PHILADELPHIA — A new study from a team of researchers at the Perelman School of Medicine at the University of Pennsylvania, the Monell Chemical Senses Center, and the Philadelphia VA Medical Center, reveals that a person’s ability to taste certain bitter flavors is directly related to their ability to fight off upper respiratory tract infections, specifically chronic sinus infections.  The new research is published in the latest edition of the Journal of Clinical Investigation.

Most humans experience five types of tastes: sweet, salty, sour, bitter, and savory.  The sense of taste is mediated by taste receptor cells which are bundled in our taste buds. “Sour” and “bitter” taste sensations alert the body to harmful foods that have spoiled or are toxic. But based on genetics, up to 25 percent of the population cannot detect certain bitter flavors (non-tasters), 25 percent can detect exceedingly small quantities (super-tasters), and the rest of us fall somewhere between these two extremes.

So what exactly does drinking a cup of bitter coffee have to do with chronic sinus infections, which account for approximately 18-22 million physician visits in the U.S. each year?  Recent investigations have shown that these taste receptors (T2Rs) are also found in both upper and lower human respiratory tissue, likely signaling a connection between activation of bitter tastes and the need to launch an immune response in these areas when they are exposed to potentially harmful bacteria and viruses.

“With this information in mind, we wanted to better understand the exact role that bitter taste receptors play in the upper airway, especially between these super and non-tasters,” says Noam Cohen, MD, PhD, assistant professor of Otorhinolaryngology: Head and Neck Surgery, staff physician at the Philadelphia VAMC, and senior author of the new study.

Cohen and his colleagues formulated the following hypotheses around the connection: (1) bitter taste receptors are functional in the nose (upper respiratory tract), and each receptor detects a specific type of bacteria; (2) upon activation by a specific bacterial product, the bitter taste receptor initiates a local defensive response to combat the attacking bacteria; and (3) genetic variability of the bitter taste receptors alters the vigorousness of the response, thus leaving certain individuals with very strong defenses and others with weak defenses against a specific bacteria.

To test these hypotheses, the team grew cell cultures from sinus and nasal tissue samples collected during sinus surgical procedures.  These cultures develop cilia, produce mucus, and reflect many of the defensive workings found inside the nose and sinuses. 

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