A new study suggests that vegetarian diet's genes may exist, and they can determine which people can stick to a strict meat-free diet.
About 5% of American adults consider themselves vegetarians, according to 2018 data. The diet is more prevalent among younger adults: 8% of those aged 18 to 34 and 7% of people 35 to 54 say they adhere to a vegetarian diet, compared to only 2% of adults 55 and older.
Researchers from Northwestern Medicine compared the U.K. Biobank genetic data from 5,324 strict vegetarians who don't consume fish, poultry,red meat, or seafood to 329,455 omnivore controls. All study participants were white Caucasians.
The researchers identified three genes significantly associated with vegetarianism and another 31 genes with potential association. Several of these genes, including two of the top three (NPC1 and RMC1), are involved in lipid (fat) metabolism and/or brain function.
Nabeel Yaseen, professor emeritus of pathology at Northwestern University Feinberg School of Medicine and corresponding study author, says that plant products differ from meat in complex lipids, especially sphingolipids, that play critical roles in nervous system development and function.
"My speculation is there may be lipid component(s) present in meat that some people need. And maybe people whose genetics favor vegetarianism are able to synthesize these components endogenously. However, at this time, this is mere speculation, and much more work needs to be done to understand the physiology of vegetarianism"Dr. Nabeel Yaseen
One of the identified genes, VRK2, is also linked to anorexia. Strict long-term vegetarianism is about twice as frequent in females than in males. Eating disorders are also more common in females, and some studies suggest a link between a vegetarian diet and eating disorders. Therefore, the researchers hope that a better understanding of what makes people vegetarians may also help to uncover mechanisms underlying eating disorders, especially anorexia.
The study findings should be generalized with caution because the U.K. Biobank participants tend to be healthier and of better socioeconomic status than the general population. They are also older and more likely to be female.
What prevents us from choosing the vegetarian diet?
Vegetarians remain a small minority in the U.S., and the true number of those strictly following the diet is likely much lower, as 48% to 64% of self-identified vegetarians report consuming fish, poultry, or red meat.
According to Yaseen, this suggests that environmental or biological constraints override the desire to adhere to a vegetarian diet.
Moreover, food and drink preference is partly driven by how an individual's body metabolizes it. For instance, many don't like coffee or alcohol the first time they try it, but they develop a taste over time because of how these drinks make them feel.
"I think with meat, there's something similar. Perhaps you have a certain component — I'm speculating a lipid component — that makes you need it and crave it," Yaseen adds.
Benefits of plant-based diets
The benefits of a vegetarian diet are well established. Vegetarians are less likely to develop several health conditions, including ischemic heart disease, cancer, and type 2 diabetes. They also have lower body mass indexes (BMI) compared to those who eat meat.
A recent study published in the European Heart Journal indicates that plant-based diets, such as vegan and vegetarian, cut low-density lipoprotein (LDL) cholesterol, sometimes called bad cholesterol, by 10%. Moreover, it reduces apolipoprotein B, the main protein in LDL cholesterol, by 14%, reducing the risk of cardiovascular disease.
Plant-based diets are suitable not only for humans but also for the planet's health. According to a study that appeared in Nature Food, vegans have just 30% of the dietary environmental impact of high-meat eaters. The researchers looked at factors such as greenhouse gas emissions, land use, water use, water pollution, and biodiversity loss.
As vegetarians are at a higher risk of a deficiency of some nutrients, such as vitamin B12 and iron, and inadequate protein intake, it is essential to find nutritious alternatives.
Legumes, soya beans, nuts, eggs, and dairy are excellent sources of protein, whereas high levels of iron are found in green leafy vegetables, potatoes (especially their skins), hemp seeds, and dark chocolate.
The authors say that future studies will provide a better understanding of the physiologic differences between vegetarians and meat-eaters. This could enable the production of better meat substitutes.