In a large Dutch twin sample, we found that genetic variance accounted for 74% and 77% of whether people were pescatarian or vegetarian, respectively; the remaining variance was accounted for by non-shared environmental influences

The heritability of pescetarianism and vegetarianism. Laura W. Wesseldijk et al. Food Quality and Preference, August 23 2022, 104705. https://doi.org/10.1016/j.foodqual.2022.104705

Highlights

• Pescetarianism is 74% heritable and vegetarianism 77%.

• Genetic influences account for 70-80% of individual differences in abstinence from eating beef, pork, poultry, fish and shellfish.

• Individuals did not eat pork mostly because of health reasons, poultry, fish and shellfish because of dislike, and beef because of beliefs.

• Regardless of the different reasons for abstinence, heritability estimates were of a similar large magnitude.

Abstract: Genetic factors have a substantial influence on individuals' food preferences, but less is known about their influence on abstinence from eating meat and fish. Here we looked at the influence genetics may have on pescetarianism (not eating meat but eating fish) and vegetarianism (not eating meat and fish) in a Dutch twin sample (N = 8,196). We also examined genetic and environmental influences on abstinence from eating beef, pork, poultry, fish or shellfish separately and explored the reasons individuals gave for not eating these types of meat and fish (e.g., disliking, health concerns or beliefs). Abstinence from eating various meats or (shell)fish varied from 5.3% for beef to 46% for shellfish, and 3.7% did not eat meat (1.9% was pescatarian and 1.8% vegetarian). The prevalence of all abstinences was higher in women than men. Genetic factors accounted for 74% and 77% of variation in pescetarianism and vegetarianism, respectively, with the remaining variance accounted for by non-shared environmental influences. Heritability for abstinence from eating beef, pork, poultry, fish or shellfish ranged from 70 to 80%. Abstention from pork was mostly due to health concerns, abstention from poultry, fish and shellfish because of dislike, and abstention from beef because of beliefs (i.e., religion or convictions). Most pescatarians and vegetarians reported beliefs as one of their reason for abstinence (∼75%). Overall, regardless of the fact that different reasons seem to play a role in pescetarianism, vegetarianism and abstinence from eating different meats and fish, genetic factors undergirded all with a similar large magnitude.

 

See also Where the Rubber Meats the Road: Relationships between Vegetarianism and Socio-political Attitudes and Voting Behavior. John B. Nezlek & Catherine A. Forestell. Jul 15 2019. Ecology of Food and Nutrition, Volume 58, 2019 - Issue 6, pp 548.559. https://www.bipartisanalliance.com/2020/01/possible-genetic-predisposition-to.html

4. Discussion

In a large Dutch twin sample, we found that genetic variance accounted for 74% and 77% of whether people were pescatarian or vegetarian, respectively. The remaining variance was accounted for by non-shared environmental influences. Hence, we detected no effect of the common environment, which should include social transmission from parents and other forms of environmental exposures shared by twins. These results are in line with findings from the recent Finnish study that found vegetarianism/veganism to be 76% heritable (Çınar et al., 2021). We replicated the heritability estimate in a sample of a similar age (Finnish sample M = 29.51 years, SD = 7.84, Dutch sample M = 35.25 years, SD = 15.26), though with a much lower prevalence of vegetarianism. This is, however, roughly in line with country-specific prevalence for vegetarianism (approximately 4-5% in the Netherlands and 11% in Finland) (Motrøen, 2020, van Rossum et al., 2020). Furthermore, we found the degree of genetic influences on abstaining from beef, pork, poultry, fish and shellfish to all be roughly around 70 to 80%. Notably, common environment factors were strongest for abstention from pork (28%), though the influence was non-significant with an alpha of .01 (corrected for multiple testing). In a previous study, the heritability of food preference was explored in the same sample (Vink et al., 2020). The broad sense heritability for liking of meat and fish, measured on a continuous scale, varied between 41% and 60%. This suggests that genetic factors play a larger role in abstinence from eating meat and fish than in the liking of these foods.

