Nothing divides opinions over diet quite like vegetarians. Is it the moral choice? The ethical option? Or, as I was once informed while travelling through rural Spain, is it “not an option that appears on this menu”?* However you define it, and whether you yourself eat meat of not, the one thing we can say is that a lot of people have oddly strong opinions about whether a total stranger has bacon or halloumi for brunch.
Which means that any time a story comes out looking at vegetarianism and health, we leap on it with a heated fervor. This week has been no different — after a study came out looking at vegetarianism and depression, media sources from across the globe immediately started reporting that vegetarianism was terrible for your health. The Daily Mail went so far as to suggest that eating meat in and of itself could improve your mental health, which is great news if you really like cheap steak Tuesdays at the local pub.
The problem is, none of these headlines were even remotely true. The science didn’t find that vegetarianism caused depression, and there’s no reason from this research to believe that meat does anything positive for your mental health at all.
Confused? Let’s look at the science.
The study that everyone has been referring to is what’s known as a systematic review. Basically, the researchers combed through the literature to find every study run on a topic, and then compiled them all into one narrative to get the best evidence possible on a topic. In this case, that topic was the association between vegetarianism and depression.
After collating all of the results looking at this question together, the researchers found something relatively boring, which is actually quite common in systematic reviews of this type: there isn’t enough good-quality evidence to make any conclusions. Specifically, there’s no evidence that vegetarianism causes depression, and at best some weak and spotty evidence that people who are vegetarian may be more likely to be depressed than those who aren’t, but it’s likely this is because some depressed people stop eating meat.
Which is pretty much entirely the opposite of what most papers reported. Strange, that.
There are also some quite odd inconsistencies with the research when you start reading it. For example, even though most of the included research was about comparing vegetarians with meat-eaters, and not the benefits of meat per se, the title mentioned meat twice and never referenced vegetarianism. The authors also appear to have used a very strange scoring system to rate trials, that allowed them to describe a survey run in 1998 including just 54 vegetarians as the best-quality evidence out there on the topic. Even if it is the best evidence, when you read it, the findings of this particular study appear to somewhat contradict the conclusions of the systematic review itself.
It’s very strange. If it’s the “best quality”, and seems to disagree with the systematic review conclusions, then why do we have any confidence in any of the findings of this review?
If you scroll down past the research methodology, results, past the conclusion that says “our study does not support avoiding meat consumption for overall psychological health benefits”, and past the disclosure statement saying that “No potential conflict of interest was reported by the author(s)”, you get this gem right at the very end of the page:
Yes, you see despite there being, apparently, no conflicts of interest, the study was funded via an “unrestricted grant” from Big Beef, in this case the National Cattlemen’s Beef Association. Shockingly, the study funded by people who financially benefit from meat being portrayed in a positive light found that meat might be good for you.
I can almost hear the collective gasp of astonishment.
Now, while I don’t want to unfairly malign the authors, it’s hard not to be a bit skeptical. The review’s main finding was really that there is no evidence that vegetarianism does anything bad for your mental health, but this was headlined in most newspapers as “Eat more meat, get happier”. At a certain point, you have to be a bit suspicious that the researchers were aware that running a review specifically for the meat industry might result in vegetarianism being unfairly maligned.
And the thing is, systematic reviews can be very open to bias from the authors. The data stays the same — in this case, the included studies — but how that data is interpreted and analysed is largely up to the researchers involved. There are numerous methods to guard against this, the most rigorous being from the Cochrane Collaboration, but even these don’t guarantee that you’ve got an unbiased answer at the end — although, if the authors of this paper had used the Cochrane recommended methodology, it’s likely they would’ve come up with a very different answer indeed.
So, no, vegetarianism isn’t going to give you depression. In fact, a much more comprehensive systematic review from 2019 concluded almost exactly that — vegetarianism may help with weight loss/diabetes/heart disease, although this is mostly in comparison to the standard ‘bad’ diet, but there’s no good evidence that it either helps or harms in terms of mental health.
In other words, vegetarianism is almost identical to most other diets out there, except with more tofu involved.
Eat meat if you want to. Avoid it if that’s your choice. Just don’t base your decisions on headlines about studies funded by Big Beef that in reality tell us almost nothing at all.
Vegetarianism may not make you wonderfully healthsome, but it probably isn’t killing you either.
You can also listen to me host the fantastic Sensationalist Science podcast here:
*This was actually quite a funny story, because I was travelling with someone who spoke no Spanish, all I spoke was English and French, and communicating “vegetarianism” through hand gestures took quite a bit of time and creativity.