Can Genetics Truly Predict Vegetarianism?

The term “vegetarian” has expanded to encompass a spectrum of dietary choices, embracing everyone from committed vegans and flexible flexitarians to conscious reducetarians, seafood-loving pescatarians, and mindful practitioners of the macrobiotic diet.

However, despite the growing discourse on the benefits of reducing meat consumption, the number of individuals adopting vegetarianism has declined over the years. ¹ Notably, meat consumption per person has been on a steady rise over the last several decades. ²

All of this begs the question: is Vegetarianism coded in our genes? Let’s examine the studies to find out.

UK Biobank Study: Examining Vegetarianism and Genetics

In a comprehensive analysis conducted as part of a Genome-Wide Association Study (GWAS), Dr. Nabeel Yaseen and his team examined the genetic profiles of over 5,324 individuals who identified as strict vegetarians and 329,455 meat-eaters, all aged above 40. These participants willingly provided their extensive medical and lifestyle data to the UK Biobank. 

The UK Biobank is a large-scale biomedical database and research initiative in the United Kingdom, established to collect and store a wide range of health and genetic information from over 500,000 participants, making it one of the most extensive resources of its kind.

To identify strict vegetarians, the researchers used two detailed questionnaires administered between 2006 and 2019. The first questionnaire, repeated four times, required participants to self-report their meat consumption within the past year. The second, conducted five times between 2009 and 2012, asked individuals to meticulously document their dietary intake over the previous 24 hours.

Identification of Genetic Variants Associated with Vegetarianism

When comparing vegetarians to meat eaters, the genetic analysis unveiled a SNP, rs72884519, situated on chromosome 18 near the TMEM241 gene, which exhibited a strong association with vegetarianism.

(A SNP, which stands for Single Nucleotide Polymorphism, is a common type of genetic variation that occurs in a person’s DNA sequence. It involves the replacement of a single DNA building block (nucleotide) with another nucleotide at a specific position in the genome).

Those carrying the T-allele of this SNP were 12% more likely to embrace a vegetarian lifestyle than individuals lacking this allele. 

Furthermore, 202 genetic variants were detected with weak evidence of a potential association with vegetarianism. 

Specific Genes Implicated in Vegetarianism

Through an in-depth analysis of genetic variant data at the individual gene level, the study revealed robust evidence implicating three specific genes:

• RIOK3,
• RMC1,
• and NPC1

Notably, the NPC1 gene displayed the highest number of functionally relevant SNPs (rs1788799, rs1624695 and rs1623003). These SNPs have the potential to impact the activity and expression of the NPC1 (Niemann-Pick disease, type C1) protein, potentially leading to variations in individuals’ dietary preferences. 

An additional 31 genes were found to have limited evidence of being associated with vegetarianism, indicating that these genes might potentially contribute to the development of vegetarian dietary preferences.

Lipid Metabolism, and Brain Function in Relation to Vegetarianism

Lipids are diverse organic molecules, including fats, oils, and phospholipids, that serve essential roles in energy storage, cellular structure, and various biological processes within living organisms. Multiple pieces of evidence indicated that the genetic influence on vegetarianism could be connected to lipid metabolism (energy processing) and its function in brain processes.

• • Firstly, several genetic variations that exhibited an association with vegetarianism have previously been linked to traits related to both lipid metabolism and brain function.

• • Secondly, the gene closest to the only associated genetic variant in the study, TMEM241 has been previously shown to be associated with higher serum triglyceride (a type of lipid) levels. ³

• • Thirdly, other key genes implicated in vegetarianism, including NPC1 (associated with cholesterol transport within the brain) and RMC1, are believed to be involved in regulating key lipids in cell membranes, including cholesterol (a vital lipid) and glycosphingolipids (complex lipids). ⁴ Mutations in NPC1 primarily cause Niemann-Pick disease type C, characterized by the build-up of these lipids within cells, especially affecting the nervous system. ⁵

• • Fourthly, through tissue expression analysis, the study showed that variants associated with vegetarianism may predominantly govern gene expression in the brain.

Four Limitations of the Study 

Does this study imply that genotyping a single variant could predict whether someone is more inclined to be vegetarian or not?

While this study is indeed extensive, involving a substantial number of participants and genetic variants spanning the entire genome, it is premature to derive immediate practical benefits from it. Several concerns need to be addressed. 

#1. Correlation, Not Causation

It is crucial to note that this study establishes a genetic connection but doesn’t imply causation. In other words, these genes may not directly cause vegetarianism; instead, they might be linked to traits or processes that influence dietary preferences. For instance, some genes identified in the study are related to how the body metabolizes lipids, suggesting that certain individuals may have specific lipid requirements that meat fulfills. 

A prospective cohort study, wherein individuals with known genetic profiles are longitudinally observed to investigate their adherence to a vegetarian diet, could offer valuable insights into establishing causality within this context.

#2. Missing heritability

A previous study comparing taste preferences in twins has shown that our taste preferences are highly heritable, with heritability ranging from 20% to 78% depending on the food product. ⁶

Most recently, another twin study reported heritability of refraining from consuming beef, pork, poultry, fish, or shellfish ranged from 70% to 80%. This suggests that our dietary preferences may have a strong genetic component. It’s important to note that a single SNP with a minor influence on vegetarianism does not account for the high heritability observed in this trait. 

In the future, conducting extensive studies encompassing millions of participants holds the potential to discover novel genetic variants. Moreover, the accessibility of comprehensive sequencing data, which includes genotyping of all genetic variants, including rare ones, may contribute to mitigating the issue of missing heritability.

#3. Generalizability to other populations

The study’s results may not be beneficial to populations of non-white individuals, as it primarily focused on a homogenous group of white participants. 

Furthermore, unlike the general population, which typically includes participants with diverse health conditions and economic backgrounds, the majority of participants in this study were relatively healthy and had higher socioeconomic status. Consequently, it’s important to recognize that the study results may not necessarily apply to a broader, more diverse population.

#4. Complex Interplay of Genes and environment

While genetics undoubtedly play a role in our dietary preferences, it’s only part of the intricate web that determines what we eat. Our dietary choices are shaped by a myriad of factors, including upbringing, social and cultural influences, and environmental considerations. 

Factors such as health concerns, moral beliefs, and available food options all contribute to whether someone maintains a vegetarian diet.

Conclusion

Ongoing research may provide insights into whether dietary preferences are innate and extend beyond mere willpower.

In the future, acquiring knowledge about your genetic makeup may help determine if a vegetarian diet aligns with your specific needs.

If you find it challenging to adhere to a particular diet, remember not to blame yourself, as genetics may play a role in dietary decisions.