Researchers have identified a specific genetic mutation that affects a person’s perception of the smell of decay. The study also found for the first time genetic mutations associated with the intensity of licorice and cinnamon odors. Our sense of smell is mainly controlled by olfactory receptors in the nasal cavity. Odor molecules bind to the recipient site and then send signals to the part of our brain responsible for processing odors. Of course, our responses to odors are complex and deeply intertwined with emotions and experiences, yet the sensitivity of olfactory receptors is also strongly influenced by genetics.
Perhaps the most famous genetically affected taste/smell is the infamous coriander. About 10 percent of people are thought to carry a genetic mutation that makes their olfactory receptors particularly susceptible to a molecule in coriander that produces a distinctive pungent soapy taste.
How olfactory genes affect human perception of certain odors is clearly understaffed. To illustrate these mysteries, a large team of Icelandic scientists recruited more than 9,000 subjects. Each participant subjectively reported reactions to six key odors: licorice, cinnamon, fish, lemon, mint, and bananas.
“We found sequence variations that affect how we perceive and describe the smell of fish, licorice and cinnamon,” explained Rosa Gisladottir of deCODE Genetics in Reykjavik, one of the study’s authors. “Because our sense of smell is so important to the perception of taste, these variations may affect whether we like foods that contain these smells.”
The most striking and novel genetic variant associated with odor sensitivity was found to be a molecule called thamamine (TMA). This particular compound is fundamentally responsible for the highly familiar smell of rotten fish.
The study found that a genetic mutation in the olfactory receptor gene called trace amine-related receptor 5 (TAAR5) can significantly reduce a person’s negative perception of TMA. In fact, the study even found that some subjects with the gene variant responded positively to the smell of TMA, describing it as similar to “caramel” or “rose.”
“The carriers of the variant found that the fish smell was less intense, less unpleasant, and less likely to name it accurately,” Gisladottir said. “There’s a lot of animal studies about TAAR5 about its role in the aversion to the hard connection of methamphetamine. Our findings extend the significance of this study to human odor perception and behavior. “
Unlike the discovery of the TMA gene variant, the other two findings in the study refer to mutations that are thought to increase olfactory perception. Two genetic variants were found, possibly related to increased odor intensity of licorice and cinnamon.
“We found a common variant in the olfactory receptor cluster, which is associated with increased sensitivity to trans musk, found in black licorice products, but also found in spices and plants such as octagonal fennel seeds, octagonal musk and musk,” Gisladottir added. “The carriers of the variant found that the licorice smelled stronger, more pleasant, and could be named more accurately. Interestingly, this variant is more common in East Asia than in Europe. “
Such studies are still early days, but they do note that there appears to be significant geographical diversity in these olfactory receptor gene variants. The researchers concluded that our sense of smell is still largely honed by the process of natural selection.
The new study was published in the journal Current Biology.