A new study provides the first direct biological evidence explaining why some people continue to experience taste loss long after recovering from COVID-19.
Researchers have uncovered specific biological changes in taste buds that could help explain why a small number of people continue to struggle with taste loss long after a COVID-19 infection.
The study, published in Chemical Senses, is the first to directly connect patients’ lingering taste complaints with measurable abnormalities inside the cells responsible for detecting flavor.
What causes long-term taste loss after COVID-19?
To explore the cause of long-term taste disturbances, scientists from the University of Colorado Anschutz and two universities in Sweden examined 28 non-hospitalized individuals who reported altered taste more than one year after having COVID-19.
Key findings:
8 of 28 patients showed clearly abnormal taste test scores
11 patients reported specific loss of sweet, bitter, and umami taste
Salty and sour tastes were largely preserved
To better understand the biological basis of these symptoms, the researchers collected taste bud biopsies from 20 of the participants.
Molecular defect identified in taste receptor cells
The research team, organized by Göran Hellekant, PhD, of the University of Wisconsin and the Swedish University of Agricultural Sciences, found that certain taste receptor cells contained lower levels of messenger RNA (mRNA). This mRNA is needed to produce a protein known as PLCβ2, which plays a central role in transmitting taste signals for sweet, bitter, and umami flavors.
“PLCβ2 acts like a molecular amplifier inside taste cells,” said Thomas Finger, PhD, professor of cell and developmental biology at the University of Colorado Anschutz and corresponding author of the study. “It strengthens the signal before it’s transmitted to the brain. When levels are reduced, the taste signal weakens.”
Cells that detect salty and sour tastes rely on different signaling mechanisms and do not depend on PLCβ2. This difference may help explain why those particular tastes were largely unaffected in the participants.
