The nuance of a study showing a link between vegetarianism and poor mental health got lost as the study was shared widely online, reports Business Insider.
Previous research shows an association between vegetarianism and a higher risk of depression and anxiety, according to the study, a systemic review of 18 other studies on meat consumption and mental health.
A team of researchers from the department of psychology at the University of Southern Indiana found that 11 of the papers suggested meat eaters had better psychological health than vegetarians. Of the remaining 7 studies, three showed that vegetarians had better mood or mental health symptoms than meat eaters, and the other four had mixed results. The researchers concluded that there is "clear evidence that meat-abstention is associated with higher rates or risk of depression, anxiety, and self-harm."
However, the report says, it's not so clear-cut.
Dr Edward Archer, a co-author of the study and chief science officer for the data analytics firm Evoving FX, is quoted in the report as saying that the research does not show that meat can improve mental health, or that avoiding it can cause mental health issues. "We were very careful to say no causal inference should be made. We offered lots of information for both sides of the debate," he said. "We cannot say that meat-free diets cause mental illness. What we did find is that the research doesn't support the idea that eliminating meat can improve mental health."
But, the report says, that nuance got lost as the study was shared widely online.
The study didn't actually show that a meat-free diet causes depression or other mental health issues but several media publications reported the research as showing that meat improves mental health outcomes.
Archer said that's not an accurate portrayal of the study. "That's patently false, you can't make that statement. We did not claim that," he said.
According to the report, epidemiologist Gideon Meyerowitz- Katz said on Twitter that the research shows that there may be a relationship between vegetarian and depression and/or anxiety, but it doesn't prove that eating a meat-free diet causes those issues. In fact, one of the main studies included in the analysis found that some of the vegetarians had started a meat-free diet after being diagnosed with depression.
Archer said there could be many factors to explain the link the study found between mental health and vegetarianism. A few possible explanations could that people try vegetarian diets to address existing health issues, or that people who are sensitive to ethical issues may be more likely to be both depressed and vegetarian.
"What we've shown clearly is that there's some relationship. There's a million ways of looking at this – individuals who are suffering from depression and anxiety will treat themselves with changes in dietary patterns," Archer said. "Or, individuals who are very sensitive to the suffering of others may take an ethical stance, and if you look at the amount of suffering, those people may become depressed and anxious because of that." What the researchers actually conclude is that a vegetarian diet probably doesn't make depression or anxiety any better.
"Our study does not support meat avoidance as a strategy to benefit psychological health," the authors wrote.
The report says an important take away, according to Dr Wendy Bazilian, a registered dietitian with a doctorate in public health, is that diet and psychological health are clearly related. This kind of research can help us better understand that relationship, and make choices according to our unique circumstances and preferences, she said.
"I think there is some strength to what the study suggests that we need to look at that, whether you're a meat eater or not, maybe there isn't a one-size-fits-all," Bazilian is quoted in the report as saying. "I think some next steps are to make sure we're looking at nutrients that may be of concern to mental health, and checking in with mental health of our patients regardless of what diet they follow."
The report says Meyerowitz-Katz also notes a glaring issue with the study: that it's funded by the meat industry. The paper states it was "funded in part via an unrestricted research grant from the Beef Checkoff, through the National Cattlemen's Beef Association."
Archer, who said he was not involved in that grant for the study, said the funding was primarily used to pay student researchers, and that it did not influence the design or analyse of the research. He added that all of the studies his team reviewed were funded by public health, not industry organisations. "I think it's a legitimate point to look at the funders, but you have to make that next step to see if something was done wrong and if funders caused that," he said.
Bazilian agreed that it's not uncommon for industry funding to be involved in nutritional studies. While it's important to be aware of, it doesn't necessarily mean the research is flawed, particularly if the funding is transparent.
"Funding is a slippery slope and you definitely have to pay attention. Industries that have a vested interest want to know what the research says," she said. "It's important to important to know that and look beyond one study, even a review. I don't think that any one study is ever going to be the bottom line on a topic."
[link url="https://www.businessinsider.in/science/health/news/there-are-serious-problems-with-a-widely-shared-study-that-claimed-meat-eaters-have-better-mental-health-than-vegetarians/amp_articleshow/75588467.cms"]Full Business Insider report[/link]
[link url="https://www.facebook.com/drgarth/posts/3101150809905806?tn=-R"]Dr Garth Davis points out some other flaws in the research methodology[/link]
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