Feb. 7, 2014

By Medical Discovery News

Have you ever wondered if we all sense the world in the same way? Evidence suggests that the sense of smell is highly individualized, based on genetic differences. This could revolutionize scents and food flavors into custom-designed creations for individuals.

Humans have specialized neuronal cells within the lining the nasal cavities, part of what’s called the olfactory epithelium. The surface of these cells, like much of the nasal cavity, is covered with mucus. Odor molecules dissolve into this layer and are detected when they bind to receptors on the neurons. This sets off a string of biochemical events that produces a signal, which travels along the olfactory nerve to the olfactory bulb of the brain. Then that signal is transferred to different regions of the brain’s cerebrum. Here odors can be distinguished and characterized. These signals are stored in long-term memory, which is linked to emotional memory. That’s why particular smells can evoke memories. This process is quite complex due to the highly evolved sense of smell in humans.

The genes that are involved in olfactory or smell sensations are not well understood. People do perceive odors differently, but researchers have only identified genes for certain odors. For example, human perception of cilantro has been linked to the olfactory receptor OR6A2 and grassy odors have been linked to receptor OR2J3.

New Zealand scientist Dr. Richard Newcomb tested the ability of almost 200 people to smell 10 different chemicals associated with the key odors of things like apples and blue cheese. Then these individuals’ genomes were completely sequenced, and genetic variances that could account for these olfactory differences were determined. For four of the chemicals tested, clusters of genes were identified as being able to detect these odors. Interestingly, these genes were located on different chromosomes. Newcomb’s work almost doubled the number of genes known to be connected with the sense of smell. For beta-ionone, a chemical associated with the smell of violets, a single gene was shown to allow people to sense that fragrant flower’s scent. Overall, the result of this study was that people are capable of experiencing chemical smells in different ways.

This opens the door for scientists to define an individual’s olfactory profile. If it’s understood how an individual perceives smells, a chef could personalize food just for their senses. Imagine walking into a restaurant and handing your server a card with your olfactory profile based on your genes. And violá! A dinner prepared with the seasonings and flavors you find most pleasing. With continued research, our sense of smell may be able to experience this scenario and more. 

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