Who doesn't love the scent of a juicy slab of bacon? People with two functional copies of a gene linked to the OR7D4 odor receptor, that's who.

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People go meat-free for a variety of reasons, ranging from environmental causes to health concerns. Another reason might be a genetically determined tendency to dislike the smell of meat, according to a recent study.

Researchers from Duke University Medical Center and colleagues in Norway found that about 70% of people have two functional copies of a gene linked to an odor receptor called OR7D4, which detects androstenone, a compound similar to testosterone that is found in male mammals, commonly in pork.

People with one or no functional copies of the gene can tolerate the scent of androstenone much better than people with two copies can. Reactions to androstenone vary broadly from person to person, the study found, with some comparing it to urine or sweat, while others saying it smelled sweet like vanilla. Some people have no reaction to it at all, and others who are highly sensitive think it’s repulsive.

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Lead study author Dr. Hiroaki Matsunami, an associate professor of molecular genetics and microbiology at Duke, had identified the gene for the OR7D4 odor receptor in his previous research. Then, scientists in Norway contacted him to take a closer look at how certain genotypes might influence people’s perception of the smell of pork.

The Norwegians’ interest in the study was piqued because the European Union was considering a ban on castration of male pigs due to animal welfare concerns. Castration drastically reduces the amount of androstenone in pork, so the researchers were concerned about whether consumers would still find meat palatable if the ban were approved.

The researchers looked at a total of 23 participants. Thirteen were consumers and 10 were professional sensory assessors — people with sensitive noses who can successfully differentiate certain smells. Both groups smelled and tasted pork with varying levels of androstenone and were asked whether or not they liked it. Based on their reactions, the subjects were divided into sensitive and insensitive groups.

The study showed that all of the androstenone-sensitive participants had two functional copies of the OR7D4 gene, while those who were better able to tolerate the smell of pork had only one or no copies. “The data raise the possibility that more consumers will dislike male meat as a result of a castration ban,” the authors wrote in the study.

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“It was surprising how this one gene could have such a clear influence on the preference of the food,” says Matsunami. “Taste is a complex mixture of taste, smell, texture and temperature. They combine to create a taste image in the brain. The olfactory component that plays the greatest role in whether you like the pork or not is determined by this gene.”

Matsunami says the findings are likely the first of many that will be discovered in the future. Perhaps studies can reveal how odor receptor genes function in populations such as vegetarians or those in the Middle East or near the Arctic, who do not eat pork or other similar meats. Further research could also be useful to product developers, who would probably like to know which receptors correspond to which flavors.

“We do not know all of the genetic components involved in preference, but we may find this in other kinds of food — even vegetables and fruit — and we can address the question, What is the genetic influence behind food preference?” says Matsunami.

The study was published online in the journal PLoS ONE.

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