Study links lingering sweet, bitter and umami loss after COVID to taste-bud defects

Scientists from the University of Colorado Anschutz, the University of Wisconsin and the Swedish University of Agricultural Sciences examined 28 people who continued to experience taste problems more than a year after COVID-19 infection. While most retained normal salty and sour perception, eight showed markedly reduced ability to detect sweet, bitter and umami flavors. Microscopic examination of taste-bud samples from 20 participants uncovered two abnormalities: a drop in messenger RNA that produces the PLCβ2 protein, which boosts taste-cell signaling for those flavors, and structural disorganization of the taste cells in several samples.

Because PLCβ2 is not involved in salty or sour detection, the selective loss aligns with the molecular defect. The research, published in Chemical Senses, offers the first concrete evidence linking long-COVID taste loss to specific cellular disruptions, though it remains unclear whether these changes can reverse or be treated.