Bitter is Better for Bronchial Tubes

By Amy Cowen on November 10, 2010 1:12 PM

Do you wrinkle up your nose at the taste of something bitter? That's partly what your taste buds do—help warn your body against something that is bitter and could be poisonous.

While your tongue may or may not like the bitter taste of foods like radishes and dandelion greens, your lungs might react differently! A team of researchers from the University of Maryland and Johns Hopkins recently discovered that the lungs have "taste receptors" (like the ones on your tongue). That was a surprise, but the bigger surprise was that rather than contracting and withdrawing from bitter substances, the lungs appear to respond positively to bitter substances—the airways expand and open up, which makes it easier to breathe.

An Accidental and Surprising Discovery

Scientific discovery doesn't always go as planned. In fact, discovery often involves following the trail of experimental results even if they lead away from the initial experiments—or fail to support initial hypotheses.

Researchers were studying the human lung muscle receptors responsible for regulating how our airways contract and relax when they realized that taste may not be all in the mouth. When the team of researchers realized they had stumbled upon a strange scenario—taste buds in the lungs—they could have thought their data was wrong. They could have just shrugged and continued with their initial course of research. After all, taste buds were not what they were looking for! They could have just assumed the presence of taste receptors was an odd and unimportant artifact of human evolution....but instead, they investigated.

A Wrong Hypothesis

The team continued experimenting and testing, hoping to determine how taste receptors in the lungs "work." Further experiments confirmed that the taste receptors are receptors for bitter substances, just like the receptors found on the human tongue.

It is thought that bitter taste receptors on the tongue evolved as part of the body's self-defense system against harmful or poisonous substances, many of which have a bitter taste. If you taste something bitter, you are more likely to spit it out and, as a byproduct, save yourself from being poisoned.

Initial guesses were that the taste receptors in the lungs would respond to "bitter" in the same way the tongue does... with a shiver and a shake! Speculation was that the presence of these "bitter" receptors in the lungs was again related to self-defense. Researchers guessed that when confronted by a bitter substance, the receptors would react and cause the airways to constrict, thus letting in less potentially contaminated air.

But they were wrong.

The taste receptors behaved exactly the opposite of what researchers expected. The presence of the reactors does, indeed, seem related to the body's self-defense mechanisms. But instead, of constricting the airways, bitter substances caused the lung muscles to relax the airways, increasing the air flow.

Understanding "why" the taste receptors work differently in the lungs compared to on the tongue required formulating a new hypothesis, their original one regarding the behavior of the taste receptors already disproven. The researchers now believe that the bitter taste receptors are present in the lungs because they can help detect bacteria that cause lung infections like pneumonia.

Bacteria often secrete compounds that are "bitter." If the taste receptors in the lungs sense these bitter compounds, they may give orders to help open up the airways, helping the patient breathe more easily—and potentially helping the patient survive the infection. This is the direction their research is taking as they track down how "taste" in the lungs really works.

A Result that May Help Millions Breath Better

Will eating extra bitter foods help you fight off an illness? Probably not. But this research may help open up new possibilities in the development of better and more effective asthma medications.

The team's findings were certainly unexpected, but now that the bitter taste receptors have been identified and their behavior tracked, drug companies can use these findings to develop asthma drugs that will target these receptors, thus allowing asthma patients to breath more easily during an asthma attack.

Student Research

Students interested in exploring questions related to taste receptors or breathing can tackle projects like the ones listed below from the Science Buddies Project Ideas directory.

Projects related to taste receptors: