A rose in a garden on a summer afternoon. An apple pie slowly baking in the oven on a chilly fall day. Humans have the ability to smell and taste a vast array of scents and flavors. But it is clear that different people experience different levels of sensitivity to odors. Who is to say, exactly, how that apple pie smells to someone else?
Now, two studies by Richard Newcomb and colleagues at The New Zealand Institute for Plant and Food Research in Auckland, published in the journal Current Biology on August 1, 2013, suggest that genetic variation may play a role in an individual’s sensitivity to specific odors, as well as the perception of those odors through smell and taste.
Newcomb and colleagues selected ten odors found in fruit and dairy products and then tested subjects to see how sensitive they were to each. Using a genome-wide microarray, the researchers identified genetic associations for four of the scents. These variations were independent of one another, meaning that sensitivity to one odor wasn't related to sensitivity to any other odor.
"Four out of ten odors showing a strong genetic association is a really high ratio," says Jeremy McRae, a co-author on both papers. "If you extrapolate a little and think of the hundreds or thousands of odors you find in foods, there might be a similarly large genetic determinant for many of those different odors." This implies that each individual could have a completely unique sensitivity profile to odors, making their experience of eating a particular food different from anyone else’s. As a result, we may each inhabit our own special "flavor world".
To find out if these sensitivities alter the experience of eating a certain food, the team conducted a second study. Here, they took the odor with the strongest genetic association and conducted sensory tests, having subjects drink solutions and eat foods that were flavored with the odor. The data showed that those people with a genotype making them more sensitive to the odor described foods spiked with it as "fragrant" and "floral", while those who were less sensitive described the foods differently. But differences in sensitivity did not mean than an individual was more or less likely to say they liked or disliked the odor. That, the researchers found, was more dependent on its concentration and context.
McRae says the next step is to look at odors within the foods where they are usually found, in order to see how different genotypes respond to an odor in its usual setting. And Plant and Food Research, his employer, has some ideas for how to begin to apply this information in the marketplace. "We've thought about screening our breeders for these genotypes to see if they happen to be sensitive or insensitive to these odors.” Growers would like to make sure that the fruit they're breeding reflects what people enjoy eating, and in the long term, they might even try to tailor fruits to appeal to people with different genotypes.
1. McRae, J.F., et al. 2013. Identification of Regions Associated with Variation in Sensitivity to Food- Related Odors in the Human Genome. Curr Biol. doi: 10.1016/j.cub.2013.07.031. [Epub ahead of print]
2. Jaeger S.R., et al. 2013. A Mendelian Trait for Olfactory Sensitivity Affects Odor Experience and Food Selection. Curr Biol. doi: 10.1016/j.cub.2013.07.030. [Epub ahead of print]