Why food still tastes different for some COVID-19 survivors

Some people who recovered from COVID-19 continue to experience changes in their sense of taste more than a year after infection, with new research suggesting that the virus may cause lasting alterations in taste cells.

A study published in Chemical Senses examined 28 people with persistent taste disturbances following COVID-19. None had been hospitalised during their illness. Taste tests showed that eight participants had clearly abnormal results, while 11 reported difficulty detecting particular flavours, especially sweet, bitter and savoury tastes. Their ability to recognise salty and sour flavours remained largely unaffected.

Tissue samples taken from the taste buds of 20 participants revealed reduced levels of a protein known as PLCβ2, which helps taste cells detect sweet, bitter and savoury flavours and transmit signals to the brain.

Researchers suggested that reduced levels of the protein could weaken these signals, making certain flavours harder to recognise. The findings raise questions about why taste disturbances persist despite the normal renewal of taste cells, which typically occurs every two to four weeks.

Although most people recover their sense of taste within weeks or months after COVID-19, the study provides evidence that changes in taste cells may persist in some survivors long after the infection has cleared.

Similar symptoms were documented among COVID-19 patients in Nigeria during the pandemic. A study involving 46 COVID-19-positive adults at isolation centres in Abuja and Ibadan found that eight participants, representing 17.4 per cent, experienced loss of taste during infection, while 14, or 30.4 per cent, reported loss of smell.

Published in the Annals of Ibadan Postgraduate Medicine in 2021, the study documented the effects of the infection on Nigerian patients but did not establish how many continued to experience the symptoms after recovery.

A virologist, Prof. Oyewale Tomori, attributed differences in recovery among survivors to individual health conditions, the extent of damage caused by the infection and the body’s ability to repair itself.

He said that while some people recovered completely, others continued to experience complications, adding that similar variations occurred with other diseases. Tomori warned that prolonged loss of taste and smell could affect more than people’s enjoyment of food, as persistent loss of appetite could compromise nutritional status.

He also highlighted safety concerns associated with loss of smell, noting that affected individuals might be unable to detect gas leaks or poisonous substances in their surroundings.

On whether the symptoms could become permanent, he said their duration remained uncertain, although some affected survivors could still recover.

“We don’t know how long. We can only say that so far, since people have had it in 2020, 2021, and they’re still having it, therefore, that can last for that period,” he said.

He advised people experiencing persistent loss of smell to seek medical attention from ear, nose and throat specialists, who could assess their condition and recommend available treatment options.

Further evidence of lingering symptoms emerged from a study involving 274 COVID-19 survivors who attended an outpatient clinic in Lagos State. Published in BMC Infectious Diseases in March 2021, the study found that 112 participants, representing 40.9 per cent, reported persistent symptoms after discharge.

Seven participants, or 2.6 per cent, experienced altered taste, while 24, representing 8.8 per cent, reported loss of appetite. Another 17 participants, or 6.2 per cent, experienced weight loss.

Although the Nigerian studies documented taste disturbances among patients and survivors, they did not establish how many continued to experience the problem for a year or longer.

The latest findings do not explain every case of prolonged taste disturbance, and further research is needed to establish whether the changes in taste cells can be reversed and what treatments could restore normal taste perception.

For Nigerians who experienced changes in taste during the pandemic, the findings highlight the possibility of longer-term effects of COVID-19. More local research is needed to determine the number of survivors still affected years after recovering from the infection.