Pork was the only type of meat that individuals in our sample abstained from mostly because of health concerns. Beliefs, which was often selected as a reason not to eat particular types of meat (especially for beef and not eating meat), could reflect religion or conviction (in the survey the example given was veganism). We recommend future studies to differentiate the reason ‘beliefs’ and ask in more depth about the specific beliefs or convictions, like type of religion, mitigation, climate change or animal welfare. No information on religion was obtained in the current study. However, information obtained for 79.2% of the sample from one or more other surveys showed that 22% of the sample reported having no religious affiliation, 77.5% reported a religious affiliation at one point in their lives and 0.5% indicated some belief but no affiliation with a specific religion. The vast majority of those ever affiliated with a religion indicated to be Christian or to be raised as Christian and only a small minority indicated affiliations with religions that forbid the consumption of pork, beef, or both. It is therefore unlikely that beliefs reflect the influence of religion. Interestingly, people mostly abstained from poultry, fish and shellfish due to dislike. Some individuals reported 'other reasons' for their abstinence from eating meat or fish. We can only speculate about what those other reasons could be. Given that concerns about animal welfare and environmental sustainability were not among the response options, these 'other reasons' could have reflected such concerns. Additionally, some people might not eat certain types of meat or fish because they are too expensive (like shellfish), although the prevalence of being pescatarian and vegetarian was higher among higher educated participants (with probably higher incomes) than moderate or lower educated participants. Overall, regardless of the fact that different reasons seem to motivate abstention from beef, poultry, pork, fish or shellfish, genetic factors undergirded abstinence from eating all types of meat and fish with a similar magnitude (around 70-80%).

This study has limitations. We made use of self-reports. Whereas participants in the earlier Finnish sample answered yes or no to being vegetarian or vegan (Çınar et al., 2021), participants in the current study were designated as pescatarian or vegetarian based on reporting abstaining from eating specific types of meat and fish. It is possible that, in the Finnish sample, being vegetarian was interpreted as abstaining from eating meat, but not fish, or as abstaining only from certain types of meat. Conversely, some participants in the current study could abstain from beef, pork or poultry, but eat a different type of meat. Further, standard assumptions of classical twin modeling apply here (Verweij, Mosing, Zietsch, & Medland, 2012). Inferences are limited to the population which was approached for the study. The factors underlying vegetarianism in other populations might be different, especially for populations from different cultures, with different religions and/or a higher prevalence of vegetarianism. Lastly, we were initially also interested in investigating environmental and genetic influences on abstaining from all types of meats, fish and dairy (i.e., being vegan). However, our sample included only 20 vegans. Similarly, the majority of pescatarians and vegetarians were female and the data therefore did not allow to investigate sex differences in the genetic architecture. Larger sample sizes are needed to examine genetic influences on veganism, differences between males and females in the heritability of food abstinence, and genetic correlations between abstinence from different types of food. Genetic correlations (with either twin studies or molecular genetic approaches) between vegetarianism and other variables (e.g., education or personality traits) could shed light on the mechanisms underlying dietary choices. We would expect that abstaining for reasons like beliefs with respect to sustainability and animal welfare are more related to genetic factors for personality, while abstaining for reasons like dislike or allergy are more related to genetic factors for more biological processes (for example, genes that code for taste receptors). For this second scenario, we expect that molecular genetic studies will identify genetic variants that shed more light on the underlying biological mechanisms (e.g., genes related to taste, as has been found for coriander abstinence (Eriksson et al., 2012), versus genes related to personality).

To conclude, we confirmed that genetic factors play a large role in individual's choice to be pescatarian, vegetarian or to not eat meat (74-80%) in a Dutch population. Genetic influences on abstaining from beef, pork, poultry, fish and shellfish ranged from 70 to 80%, regardless of the fact that different reasons seem to motivate abstinence from these different types of food. Future research should further investigate genetic correlations and genetic influences on associations between vegetarianism and other psychological traits.