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Experts say fresh vegetables are a key component of a healthy diet. Maria Manco/Stocksy
  • Vegetarianism has been practiced worldwide for thousands of years for cultural, moral, and health reasons.
  • Researchers now say some people may be more genetically predisposed to choose to follow a vegetarian dietary pattern.
  • Experts point out that genetics are often only one factor out of many in determining health outcomes.

Some people may find it difficult to maintain a strictly vegetarian diet.

According to new research, your genes may help explain why.

A study published October 4 in the scientific journal PLOS One notes that vegetarians make up less than 5% of the population in the United States. Of that 5%, about half to two-thirds of self-identified vegetarians consume fish, poultry, or red meat at least occasionally.

The researchers suggest that genetic factors may help explain why some people adhere to a strictly vegetarian diet while others do not.

How did the researchers test their theory, what did they find, and what do experts have to say about it?

Participants in this study were selected from the UK Biobank, a database that includes about 500,000 people.

Samples — including blood — were collected from each participant, allowing the researches to identify single-nucleotide polymorphisms (SNPs, pronounced snips).

SNPs are a common type of genetic variation. Everyone has many SNPs and they help to determine a variety of biological characteristics — from eye color to disease susceptibility — in a complex interplay with each other.

Some SNPs affect metabolism and brain function and could make it more or less difficult for your body to function properly while on a vegetarian diet.

Participants in the study also completed at least one of two dietary questionnaires. One was a general dietary questionnaire and the second asked participants to recall their diet from the previous 24 hours.

After screening, the study retained 5,324 vegetarians and 329,455 control subjects.

The SNPs of each group were analyzed and compared to each other to determine whether certain SNPs were associated with a vegetarian diet.

In the end, 11 specific genes were identified by researchers as potential contributors to vegetarianism.

Does this mean that your diet is predetermined by your genes? Not quite, experts say.

“This study does not, in fact, show any causational role of these potentially vegetarian SNPs,” said Megan Wroe, a wellness manager and registered dietitian at the Wellness Center of Providence St. Jude Medical Center in California who was not involved in the study.

“Even if these SNPs were found in a genetic assessment, it does not mean, based on this data, that they should in fact follow a vegetarian diet or that anything negative would happen if they didn’t. Just like anything else, you can have a genetic predisposition but never see that outcome. You can show you have genetic risk factors for cancer and never get cancer. There are too many other factors at play, such as movement, stress, and environmental toxins.”

— Megan Wroe, registered dietitian

There are other reasons to be cautious with the study’s results, experts advised.

“The study was well done overall, but any time you use food journals and recalls as the main identifying factor of how a person eats you run into unreliable data,” said Wroe.

“The findings from this study are not generalizable since the people who participated in the study tended to be female, older, healthier, and of high socioeconomic status,” said Dr. Amanda Velazquez, the director of Obesity Medicine at the Center for Weight Management and Metabolic Health at Cedars Sinai Medical Center in Los Angeles, who was not involved in the study.

“We have to be cautious to apply these findings to the entire population until more research is done to study more diverse populations,” Dr. Velazquez told MNT.

While many people choose vegetarianism for cultural, moral, religious, or environmental reasons, the diet plan also can affect your health.

“This study defines vegetarian as not eating any animal flesh or product at all, which is actually vegan,” Wroe said.

“I typically do not recommend a strict vegan diet for most people. Vegetarian, pescatarian, or omnivorous with small portions of sustainably raised meat are the most health-promoting diets for majority of people.”

Jordan Hill, the lead registered dietitian with Top Nutrition Coaching, told MNT that “some of the potential health benefits from following a vegetarian diet include:

  • reduced risk for chronic diseases
  • weight management
  • improved digestion

“With an emphasis on plant foods, fruits, and vegetables, those that follow a vegetarian diet may intake more fiber, micronutrients, and antioxidants than their counterparts,” said Hill, who was not involved in the study.

“It’s important to note that a vegetarian diet can still include unhealthy processed foods, which may not support the previously mentioned health benefits,” Hill added.

Hill cautioned that you also should be aware of insufficiencies associated with a vegetarian diet. Possible nutrient deficiencies that may occur with a vegetarian diet include:

  • low vitamin B12
  • low iron
  • low calcium
  • low omega-3 fatty acids
  • inadequate protein intake

Some people may decide that a strictly vegetarian diet isn’t for them, but that doesn’t mean they will be in poor health.

“It’s important for individuals to make dietary choices that align with their personal preferences and cultural factors, in addition to their overall health goals. There’s no right or wrong way to eat and finding what’s best for the individual is encouraged,” said Hill.

If you choose to include meat in your diet, Hill recommends choosing healthier options. Examples of lean meat include

  • chicken
  • turkey
  • fish

When it comes to red meat, the World Cancer Research Fund International recommends limiting red meat consumption to three 4- to 6-ounce servings per week, Hill noted

“We should aim to minimize factory-farmed meat as much as possible, but I am a big advocate of including grass-fed or pasture-raised meats on a regular basis for the quality nutrients they provide that cannot be obtained from plants,” Wroe added.

Eating meat or not eating meat doesn’t necessarily have to be a strict choice.

“Focus less on whether you need to follow vegan or vegetarian or flexitarian diet — and simply start cooking and using less highly processed packaged products. Most of us would be so much healthier if we simply ate homemade food more often,” Wroe said.

Experts recommend gradually transitioning if you’re considering switching to a meatless diet.

“Start including vegetarian protein sources such as beans, lentils, nuts, and seeds. Try substituting one of these for an animal protein daily. Often times in diet culture, we have viewed it as ‘all or nothing’ and forget that even small steps can make a difference.”

— Dr. Amanda Velazquez, obesity and weight management expert