Published May 03, 2012
Do you pass when it comes to pork? If you do, the reason you don’t like the taste of bacon or ham may lie in your genes.
According to a new study from Duke University Medical Center in Durham, N.C., researchers have discovered that about 70 percent of people have two functional copies of a gene called OR7D4. The gene is linked to an odor receptor that detects a compound called androstenone – a chemical in male mammals, most commonly in pork.
People who have only one or no functional copies of OR7D4 don’t mind the scent of pork; those with two copies, however, turned their nose up at the smell.
“Even though we found this gene, we didn’t expect to see such strong food preference,” said Hiroaki Matsunami, a Duke associate professor of molecular genetics and microbiology and one of the lead researchers for the study. “With any food – if it’s meat or bread or fruit – you find hundreds of volatile chemicals, and this gene only interacts with one of these hundreds of chemicals.”
“But we found this nice, surprisingly clear answer to this, showing this OR7D4 would explain or predict how you like the meat.”
For the study, researchers added different amounts of androstenone to existing pork meat samples, then asked 23 participants rate the meat based on the smell and whether or not they liked the taste.
After each rating, DNA samples were collected from the participants to determine the genotype of their OR7D4 gene. Every single person sensitive to the androstenone had the RT/RT genotype – or two copies of the RT gene.
According to Matsunami said this gene could be responsible for certain people’s aversion to other kinds of meat as well.
“The male pork meat contains relatively high levels of androstenone, but you can also find it in other types of meat,” said Matsunami. “In fact, androstenone is also found in human sweat, so it’s not a pig specific chemical.”
Androstenone is a well known pheromone created during the mating process in pigs, giving much more significance to Matsunami’s findings. Currently both Europe and the U.S. only sell pork from females or castrated males, meaning the meat contains very low levels of androstenone. In non-castrated pigs, the androstenone levels are over 30 times as much
Since Europe is currently considering banning castration of its swine, countries in that region run the risk of losing more consumers of pork because some people won’t enjoy the taste anymore.
As for why the OR7D4 gene illicits this reaction, Matsunami isn’t exactly sure, but he has a few ideas. He said in order to clarify his theories, he is eager to continue research on the gene to learn more about its role.
“Why do we need this particular gene? That’s a more difficult question to answer,” Matsunami said. “There’s speculation that this chemical might have an additional role, that it may also influence the physiology of the people who are smelling it. The reason people think that is because in the pig, it facilitates courtship behavior, so it’s an important chemical for their survival. Maybe the same chemical is having the same subtle effect on the human population.”
Matsunami also hopes to expand the team’s studies into other areas of the world.
“We’re very interested in knowing this genotype distribution in various populations,” Matsunami said. “People in certain areas don’t eat pork at all. Maybe these people have more special kinds of genes. Or maybe if you go to indigenous populations of people in Alaska who only eat these very special meats, maybe they’re very different with their receptor genes.”
While Matsunami will continue to work extensively to understand the OR7D4 gene’s origin, he will only be able to understand its effects on others, because he himself is impervious to androstenone’s sway.
“Personally I cannot smell this chemical,” Matsunami joked. “But when I talk about it in the classroom, I will bring in this chemical. It’s interesting because some students are very sensitive to it and are really disgusted by it.”