Some people become vegetarians for their health; others do so for ethical or religious reasons. Now a new study shows that people may avoid certain kinds of meat because they're genetically predisposed to find its odor offensive.
Pork that comes from uncastrated male pigs is sometimes marred by an odor commonly referred to as boar taint. One of the two pheromones responsible for boar taint is androstenone, a steroid molecule related to testosterone and produced in the testicles.
Not all people can detect androstenone, but for those who can, the scent can resemble onions, urine, or feces - enough to put one off bacon for quite a while.
Boar taint might not seem like much of a problem in the US or Canada, since most of the meat sold in these countries comes from female or castrated male pigs. But the EU may soon be getting a big whiff of it, thanks to calls to ban pig castration over animal welfare concerns.
So Norwegian scientists and Duke University researchers teamed up to examine how a gene called OR7D4, which encodes a receptor for androstenone, could influence a person's taste for pork from intact male pigs. They reported their results on Wednesday in the journal PLoS ONE.
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The study examined the reactions of 23 people - 13 ordinary consumers and 10 professionals trained in sensory profiling - to samples of cooked meat with different levels of androstenone. The researchers had added androstenone to some samples, but none contained levels beyond those normally found in the wild.
When they examined blood samples from the subjects, the researchers found that people with two copies of OR7D4 gene tended to rate meat with more androstenone as less favorable, while people with one or no copies of the gene could tolerate it.
Duke University molecular geneticist and senior author Hiroaki Matsunami was quick to add that OR7D4 copy number is not the sole determining factor in whether or not a person can tolerate a muskier pork chop.
Of course there are many more genes and factors involved in the food tasting experience, he says.
Furthermore, one of the subjects with two copies of the gene initially couldn't detect androstenone, but later gained the ability after being exposed to the compound for about six weeks, according to Matsunami.
Though the study is fairly small, Matsunami and his co-authors say their finding raises a lot of interesting questions for future research.
A person with the right genes could be a much more effective meat inspector than someone who can't smell boar taint, the authors suggested.
It would also be interesting to examine odor receptor genes in different kinds of populations - such as those from Middle Eastern countries with cultural taboos against pork, or in avowed vegetarians, Matsunami speculated.
A genetically-gifted ability to detect boar taint may also affect a person's taste for other meat.
You can still find androstenone in a variety of animal species, even though the amount is lower compared to pork meat, Matsunami says.
Louis Perusse of Quebec's Laval University, a researcher unaffiliated with the PLoS ONE paper, pointed out that OR7D4 is just one of hundreds of genes involved in odor sensing.
Perusse and his colleagues have taken a larger view of the link between odor sensing genes and eating. They examined the relationship between different versions of OR7D4 and other olfactory receptor genes and eating behavior traits in a study of 890 subjects published in February in the journal Physiology & Behavior.
One of the results that they found is that people with a certain variant of the OR7D4 gene tended to report that they were less susceptible to hunger pangs. The variant was also associated with reduced fat levels.
Perusse says the PLoS ONE study is a small piece of the puzzle, but it's a good way to establish a link between odor perception and food choices.