Why is fish smell unpleasant for some people?
Researchers have found that some people carry a mutation in a particular gene that makes fish odour less intense. An olfactory receptor gene called trace amine-associated receptor 5 (TAAR5) was pinpointed as the reason for this smell variation.
The study conducted in Iceland involved examining the olfactory genes in humans. A sniff test was conducted for over 9,000 people. Participants were asked to smell odours from pen-like devices. After sniffing each pen, the researchers asked what the smell was, the intensity, and the pleasantness of that smell. They sniffed key ingredients found in licorice, cinnamon, fish etc. The TAAR5 variant affects perception of fish odour containing trimethylamine, a compound found in rotten and fermented fish. In the smell tests, those participants who have the gene variant were more likely to not smell anything when presented with the fish odour or could only smell it with less intensity and often named the odour incorrectly.
The results were published in Current Biology. A note from Cell Press adds that while humans have fewer olfactory genes compared to other species, some of the genetic variations that people do carry makes them more sensitive to particular smells such as licorice or cinnamon, not less. The researchers say they will continue to collect data on odour perception and have also planned to investigate the smell deficits in COVID-19 patients