Have you ever tried to be vegetarian but found it too difficult to stop eating meat? Your genes could be partly to blame, a new study suggests.
The research, published Wednesday in the journal PLOS ONE, identified a set of genes associated with people who adhered to a vegetarian diet for at least a year.
Nabeel Yaseen, the study’s lead author and a professor emeritus of pathology at Northwestern University, said the findings may indicate that sticking with vegetarianism isn’t solely a matter of willpower.
“The take-home message is that, based on your genetics, a vegetarian diet may or may not be appropriate for you,” Yaseen said. “You don’t need to blame yourself if this is something you can’t really stick with.”
The study compared the genetics of thousands of vegetarians and meat-eaters who shared their medical and lifestyle data with the U.K. Biobank, a biomedical research database containing information from about half a million participants in the U.K.
The study analyzed data from approximately 5,300 vegetarians and 329,000 meat-eaters, and identified three genes that are significantly linked to the choice of a vegetarian lifestyle. All three are located on a chromosome that has genes involved in brain function and lipid metabolism — the process in which fats are broken down for energy.
The results also pointed to 31 other genes associated with vegetarianism as well, though more weakly. Several of those genes play a role in lipid metabolism too.
“We are hypothesizing that maybe one’s ability to adhere to a vegetarian diet may have something to do with how they deal with fats in their body and how that affects brain function,” Yaseen said.
However, he added that the study simply highlights a genetic connection and does not assert that particular genes directly cause people to prefer a vegetarian diet.
For the research, Yaseen and his team focused on people they considered strict vegetarians — those who had not consumed animal flesh or meat products for at least a year. They determined who qualified based on two questionnaires that participants filled out for the U.K. Biobank. The first, administered four times between 2006 and 2019, asked participants to self-report whether they had eaten meat within the last year. The second, administered five times between 2009 and 2012, asked people to log everything they had eaten within the prior 24 hours.
The idea that our genes influence dietary preferences isn’t new or surprising. A study published last year also found links between people’s genes and the types of food they like, and aversions to certain foods have long been understood to have genetic ties.
For example, it’s fairly well-known that some people have a version of a gene that can lead them to dislike cilantro.
“The cilantro gene is actually an olfactory receptor in your nose that binds aroma compounds in cilantro,” said Joanne Cole, an assistant professor in the department of biomedical informatics at the University of Colorado School of Medicine who wasn’t involved in the new study. “Some people have a version of this gene that makes them smell and taste cilantro as soapy, and so they tend to not eat it as much.”
Yaseen said his findings, however, are novel in the way they establish a link between particular genes and vegetarianism.
A lot of past research, by contrast, has relied on comparisons of twins to investigate the role genetics play in dietary preferences.
Dr. Laura Wesseldijk, the lead author of one such twin study, said research she published in January found that genetics can “account for 70 to 80% of individual differences in abstinence from eating beef, pork, poultry, fish and shellfish.”
Wesseldijk, a behavioral geneticist at Amsterdam University Medical Centers who wasn’t involved in the new research, noted, however, that human traits are never determined by nature or nurture alone. Rather, “it’s all completely entangled,” she said.
When it comes to diet, Wesseldijk added, a person’s upbringing and surroundings — which in turn can be influenced by their religious and moral beliefs, health concerns or culture — play a large role.
“An environment can completely counteract something that is highly heritable, and the same goes with vegetarianism,” she said.
Yaseen, for his part, pointed out a couple key limitations of his study: For one, the research only included white caucasians. Other ethnicities were excluded, he said, to ensure that genes that may be associated with a particular race weren’t incorrectly linked with being vegetarian. So the research would need to be repeated in other groups to determine whether the findings apply more broadly.
Second, the study only examined a small fraction of the human genome, leaving open the possibility that additional genes may also be associated with being vegetarian.
Yaseen said he doesn’t have immediate plans for further research on the topic but could imagine a time in the future — after much more research has been completed — when it might be possible for experts to assess whether a vegetarian diet is a good fit for an individual based on their DNA.
“Hopefully, we’ll know more, and we’ll be able to maybe test people genetically and say, ‘OK, you know, this diet is good for you, or this diet is not good for you’ — like have more personalized dietary recommendations.”
Katie Mogg is an intern at NBC News.