useful and last ditch detection
Speaker 1: of toxic substances before we swallowed them. These days, the
Speaker 1: processed foods we eat are often painstakingly flavored by professional
Speaker 1: flavor chemists, so the tastes that we experience when we
Speaker 1: eat them are sometimes signifying nutritional value, but it isn't
Speaker 1: actually there, but we still crave and respond to our
Speaker 1: ancestral favorites. Of course, a person's taste is a lot
Speaker 1: more complicated than that. Physically, we perceive other flavors beyond
Speaker 1: the five ish primary tastes. Spicy foods can feel hot
Speaker 1: due to two different categories of compounds that both trigger
Speaker 1: the same nerve receptors in your mouth and knows that
Speaker 1: sense actual heat. They're chemically tricking your mouth into thinking
Speaker 1: that it's slightly on fire. Chili peppers and the capsaisin
Speaker 1: in them affect one type of nerve receptor. A plant
Speaker 1: in the mustard family, including masabi and other pungent things
Speaker 1: like cloves, garlic, cinnamon, and ginger, will activate a second
Speaker 1: type of heat receptor. This is also the receptor that
Speaker 1: registers the slight nasal burn of carbonation and sodas. Black
Speaker 1: pepper hits both of those Sesshuan peppercorn or any of
Speaker 1: the numbing hot dishes it's made with that activates both,
Speaker 1: plus yet another type of receptor, the same one that
Speaker 1: your body uses to sense what's basically tickles extremely light touches,
Speaker 1: like when a bug lands on you. It produces the
Speaker 1: same feeling as the pins and needles you get when
Speaker 1: a limb falls asleep, or when you hit your elbow
Speaker 1: just wrong, or feel a vibration, and so yes, tickle
Speaker 1: is a flavor. Evolutionarily, these plants probably developed these compounds
Speaker 1: to be unpleasant to mammals like us, and therefore to
Speaker 1: prevent us from eating that plant's fruit and thus crushing
Speaker 1: up its seeds before they have a chance to sprout
Speaker 1: and grow. But suckers, some of us humans decided that
Speaker 1: we enjoy those flavors or bitter tasting things like black
Speaker 1: coffee or artichokes. That's part of why, despite having figured
Speaker 1: out a lot about our taste buds and other flavor
Speaker 1: chema receptors, we still don't have a very good idea
Speaker 1: of how any given person's overall sense of taste works.
Speaker 1: Your brain doesn't just catalog the molecular makeup of a peanut,
Speaker 1: butter and jelly sandwich. It processes the smooth and soft
Speaker 1: and maybe crunchy textures and the cravable combination of salty,
Speaker 1: savory and sweet sensations, and maybe throws in a little
Speaker 1: nostalgia for a time that someone you love made a
Speaker 1: similar sandwich for you. The same sandwich eaten on two
Speaker 1: different days might even taste different, just based on your mood,
Speaker 1: like sometimes when you're upset, eating anything feels gross, and
Speaker 1: research has shown that hunger really can affect flavor. In
Speaker 1: a study from back in two thousand and four, groups
Speaker 1: of students who had not eaten in sixteen hours could
Speaker 1: perceive weaker sucrose and salt solutions than those who had
Speaker 1: eaten only an hour before. In order to perceive a taste,
Speaker 1: the students who had just eaten needed a sucros concentration
Speaker 1: fifty percent higher, and assault concentration doubled that of those
Speaker 1: who had not eaten. But apparently our poison detecting sense
Speaker 1: never rests. An empty stomach or full stomach had no
Speaker 1: effect on the perception of bitterness, speaking of it's time
Speaker 1: for me to go get a refill on my coffee,
Speaker 1: which I take with just a little bit of oatmelk.
Speaker 1: It's a matter of taste. Today's episode is based on
Speaker 1: the article how taste works on how stuffworks dot com,
Speaker 1: written by Sarah Dowdy. Brain Stuff is production of iHeartRadio
Speaker 1: in partnership with how stuffworks dot Com and is produced
Speaker 1: by Tyler Klain. Four more podcasts for my heart Radio,
Speaker 1: visit the iHeartRadio app, Apple Podcasts, or wherever you listen
Speaker 1: to your favorite shows.