The Mystery of Losing Your Taste From Long COVID May Finally Have an Answer

A common symptom that many experienced during a COVID-19 infection was a loss of taste. While most affected individuals regained their sense of taste within a few weeks, some experienced a persistent loss over several months. If a COVID-19-related taste dysfunction lasts longer than three months, it is a recognized symptom of Long COVID.

Now, researchers from Sweden and the U.S. have uncovered molecular and structural changes in some taste buds of patients with taste abnormalities after a COVID-19 infection, offering the first plausible explanation for why a small group of people lost their taste for an unusually long time.

The study, published in Chemical Senses, is a crucial step toward understanding the molecular causes behind COVID-19-related taste dysfunction, paving the way for developing treatments to mitigate patients’ taste loss.

Read More: Turns Out Some Smells May Be Processed in the Same Brain Area as Taste

COVID-19 and Long-Lasting Taste Loss

The researchers invited 28 individuals who reported prolonged taste dysfunction at least one year after a COVID-19 infection. To understand the extent of their taste deficit, they underwent the Waterless Empirical Taste Test (WETT), which, among other things, measures the ability to detect each of the five main taste qualities (sweet, salty, sour, bitter, and umami) on an eight-point scale using more than 50 strips.

The research team identified eight individuals with definite abnormal test scores, as well as eleven participants who specifically mentioned losing only sweet, bitter, and umami taste. Interestingly, salty and sour tastes were mostly unaffected.

Hoping to find a cause, the scientists took a closer look at taste bud biopsies obtained from 20 individuals. Since the COVID-19 virus is known to infect cells of the oral cavity by docking at a specific cell receptor, the research team believes direct virus-caused damage to taste bud cells is likely, amplified by subsequent inflammation, dysregulation of the immune system, and changes to saliva composition that often follow a COVID-19 infection.

Changes in Taste Buds May Weaken Flavor Signals

Analyzing the taste bud biopsies proved quite insightful. Some samples showed unusually low levels of the genetic material that produces an important protein involved in detecting sweet, bitter, and umami flavors, called PLCβ2, which is not found in salty and sour taste cells.

“PLCβ2 acts like a molecular amplifier inside taste cells,” said study co-author Thomas Finger, professor of cell and developmental biology at the University of Colorado Anschutz, in a press release. “It strengthens the signal before it’s transmitted to the brain. When levels are reduced, the taste signal weakens.”

Besides pinpointing this specific molecular change, many samples showed disorganized taste buds or unusual, isolated PLCβ2 cells, which have not been seen in normal subjects before.

“Some subjects had normal-looking taste buds, while others showed structural disorganization,” Finger said. “This suggests that both molecular and architectural changes may contribute to persistent taste dysfunction.”

Opening Doors for Better Diagnostics and Treatment

Under normal circumstances, taste bud cells are replaced roughly every other week, compensating for any damage that might occur in the meantime (like accidentally biting your tongue and destroying some taste cells). Even for people with COVID-19-related taste loss, the sensation normally returns after a few weeks.

Now, researchers may have found an explanation for why some patients experience longer-lasting taste loss by observing distinct disruptions in cellular signaling processes in a small group of affected individuals. They also state that this prolonged taste dysfunction occurs rarely and, luckily, does not appear to be based on large-scale defects of the entire taste apparatus.

The team also pointed out the relevance of studying the causes of taste loss, as sensory loss can impact nutritional intake and reduce emotional well-being, with individuals consistently reporting a negative effect on their quality of life. Studies like this open the door to better diagnostics and future treatments to bring back life to every bite.

This article is not offering medical advice and should be used for informational purposes only.

Read More: Why Do Viruses Like COVID-19 and the Flu Mutate Rapidly and What Does it Mean for Vaccines?

Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article: