There is ample evidence that eating a plant-based diet affords numerous health benefits.
But what about a plant-only diet? A brand-new study adds to the evidence that a purely vegetarian or vegan diet seems to be linked to an increased risk of depression.
The link is not clear-cut, however, and there is disagreement about whether vegetarianism causes mental illness or is simply associated with it. Still, that association is fairly strong.
In the new study, to be published in the January 2018 issue of the Journal of Affective Disorders, nearly 10,000 male partners of pregnant women were asked about their eating habits and given depression screening tests. Men identifying as vegetarian had significantly higher depression symptoms, on average, than non-vegetarians.
[See: Am I Just Sad — or Actually Depressed?]
This is the first large epidemiological study to quantify this relationship, according to lead author Dr. Joseph R. Hibbeln. He is the acting chief of the Section of Nutritional Neurosciences in the Laboratory of Membrane Biophysics and Biochemistry at the National Institutes of Health. “This is not a perfect study,” says Hibbeln, who is also a captain in the United States Public Health Service. “It is an association. It doesn’t say that a nutritional deficiency definitely caused depression. It could be that those more predisposed to depression decided to become vegetarian. Also, pregnancy can be a very stressful time,” he adds, and stress plays a more proven role in depression.
Despite these caveats, this is not the only study to note this link. Other analyses have shown that vegetarians and semi-vegetarians are more likely to suffer from several categories of mental illnesses; for instance, they are twice as likely to have had an anxiety disorder and five times more likely to have suffered from an eating disorder. In addition, the occurrence of mental illness among semi-vegetarians generally falls somewhere between full vegetarians and meat eaters, further suggesting some direct connection.
According to large-population epidemiological studies, vegetarians and vegans use more mental health services and report more mental health problems, says Dr. Drew Ramsey, an assistant clinical professor of psychiatry at Columbia University and co-author of “The Happiness Diet” and other books that explore nutrition and mental health. And, Hibbeln says, it is well known that the extreme vegetarianism that has been practiced in some cultures for generations is linked to biological abnormalities that can cause children to be born with severe neurological deficiencies. “Given the well-established case for extreme deficiencies causing extreme problems, we want to know more about less extreme cases,” he says.
[See: 11 Simple, Proven Ways to Optimize Your Mental Health.]
Important Nutrients Lacking
Ramsey calls Hibbeln “the grand general in the brain food army,” but even Ramsey is a taken aback at this study. “It is very surprising because vegetarian diets are generally healthy,” he says. “We promote plant-forward diets, which have more nutrition and fewer calories. But when you exclude seafood and meat, you exclude nutrients that are more accessible and concentrated and some that are more central to the brain’s health.”
The prime suspect in this deficiency is vitamin B12. This vitamin is nearly impossible to come by in just plants, but it is critical for maintaining proper brain function. Without it, “your brain just shrinks faster,” Ramsey says. “There is no controversy about this in the science.” Hibbeln adds that, “There is rock-solid evidence that people on vegetarian diets who don’t supplement become deficient in B12. This is so well-known and tied to depression and mental illness that it is tied to recommended daily intakes.” In the elderly, a B12 deficiency is one of the first things to be ruled out as a cause of dementia, he says.
Vitamin B12 isn’t the only missing ingredient from a vegetarian diet necessary for a healthy brain. Iron is a critical brain nutrient, Hibbeln says, and zinc is also important. Omega-3 fatty acid, found most often in fish, is another “reasonable biological candidate,” he says. In fact, over the past 25 years or so, Hibbeln has conducted some of the most important studies linking omega-3s with depression and other health issues — studies that played a large role in changing the dietary guidelines for all Americans in recent years. “I am a fish pusher,” he says. “Fish is a good gateway.”
[See: U.S. News’ 38 Best Diets Overall.]
Supplementation Is Critical
But even fish may not be enough. Another recent study, published in the journal Alcoholism Clinical and Experimental Research and also led by Hibbeln, followed about 14,500 pregnant women and their children for almost 30 years. The researchers looked at whether moms’ dietary choices during pregnancy would be linked to substance abuse issues in their children later in life. “We thought a deficit of fish would do that,” he says. “But we were wrong.”
The data showed children of moms who ate a vegetarian diet had a “markedly increased” risk of substance abuse, and that was “solely due to a lack of meat, not to other food groups,” Hibbeln says. There was even a so-called dose-response relationship: The more meat consumed, the lower the risk for substance abuse.
Digging deeper, the researchers were able to pinpoint a specific nutrient in meat that transports B12 through the body. “It is a special truck that picks up the vitamin at the loading dock and delivers it to the brain,” he says. “This helped us nail it to B12 deficiency, rather than a cultural or social construct.”
All this evidence doesn’t mean vegetarians should head immediately to their nearest steakhouse. Most nutrition experts believe a plant-forward diet is still the best choice for overall health. It just means that those who eschew all meat and fish must be careful and take supplements to ensure they’re getting enough B12 and the other nutrients necessary for brain health.
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What Are the Risks That Vegetarianism Can Help Trigger Depression? originally appeared on usnews.com
