If you don鈥檛 find the smell of fish particularly off-putting, you may have an olfactory gene mutation that makes these odours seem less strong and disagreeable.
K谩ri Stef谩nsson at Icelandic genomics firm deCODE Genetics and his colleagues have identified a gene, TAAR5, that affects how people perceive odours containing trimethylamine, a compound found in rotten and fermented fish.
To study how genetics affects our sense of smell, the researchers asked 9122 Icelandic adults to smell six odours that were presented in pen-like devices. The odours had ingredients found in fish, liquorice, cinnamon, lemon, peppermint and banana.
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After sniffing each odour, the team asked the participants to name the smell and also rate its intensity and pleasantness on a 7-point scale.
The participants also had their genomes sequenced, and the researchers correlated the odour responses with the sequences of olfactory genes. They found three genes of interest, variations of which corresponded to differing smell perceptions. In a separate sample of 2204 people, the team confirmed that two of these genes were linked to increased smell sensitivity and one, TAAR5, was linked to fishy smells specifically.
In smell tests, people with a particular variant of TAAR5 were more likely to smell nothing when given the fishy odour, or to describe it with neutral or positive descriptors unrelated to seafood, such as 鈥渃aramel鈥� or 鈥渞ose鈥�.
The variant affects 2.2 per cent of聽Icelanders, compared with 0.8 per cent of southern Europeans and 0.2 per cent of Africans.
鈥淚t seems to be some sort of local selection. In Iceland we have been living on fish mostly for thousands of years,鈥� says Stefansson.
鈥淭AAR5 is a very conserved gene, so it鈥檚 very similar across species, probably because it has been important to protect us against harmful microorganisms,鈥� says Rosa Gisladottir, also at deCODE. Trimethylamine is also present in bad breath, faeces and blood.
The researchers found other gene variants, which were correlated with a more intense perception of liquorice and cinnamon smells.
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