Long after the acute fever and fatigue of COVID-19 have passed, some people find that the pleasure of a meal has quietly thinned, and a small new study offers a first physical clue as to why. Researchers who examined taste-bud samples from twenty people whose taste had stayed dulled for more than a year found less of a protein that strengthens the signals of sweet, bitter and savory flavors. The finding, published in Chemical Senses, is a careful opening rather than a conclusion: the group was small, had no comparison line, and the wider evidence still points most strongly toward smell. It is
Taste Bud Biopsies in Long COVID Patients Point to Reduced Signal Protein Behind Muted Flavors
Some people with COVID-19 have lived with dulled taste for more than a year, reducing enjoyment of food for years after infection.
A molecular amplifier inside taste cells may have gone quiet
Mark
Why does a protein in a biopsy matter to someone who just can't taste their food?
Mimi
Because it's a measurable change in taste cells. For people told it's all in their heads, that's a different footing.
Luke
Careful, though. It's a measurable change in 20 biopsied people, and the summaries describe no comparison group. We don't know how unusual those PLCβ2 levels are.
Mark
And why would one protein dull three tastes?
Mimi
Sweet, bitter and umami cells all use PLCβ2 in their signaling chain. Salty and sour use other pathways, and those tastes were largely spared.
Luke
That's the proposed mechanism, a possible explanation. The study shows reduced messenger RNA, not that this reduction causes the loss.
Mark
Taste cells renew every two to four weeks. Why doesn't taste just come back?
Mimi
The researchers saw signs the disruption can outlast many renewals, which hints that new cells may develop differently. But that wasn't tested.
Luke
Right, that's a question, not a result. And a 2024 JAMA Network Open study tied lasting flavor complaints mostly to smell damage. The two may be different patient groups, but nobody has shown that yet.
Mark
So what should someone with lasting taste loss do?
Mimi
See a primary care doctor or an ENT who can test taste and smell separately. There's no treatment from this finding.
O Pulso
- A year after infection, some people still cannot taste sweetness, bitterness or savory depth as they once did, and their meals have grown flat.
- Biopsies from twenty affected people point to lower levels of PLCβ2, a signal-amplifying protein inside taste cells.
- Salty and sour tastes mostly held up, complicating a neat explanation and hinting at more than one kind of damage.
- The study has no comparison group and only twenty biopsies, so researchers cannot yet say how unusual these levels truly are.
- Larger studies with control groups are needed before any therapy can be tested, and no approved treatment exists today.
- For now the finding lands as a promising lead, not a settled answer, and patients are urged to seek testing from a doctor or ENT specialist.
Long after the acute fever and fatigue of COVID-19 have passed, some people find that the pleasure of a meal has quietly thinned, and a small new study offers a first physical clue as to why. Researchers who examined taste-bud samples from twenty people whose taste had stayed dulled for more than a year found less of a protein that strengthens the signals of sweet, bitter and savory flavors. The finding, published in Chemical Senses, is a careful opening rather than a conclusion: the group was small, had no comparison line, and the wider evidence still points most strongly toward smell. It is a reminder that the senses are tangled together, and that understanding a lingering loss may take patience before it leads anywhere useful.
Researchers took tiny samples of taste buds from twenty people whose sense of taste had stayed impaired for more than a year after COVID-19. In those samples they found reduced activity of a protein that boosts the signals for sweet, bitter and savory flavors. The work appeared in Chemical Senses and was led by researchers at the University of Colorado Anschutz together with Swedish universities, with twenty-eight people taking part in total.
The picture was uneven. Eight participants had clearly abnormal taste scores, and many struggled to detect sweet, bitter and umami, while salty and sour were largely spared. The protein at the center of the study, PLCβ2, appears to act as a molecular amplifier in the cells that sense those three flavors, which may explain why they dimmed together. Tissue also varied, with some participants showing normal-looking taste buds and others showing structural disorganization.
