Taste Buds Show Molecular Damage a Year After COVID-19

What is wrong inside the taste cells?

The research group, organized by Göran Hellekant, PhD, of the University of Wisconsin and the Swedish University of Agricultural Sciences, identified reduced amounts of messenger RNA (mRNA, the molecule that carries instructions for building proteins) needed to produce a protein called PLCβ2.

That protein plays an essential role in how taste receptor cells communicate with the brain: it amplifies the signals generated when the tongue detects sweet, bitter and umami flavors. Without sufficient levels, those signals may become too weak to register normally.

"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."

The finding may also explain the selectivity of the deficit. Cells that detect salty and sour tastes rely on different signaling mechanisms that do not depend on PLCβ2, which could allow those sensations to survive even when the other taste channels falter.

Were the taste buds themselves changed?

Yes. The damage was not confined to molecular signaling. Under the microscope, the researchers found that some participants had alterations in the physical arrangement of their taste cells.

"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."

Together, the two findings suggest that lingering taste problems after COVID-19 may involve multiple biological disruptions at once — affecting both how taste cells are organized and how effectively they transmit information to the brain.

Why can the loss last more than a year?

The question sharpens when set against the tongue's normal pace of repair. Taste bud cells renew themselves roughly every two to four weeks, yet the researchers found signs that the molecular processes required for normal taste signaling remain disturbed far beyond that window in some people.

Most individuals who experience taste changes during COVID-19 regain normal taste within weeks or months. A small group does not. "Our findings offer measurable evidence of long-term taste disruption in some post-COVID patients long after the virus has been cleared," the authors write.

What remains uncertain?

The study is small — 28 participants, 20 of whom provided tissue samples — and the findings are preliminary. The researchers could not yet determine whether the molecular abnormalities eventually return to normal on their own, or whether treatments designed to restore healthy taste signaling could speed recovery.

For now, the work gives patients and clinicians something concrete: a biological signature, not merely a reported symptom. The next step is to learn whether that signature can be reversed.