Your Vegetarian Diet May Be Making You Sad

An agriculture fair in France. New research suggests that eating only produce could be linked to depression. JACQUES DEMARTHON/AFP/Getty Images

There is no shortage of praise for vegetarian diets, but new evidence suggests that not eating meat could make you depressed.

A team of researchers in the United Kingdom and United States point out there's not much the medical community knows about how plant-based diet plans affect people's mental health. So, they decided to test whether people who identified as vegetarian were more likely to be depressed.

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Using data from an old research study that took place in the U.K. which asked families to report on their diets, the team found that vegetarian males were more likely to be depressed than their carnivorous counterparts. The sample included nearly 10,000 men who had a pregnant partner, and everyone identified their dietary preference. Only 350 reported being vegetarian.

The scientists compared how both plant- and meat-eaters fared on the Edinburgh Postnatal Depression Scale, used by U.K. doctors to determine if women are likely to develop postpartum depression. The team found that vegetarians were more likely to have scores higher than 10, the minimum threshold of possible depression. They report their findings in the current issue of the Journal of Affective Disorders.

The survey ferreted out some honesty about what exactly the participants meant by "vegetarian." Although the men who said they followed such a diet didn't eat burgers or hot dogs, they did consume nearly as much oily fish and shellfish as meat-eaters. And those who identified as vegetarian actually did indulge in red meat: 72 reported some consumption while only 16 of the vegetarians admitted to cheating.

Red meat has vitamin B12, which researchers believe could help alleviate depressive symptoms. Scott Olson/Getty Images

The researchers don't assert that being vegetarian causes depression. Instead, they're suggesting a link between plant-based diets and mental health. The primary theory for this link is that vegetarians receive fewer nutrients found in red meat, vitamin B12 specifically, and that could contribute to depressive symptoms. But the study authors believe this new data should spur a randomized controlled trial to further examine the relationship between meat and mood.

Studies have increasingly shown that nutrition and depression are linked. As researchers noted in a paper from 2008, nutritional neuroscience has just begun looking at how nutrition impacts cognition, behavior and emotion. But many patients with mental disorders have deficiencies in certain nutrients, including omega-3 fatty acids and B vitamins. In a small study of patients conducted in 2013, doctors found that coupling vitamin B12 supplements with antidepressants significantly decreased symptoms.

No word from the researchers on the link between cheating on your vegetarian diet and feelings of regret.