It’s well understood that losing your sense of smell is a common symptom of Covid-19. Less well known is how much Covid-19 affects the ability to taste. A study published in JAMA Otolaryngology-Head & Neck Surgery (6 January 2022) has found it’s not as much as patients might think.
Much of what we experience as taste, or flavour, is actually what we smell. Gustation, or what we call “true taste” is identified by the sensory nerves in the tongue and mouth that allow us to detect sweet, savoury, bitter, salty and umami qualities in food. And there are two smell pathways in use whenever we eat; through the nose - orthonasal olfaction - and through the back of the mouth - retronasal olfaction. These different sensory pathways combine to give us the full flavour experience.
The research team in Italy wanted to understand whether Covid-19 directly affected true taste. They worked with 105 Covid-19 patients referred to an ENT clinic in Italy who still reported problems with taste and smell more than three months after infection. Putting them through a series of tests, the researchers were able to see what level of impairment was due to smell through the nose, smells received through the mouth, and what was due to true taste.
Only three out of 105 patients had no sense of true taste, but a normal sense of smell.
40% of patients were found to have lost true taste, as well as lost smell.
58% patients were found to have a normal functioning sense of true taste, but more than four out of five (83.6%) of those people had a severely reduced ability to smell.
The researchers identified that this initial study was small and limited, and several issues need to be addressed in further studies to be confident in the full picture. However they said the study, “uncovers overestimation of self-reported taste impairment and supports the use of validated psychophysical tests”
Unfortunately, the types of test used in this study are not easily accessible for everyone. Without knowing whether you have loss of smell, true taste, or both, it’s difficult to say how best to treat it. What we do know is that smell training has been demonstrated to support recovering the sense of smell. The high percentage of people in this study who reported “taste” loss but actually had smell loss suggests that smell training could give many people a good chance of recovering smell and taste.
The study is: Comprehensive Chemosensory Psychophysical Evaluation of Self-reported Gustatory Dysfunction in Patients With Long-term COVID-19. A Cross-sectional Study. Paolo Boscolo-Rizzo, MD; Thomas Hummel, MD; Claire Hopkins, MA(Oxon), DM; et al.
JAMA Otolaryngol Head Neck Surg. Published online January 6, 2022. doi:10.1001/jamaoto.2021.3993
Professor Hopkins and Professor Hummel are also members of AbScent's Advisory Board.
You can read the study in full here
Find out more about Smell Training here
January 17, 2022