Taste plays a critical role in our continued existence. From helping us select safe choices to managing our metabolic processes, it’s on the front lines of food preferences and nutritional priorities. Taste also delivers more esoteric benefits including immediate gratification and mental recollection, making this sense a standout for both keeping us alive — and making life worth living.
But how exactly does it work? Let’s dive into the science of taste and discover why the tongue map we memorized in school doesn’t make the grade, how taste gets from buds to brains, why we’ve evolved to beat the bitter and what new links researchers now see between the senses.
It’s a familiar flavor profile: Our tongue is designed to taste sweet in the front and bitter in the back, while sour and salty get the sides. As noted by the NCBI, however, this popular paradigm “is based on an incorrect reading of an illustration of the tongue.” Any part of our in-mouth muscle has the capacity to detect any taste — though it’s true that the back-bitter connection outpaces the others as a way to prevent humankind from ingesting poisonous or spoiled substances.
Recent work has also uncovered a “new” flavor: umami. This Japanese word translates as “pleasant savory taste” and is often associated with the tastes of broth, meat, mushrooms, cheeses or gravies. There’s also research to suggest the existence of specialty receptors for detecting “fatty” taste — for example, a specific receptor has been identified which responds to linoleic acid, commonly found in natural fats and oils.
It’s worth noting that hot and spicy don’t pass the taste test. Unlike the other five (or six) flavors, hot and spicy are pain responses to temperature and touch. In the same way some people can stand the heat outside and others prefer a shady spot, some love a dose of mouth pain on their plate while others bank on bland.
Getting Technically Tasty
So how does taste get from your buds to your brain? As noted by the International Food Information Council (IFIC) Foundation, it all starts with papillae — tiny bumps that house your taste buds. Those near the back of your mouth are extremely sensitive to bitter tastes and can cause a gag or spit reaction to reduce the risk of eating something dangerous. But that’s just the start — there are three specific types in different areas on your tongue:
- Fungiform papillae — Located near the tip of your tongue, there are approximately 400 of these papillae, and they contain between three and five taste buds each.
- Foliate papillae — Found on the sides of your tongue, these 20 (or so) papillae look like folds and contain hundreds of taste buds each.
- Circumvallate papillae — Look for them on the back of your tongue forming a “V” shape — these circumvallate papillae are big enough to see. There are approximately 12 in your mouth, each with thousands of buds that are bitter-sensitive.
Once your taste buds capture food particles, they analyze the flavor and activate the facial, glossopharyngeal and vagus nerves which send signals to the base of your brain. From there, they split up — some signals head to the ventral forebrain to trigger emotions and memories, while others detour to the dorsal region and may cause you to crave specific flavors.
While taste is foundational to human function, it’s not a static sense. As noted by a recent study from Human Molecular Genetics, there’s evidence to suggest that as human toxin-avoidance strategies evolved thanks to the use of fire and readily available food information, our involuntary reaction to bitter stimuli has reduced. As a result, we’re able to better tolerate bitter flavors — such as coffee or alcohol — that would have caused historic humans to reflexively reject.
This taste transition can also be seen in micro-scale across human maturation; while children are predisposed to prefer high-calorie, sugar-dense foods, adults often find them overwhelming — but have greater tolerance for bitter beverages or food that falls outside typical taste categories.
The See Food Solution
Research has already explored the taste-smell connection — if your olfactory orifices are at a nasal nadir, your food simply won’t taste as great. This taste/smell teamwork also explains why the scent of fresh-baked goods can prompt a salivary response; our taste buds know what’s coming, and they want it now.
But this isn’t the full taste tale. As noted by Science Daily, work from a UC Santa Barbara team found that opsin protein — which binds to retinal and creates the critical rhodopsin required for vision — also plays a role in functional food selection. Research with fruit flies found that when given the choice between sugar and sugar spiked with aristolochic acid, the flies avoided the acid-option even when concentrations were incredibly low. The reason? Aristolochic acid easily bonded with opsins in the same site used by retinal to amplify the “signal” of the acid, in much the same way resulting rhodopsin amplifies dim light to improve vision.
While there’s no confirmation that humans leverage the exact same opsin protein option, it’s a safe bet that the proteins we depend on for sight also impact what we taste.
Taste the Rainbow
The science of taste isn’t simple. Old diagrams don’t do it justice, and the complex interaction of taste receptors can produce both immediate cravings and emotional responses. What’s more, taste research is in transition. There’s data to suggest that we’re becoming less bitter with age, and new discoveries demonstrate that critical sight compounds play a key role in targeting taste response.