Can our taste buds give us clues for new medical treatments?

by Jessica De Loma Olson

[dropcap]O[/dropcap]f our five common senses, we might think taste is at the bottom of our list when considering their relative importance. If we had to lose a sense, almost no one would think twice about discarding our sense of taste. However, the relevance of taste for survival is well known despite being often underestimated.

When humans were hunter-gatherers, it is likely our taste receptors were critical to our survival. Unpleasant tastes are often associated with poisonous substances or non-edible goods that should be avoided. This is the case for bitter substances, usually characteristic of alkaloids derived from plants that are poisonous, and sour ones, normally related to rotten food.

But our sense of taste does not only serve to warn us about potential dangers – it is also related to pleasure. The refreshing taste of freshly-picked vegetables or the juiciness of a piece of meat can get any of us to salivate. And this is no coincidence. Both our senses of taste and smell initiate the process of digestion, which means that, as you start eating, the stomach automatically becomes active even before the food gets to it, preparing itself for digestion.

Another interesting fact is our propensity towards sweets. If you have a sweet tooth, you do not have to feel guilty anymore – genetics are behind this. Different alleles of the gene Tas1r3, which codes for one of the subunits of the sweet receptor, have been associated with differences in perception and tolerance for sweet tastes. This could explain why sweets are a soft spot of many people, whilst others simply cannot stand them.

If you have a sweet tooth, you do not have to feel guilty anymore…

Another aspect to this is our perception of bitter taste and resulting facial expressions. Remember that feeling of eating broccoli? You would probably stick your tongue out, wrinkle your nose, and retract your upper lip. Now, think about what face you would put on if you were “grossed-out” by the look of rotten food. Feel familiar? The connection between visceral disgust (induced by looking at rotten food) and bitter taste has been widely studied. Both produce the same contraction of facial muscles and have been linked to the same neurological area, the anterior insular cortex. Even though there seems to be an obvious connection, the biological relevance of this remains unknown.

Many questions have yet to be solved, but our interest in understanding this sense is growing. During the process of uncovering answers, there have also been attempts to alter and trick it. Miraculin is a glycoprotein naturally found in Synsepalum dulcificum, otherwise known as the miracle berry. This molecule binds to sweet receptors on the tongue and when exposed to sour substances, changes its conformation and activates the wrong sweet receptors. In this situation, sour is interpreted as sweet, opening the doors to a universe of confusion for our taste buds.

Sometimes, tricking our sense of taste can involve much more than altering our tasting perceptions. The presence of bitter receptors (TAS2R) has been documented in smooth muscle cells in the airways. Studies have shown how bitter substances can activate these receptors to induce the relaxation of bronchial muscles. Such discoveries could bring new therapeutic options to treat asthma, showing us that there is more to learn about our senses than we know.

This leaves us with a final question: are we capable of manipulating our sense of taste to suit our own purposes? Getting children to eat their vegetables or even treating diseases such as asthma are only some of the possibilities the future may hold. As long as our insatiable appetite for scientific discovery does not subside, we inch ever closer to the taste of victory.