Lingering COVID taste loss is tied to molecular defects in taste buds that weaken sweet and savory signals

Among 28 people who still had taste problems more than a year after catching COVID-19, researchers found reduced activity in the gene for PLCβ2, a protein that amplifies sweet, bitter and savory signals inside taste cells. Thomas Finger of the University of Colorado Anschutz is the corresponding author of the study, and Göran Hellekant, of the University of Wisconsin and the Swedish University of Agricultural Sciences, organized the research. ScienceDaily carried the university’s summary on Oct. 19, 2026.

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None of the 28 volunteers had been hospitalized for COVID-19, which makes the group a picture of the ordinary long-term taste complaint rather than of severe disease. The findings are an association between symptoms and tissue measurements, and the team does not claim that the virus has been proven to cause each change it found.

PLCβ2, the amplifier for sweet, bitter and savory

The molecular clue sits in a protein that most readers have never heard of. Finger described it plainly: “PLCβ2 acts like a molecular amplifier inside taste cells.” Sweet, bitter and umami, the savory taste, depend on that amplification before their signals travel on toward the brain, while salty and sour detection does not appear to rely on it. That split matches what many participants reported, since salt and sour tastes were largely unaffected while difficulty clustered around sweet, bitter and savory flavors.

The research was published in Chemical Senses in a paper called “Taste dysfunction in long COVID”, with Hanna Morad, Tytti Vanhala and Marta Kisiel among the nine named authors. The journal’s article lookup resolves to the same record, which lists online publication on May 18, 2026, so the October coverage is a later write-up of a paper that was already out.

Testing covered all five basic tastes: sweet, sour, bitter, salty and umami. Because the picture was selective, with the amplifier-dependent tastes hit hardest, the authors read the pattern as pointing at a specific piece of signaling machinery and not at a general numbing of the tongue, though a single small study cannot rule out other contributors.

Twenty biopsies and what the tissue showed

Every one of the 28 participants reported a taste disturbance, but standard testing sorted them unevenly. According to the Swedish University of Agricultural Sciences record of the paper, only three scored below the 10th percentile for their age and sex, yet 11 had a complete loss of at least one taste quality, and the losses involving sweet, umami and bitter were more common. Those losses tracked with lower messenger RNA for PLCβ2 and for the sweet and umami receptor subunit Tas1R3 in the taste buds.

The team took small tissue samples from the tongue’s taste papillae in 20 of the volunteers and examined structure, nerve supply and gene expression. The pictures were mixed. Finger said some subjects had normal-looking taste buds while others showed structural disorganization, and the authors report that a few isolated PLCβ2-positive cells looked abnormal even where the overall architecture held up.

That mixed result is why the findings are best read as molecular defects in taste buds rather than wholesale destruction of them. The abstract states that taste bud structure and nerve supply were largely preserved, and its authors conclude that long-lasting taste dysfunction after COVID-19 is uncommon and does not reflect widespread damage to the periphery of the taste system.

A small sample, and a smell problem that can pass for taste loss

The study is small, and the summaries do not say how the participants with abnormal test scores overlap with those who lost a particular flavor. Nor do they say whether the changes can reverse, or whether a treatment aimed at the taste-signaling pathway would help anyone. The university’s summary describes the work as the first direct biological evidence tying persistent taste problems to measurable changes in taste cells, a claim that comes from the authors’ side rather than from an independent review.

Context from the National Institute on Deafness and Other Communication Disorders is useful here. Its page on taste disorders names the five basic tastes as sweet, sour, bitter, salty and umami, and says true taste loss is rare, because most people who think they have a taste disorder actually have a problem with smell. It also says taste often returns when the underlying cause, such as an infection, resolves.

For the 28 people studied, the problem had lasted well past that point, more than 12 months, which is what made them useful to the researchers. What the work adds is a measurable biological signature to compare against in larger and more varied groups, and a specific protein to watch. Whether that protein turns out to be a useful target for treatment is a question the researchers leave open, and no therapy is proposed in the summaries of the work. For now the practical message is limited: anyone with a persistent change in taste can ask an ear, nose and throat specialist, who diagnoses taste disorders through exams and taste tests, to separate a true taste problem from a smell problem.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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