Researchers studying people who could not taste food more than a year after COVID-19 found measurable abnormalities inside their taste buds. In a study published in Chemical Senses, scientists from the University of Colorado Anschutz and two Swedish universities examined 28 non-hospitalized participants with long-lasting taste disturbances. Eight had clearly abnormal taste scores, and eleven reported particular trouble with sweet, bitter, and umami flavors, while salty and sour detection remained largely intact.
Tissue samples from 20 participants revealed lower levels of messenger RNA for PLCβ2, a protein that amplifies taste signals before they are sent to the brain. The study authors describe PLCβ2 as a molecular amplifier inside taste cells, and when its levels are reduced, the signal for certain flavors weakens. Microscope examination also found structural disorganization in some taste buds, suggesting that both molecular and architectural problems may contribute to persistent symptoms.
The findings help explain why taste loss can last so long even though taste cells normally renew every few weeks. However, the study leaves important questions open, including whether these molecular abnormalities can eventually correct themselves and whether treatments aimed at restoring taste signaling could help patients recover.