AsianScientist (Aug. 6, 2013) – There are some smells we all find revolting. But for a handful of odors, different people display differing sensitivities and perceptions of the smells. A pair of studies appearing in the journal Current Biology now identifies the genetic basis behind such differences.
The researchers, led by Prof. Richard Newcomb of The New Zealand Institute for Plant and Food Research, tested nearly 200 people for their sensitivity for ten chemical compounds commonly found in foods. They then searched through the subjects’ genomes for areas of the DNA that differed between people who could smell a given compound and those who could not.
Four of the ten odors had genetic associations, suggesting that differences in the genetic make-up determine a person’s ability to smell these compounds. The smells of these four odorants are familiar to those who can smell them (though their names may not be): malt (isobutyraldehyde), apple (β-damascenone), blue cheese (2-heptanone), and β-ionone, which smells floral to some people and is particularly abundant in violets.
“We were surprised how many odors had genes associated with them. If this extends to other odors, then we might expect everyone to have their own unique set of smells that they are sensitive to. These smells are found in foods and drinks that people encounter every day, such as tomatoes and apples. This might mean that when people sit down to eat a meal, they each experience it in their own personalized way,” says Dr. Jeremy McRae, the lead author of one of the studies.
When the scientists compared the differences in sensitivities between human populations in different parts of the world, they found no sign of regional differentiation. In addition, the ability to smell one of the compounds does not predict the ability to smell another.
So, which are the genes that determine our ability to perceive certain odors?
Dr. McRae and colleagues found that the genetic variants associated all lie in or near genes that encode odorant or olfactory receptors. The odorant receptor molecules sit on the surface of sensory nerve cells in our nose. When they bind a chemical compound drifting through the air, the nerve cell sends an impulse to the brain, leading ultimately to the perception of a smell.
In the case of β-ionone, the smell associated with violets, the researchers managed to pinpoint the exact mutation in the odorant receptor gene OR5A1 that underlies the sensitivity to smell the compound and to perceive it as a floral note. This indicated that people who are less good at smelling β-ionone also describe the smell differently, as sour or pungent, and are less likely to find it pleasant.
“Knowing the compounds that people can sense in foods, as well as other products, will have an influence on the development of future products. Companies may wish to design foods that better target people based on their sensitivity, essentially developing foods and other products personalized for their taste and smell,” says Prof. Newcomb.
The articles can be found at:
Jaeger SR et al. (2013) A Mendelian Trait for Olfactory Sensitivity Affects Odor Experience and Food Selection.
McRae JF et al. (2013) Identification of Regions Associated with Variation in Sensitivity to Food-Related Odors in the Human Genome.
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Source: Cell Press. Photo: Muffet/Flickr/CC.
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