Of all the tastes (sweet, sour, umami, bitter, salty), bitter is kind of an outlier. There’s only one kind of taste receptor for sweetness and one for umami, as Danielle Reed, the associate director of the Monell Chemical Senses Center, once explained to PBS, but we have 25 different types for bitterness.
One reason for the difference may be because bitterness, an evolutionary mechanism to keep us from ingesting anything dangerous, can be a life-or-death sensation. “But some things that are bitter are not necessarily bad for us in all circumstances,” Reed said, adding that bitter compounds can help us heal. “So one hypothesis is that we need to be really able to sense low concentrations of bitterness because when we’re sick, we want to be able to sample all the different plants and find things that help us get better, but we don’t want to eat too much of them.”
In a new video for Eater, Reed explained one way that scientists are building on that hypothesis: They’re investigating whether the bitter sense can be manipulated to help doctors personalize medication to each patient.
“You go to the doctor and you have some symptoms, and the doctor wants to prescribe a medicine for you,” she said. “Imagine you do a simple taste test and the medicine tastes bitter to you. Maybe that predicts you’re not going to respond to it as well. Maybe you’ll go on to a different medicine.” This would help gauge the effectiveness of your treatment before you start it, rather than adopting a wait-and-see approach.
There’s already some evidence for this approach: Last year, Reed co-authored a study that found a link between taste receptors and healing time after surgery — specifically, people who had a gene that made them more sensitive to certain bitter tastes were in better shape six months after sinus surgery, reporting less pain and an easier time sleeping than people who didn’t have the same gene. (In a past study, the researchers had established that the specific bitter receptor in question — which can be found in the nose as well as the mouth — has an immune purpose as well as a sensory one, helping the body fight off bacteria.)
“Your receptors are on your tongue and they’re responding to whatever you throw in your mouth, but it turns out those receptors may have been repurposed to do that … and their original purpose was in other parts of the body,” she told Eater. We already know that taste buds don’t just live on the tongue; there are also taste receptors in your nose, at the back of your throat, and in your esophagus, and little kids also have them inside their cheeks. And in the future, if the research bears out, it’s possible that the sense of taste will prove itself useful throughout the body in ways we don’t yet understand.