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I would appreciate it if someone with technical competence assessed the reliability of this study and its findings.

Vegetarianism is mostly genetic, claim Wesseldijk et al.

Jan 17 20242 min read 6

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https://www.sciencedirect.com/science/article/pii/S095032932200180X

I found this topic first from a short snippet in The Week, then from the news article https://www.smithsonianmag.com/smart-news/maintaining-a-vegetarian-diet-might-be-in-your-genes-180983021

According to the twin study of one of the quoted papers, if I don't misunderstand it, 70-80% of abstinence from various animal products can be ascribed to genetic influence, regardless of people's conscious reasons. This is striking to the point that I am initially sceptical. They cite similar results specific to vegetarianism and veganism from another paper in 2021, https://linkinghub.elsevier.com/retrieve/pii/S0950329321003037

I'll confess that my first response wasn't to actually look at the papers- I was in poor mental health and productivity condition at the time. Instead I searched the EA forums to see what the community consensus was on heritable diet preference. But searching 'meat genetics', 'vegetarian genetics' and 'vegan genetics', and those search terms in reverse order, on the EA forums, I saw only one post that used both terms in the immediate search results, suggesting this is not widely discussed here. In that context it was talking about whether EAs have to trade off their health to go vegan. This paper was not cited. https://forum.effectivealtruism.org/posts/3Lv4NyFm2aohRKJCH/change-my-mind-veganism-entails-trade-offs-and-health-is-one?commentId=G7ZK76h99Nrv6GCEq

I have no domain specific knowledge, so I'd like others to weigh in. How convincing are these studies, and what do the results mean from the more general standpoint of animal advocacy?

If there are fixed individual genetic markers that cause people to feel significantly worse after giving up meat and/or dairy, that might be causing a disconnect between veg*ns who say it's easy and ex-veg*ns who claim to- in extreme cases- have almost died, both believing the other side is engaging in motivated reasoning. And perhaps general acceptance of the moral necessity of vegetarian and/or vegan diets is going to be more difficult than we'd thought, barring improved plant-based substitutes that mimic real meat, human gene editing, or some great strides in nutritional science that can isolate the necessary nutrients. I cautiously agree with Singer's stance that even if human nutrition was suboptimal it'd be worth it, but I imagine advocates would struggle to convince a public if a vocal minority were experiencing personal problems from the transition.

As someone new to the forums I don't know how to weight 'these studies are misleading/wrong and everybody already knows' vs 'nobody else has posted this vital info specifically yet' or various points in between. Either way it will be a learning experience.

Summary- these two twin studies claim a person's willingness to stick with veg*n diets, regardless of their stated reasons, are 70-80% inborn. Few people in EA seem to be talking about this topic. If true, it could explain the wildly different accounts of the effect of veg*n diets on health, and presents barriers to making veg*nism normal. I'd like better-informed people with more domain knowledge to weigh in on whether these are good studies and my interpretation is correct.

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Bob Jacobs1y25

I found this topic first from a short snippet in The Week, then from the news article https://www.smithsonianmag.com/smart-news/maintaining-a-vegetarian-diet-might-be-in-your-genes-180983021.

Remove the dot at the end, otherwise it's a dead link.

It is important to note that behavior is always in relation to an environment, so we can't say that some behavior is 70% caused by genetics, the most we can say is that something is 70% caused by genetics in this specific environment. This is easy to check with a thought experiment, lets take these people whose "willingness to stick with veg*n diets, regardless of their stated reasons, are 70-80% inborn" lock them in a vegetarian Hindu monastery and you'll obviously see the rate of vegetarian diets skyrocket. So when you write "Vegetarianism is mostly genetic, claim Wesseldijk et al." Wesseldijk herself would say:

Yet, as Dr. Wesseldijk reminded me in an email, high heritabilities do not imply that biology is destiny. According to surveys by the Vegetarian Resource Group, the percentage of Americans who are vegetarian or vegan jumped six-fold between 1994 and 2022—from 1% to 6%. This impressive change in patterns of meat-eating was due to shifts in cultural attitudes, not changes in our DNA.

And to tie it in to the Hindu monastery (from the same article):

It is important, however, to keep in mind that estimates of heritability only apply to the populations that the subjects in the studies represent. Most of the individual differences in meat-eating among the Dutch are rooted in genes, yet culture is almost entirely responsible for the fact that per capita meat consumption is 20 times higher in the Netherlands than it is in India.

Or as Dr. Wesseldijk has also phrased it:

An environment can completely counteract something that is highly heritable, and the same goes with vegetarianism

Hayven Frienby1y1

Agreed completely. A genetic component influencing dietary decisions doesn't mean that veganism / vegetarianism is out of reach for most or that cultural factors play no role in the adoption of animal-friendly lifestyles. There's definitely still a role for advocacy regardless of the heritability of veg*nism.

Hayven Frienby1y10

As someone who has done vegan advocacy for a long time, this matches with my experience unfortunately. A meatless diet just "clicks" with some people, while with others it's a near impossibility to get them to sustain without meat (let alone other animal products). A genetic component would certainly explain my observations, because there definitely seems to be something deeper than underlying belief or commitment going on.

If anything, this further underscores the need for cellular agriculture (lab-grown meat / eggs / dairy, without harm to animals). We need to find a way to make these foods cheap and cruelty-free, since universal veganism / vegetarianism may not be possible (although there are certainly a lot of cultural barriers that can be addressed first).

Elizabeth1y2

I've talked about this a bit in the post you cited, and happen to have recently commented on it. I haven't dug into the genetics or tried to quantify the effect because I don't expect the data to be very actionable at this stage. We're years from having specific treatments based on genetics, most studies are very bad, and I think self-reports and veg*nism attrition rates should be enough to convince people that people vary widely and you need to plan for that in full generality.

emre kaplan🔸1y0

I would appreciate it if someone with technical competence assessed the reliability of this study and its findings.

Henry Howard🔸1y-1

Doesn't pass the sniff test for me. Two concerns:

Every vegetarian I've met or heard of is vegetarian because of either a) animal welfare, b) climate change or c) cultural tradition. It seems very unlikely that any of these factors could be strongly genetic.
They're determining genetic heritability by comparing identical twin pairs with non-identical twin pairs (i.e. if the identical twins are more similar in their preferences than non-identical twins, they assume that there's more of a genetic component). I imagine that there could be lots of confounders here. Growing up as an identical twin is a different experience to being a non-identical twin. There could be different environmental factors between the two situations (e.g. maybe identical twins tend to feel closer and more closely mimic each other's behaviours/choices).