Sensitivity to bitter flavors linked to immune system protein, Monell scientists find

If broccoli loses its appeal when you’re sick, blame your immune system. According to new work from the Monell Chemical Senses Center in Philadelphia, an immune protein, TNF, helps determine how bitter taste is perceived.

 TNF is critical in fighting off infections, and white blood cells will churn it out once they detect invading microbes.

“We found this protein is also in the taste buds,” said senior author and molecular biologist Hong Wang, “and plays a role in regulating bitter taste.” The results were published this month in the journal Brain, Behavior, and Immunity.

In one key experiment, Wang’s team spiked water with different concentrations of quinine, which gives tonic water its bitter flavor, and offered it along with regular water to mice. Normal mice avoided the bitter water even at very small doses. But mice incapable of producing TNF lapped up the liquid — up to a point.

“When the TNF is not there, then these types of mice will wait until a much higher concentration to start to avoid bitter tastes,” said Wang.

It’s not clear why TNF has an effect on bitter taste receptors, but Wang said one possibility is to protect people when they’re already in a more vulnerable state.

“Bitter taste is a warning signal,” she said. “Bitter taste is related to toxins or other compounds that may be trouble to us.”

Of course, the heightened sensitivity also makes it harder to take certain medications and keep weight on, especially for those suffering from chronic conditions.

Wang said she hopes her experiments raise awareness about what happens to taste buds during illness — and that caregivers will think more about what kind of foods or medications are tolerable for patients with extra sensitive palates.