The puzzle is that taste cells renew every few weeks, so the disruption persisting for years suggests something deeper, possibly affecting how new cells develop. The limits are real, though. There was no comparison group, and a 2024 national study tied lasting flavor loss mostly to smell, which matters because much of what we call taste is really smell. Those who are struggling are advised to seek testing from a doctor or ear, nose and throat specialist, and to be wary of unproven cures. Larger studies must now confirm whether low PLCβ2 is truly part of the story.
Researchers took tiny samples of taste buds from 20 people whose sense of taste had stayed impaired for more than a year after COVID-19, and found something specific: reduced activity of a protein that amplifies sweet, bitter and savory signals inside taste cells.
The work appeared March 2 in the journal Chemical Senses and drew fresh attention this month after ScienceDaily featured it. It was led by researchers at the University of Colorado Anschutz, working with two Swedish universities, and organized by Göran Hellekant of the University of Wisconsin and the Swedish University of Agricultural Sciences. Twenty-eight people took part. None had been hospitalized for COVID-19, and all reported taste problems lasting longer than a year.
The testing showed an uneven picture. Eight of the 28 had clearly abnormal scores on taste tests, and 11 had trouble detecting particular tastes, mainly sweet, bitter and umami, the savory quality found in broth and aged cheese. Salty and sour were largely spared.
The biopsies offered a possible reason. The samples showed reduced messenger RNA for PLCβ2, a protein that boosts the signal in cells that detect sweet, bitter and umami. Thomas Finger, corresponding author and a professor of cell and developmental biology at CU Anschutz, described it, according to the university, as acting like a molecular amplifier inside taste cells. Because all three of those taste types depend on PLCβ2, a shortfall in one protein could dull them together. Salty and sour cells use different signaling pathways that don't rely on it, which may explain why those tastes held up. The tissue itself varied: Finger said some participants had normal-looking taste buds while others showed structural disorganization, suggesting both molecular and structural changes may be involved.
The finding raises a puzzle. Taste bud cells normally turn over every two to four weeks, so damage to individual cells would usually be repaired quickly. The researchers found evidence that the signaling disruption can persist well beyond many rounds of renewal in some people. That leaves open a possibility the study did not test: that whatever changed may affect how new taste cells develop, not just the cells present during infection. The team said more work is needed to learn whether the dysfunction can fully reverse and whether therapies could restore normal signaling, according to the Swedish University of Agricultural Sciences.
The limits are plain. Only 28 people were tested and 20 biopsied, and published summaries do not describe a comparison group without long COVID, so it is hard to know how unusual the PLCβ2 levels are. The results may apply only to a subgroup. Other research points elsewhere: a 2024 national study in JAMA Network Open found taste problems had largely cleared a year after infection while smell problems lingered, and suggested long-term taste complaints may reflect damage to smell-sensing tissue. Much of what people call flavor comes from smell. In that study, smell problems affected 30.3% of people with prior COVID-19 versus 21% of those without a known infection. The two findings may describe different patients. The new authors call theirs the first direct biological evidence of taste cell changes, and others will need to confirm it.
The scale of the broader problem is large. A 2022 BMJ analysis led by Singapore General Hospital estimated about 4.4% of COVID-19 patients may develop long-lasting taste problems, roughly 12 million people worldwide at the time, though 79% had recovered taste within 30 days.
For those still living with dulled food, the practical advice is to see a primary care doctor or an ear, nose and throat specialist, who can test taste and smell separately and rule out causes such as medications, dental problems or nerve conditions. Notes on which tastes seem weaker, and whether smell has changed, help that visit. No approved treatment follows from this finding, so supplements marketed as taste cures deserve caution. Sudden weakness, facial drooping or trouble swallowing alongside taste loss calls for prompt care.
What comes next is larger studies with comparison groups and tests of whether taste signaling can be restored. For now, low PLCβ2 is a possible, not proven, explanation.
Citações Notáveis
PLCβ2 acts like a molecular amplifier inside taste cells.— Thomas Finger, CU Anschutz professor and corresponding author
Some subjects had normal-looking taste buds, while others showed structural disorganization.— Thomas Finger
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