More and more women are vegging out...of their minds. New research suggests that along with shedding pounds, slashing cancer risk, and boosting life expectancy, vegetarianism could come with lesser-known side effects: Panic attacks. OCD. Depression. WH investigates the puzzling blow of going meatless—and how to stay plant-based without going mental.

Her symptoms were sudden and severe. Drew Ramsey's 35-year-old patient had always been fit and active, but her energy had flatlined. When she did manage to drag herself to the gym, it didn't help. She felt anxious and was often on the verge of tears for no reason, even when she was with friends. Worst of all were her panic attacks, a rare occurrence in the past but now so common that she was afraid of losing her job because she had trouble getting out of bed, and she'd become terrified of taking the New York City subway.

Ramsey, a Columbia University professor and psychiatrist with 14 years of experience, wanted to put her on medication. His patient demurred. She was so conscious of what she put in her body, she'd even given up meat a year ago, having heard about all the health benefits of vegetarianism. So Ramsey prescribed something else: grass-fed steak.

It may sound like an episode of House, but Ramsey had a hunch. He'd seen a dramatic link between mood and food before (he even researched it for his forthcoming book Eat Complete), and guessed that his patient's well-intentioned meat-free diet was the very thing causing her mental deterioration. Sure enough, six weeks after adding animal protein back onto her plate, her energy rebounded and her panic attacks dropped by 75 percent.

Her case is far from unique. "I hear from vegetarians every day; they have this terrible depression and anxiety, and they don't understand why," says Lierre Keith, author of . "People think they're eating a beautiful, righteous diet, but they don't realize there's a potential dark side."

It's true that many of America's estimated 8 million vegetarians are drawn to the diet's promise of a healthier weight, heart, and planet. They pass on beef, poultry, and pork, unaware that a growing body of research suggests a link between going meatless and an elevated risk for serious mental disorders.

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Garden State

Paleo aside, it's been decades since meat eating has been considered truly healthy. Practically every day, it seems, a new study emerges showing that vegetarian diets are the key to everything from shedding pounds to beating cancer. One group of California researchers even found evidence that ditching meat can tack more than three years onto your lifespan.

The plant-based love has gone well beyond medical opinion—it's become part of a cultural shift. Some 29 million U.S. adults now take part in Meatless Monday. Amazon alone has more than 7,000 vegan cookbooks in its inventory (60 of those are best sellers). Open Table has scores of "top restaurants for vegetarians" lists, highlighting star chefs experimenting with zero-meat meals. Even chains like Wendy's and White Castle are grilling up veggie burgers.

"I hear from vegetarians every day; they have this terrible depression and anxiety, and they don't understand why."

It's tough to argue with the science—and with a movement that's been endorsed by everyone from Gandhi to Beyonce. And it's natural to assume that peak mental health and a perpetually blissed-out attitude are just two more side effects of the glowing vegetarian lifestyle.

So it was startling last year when Australian researchers revealed that vegetarians reported being less optimistic about the future than meat eaters. What's more, they were 18 percent more likely to report depression and 28 percent more likely to suffer panic attacks and anxiety. A separate German study backs this up, finding that vegetarians were 15 percent more prone to depressive conditions and twice as likely to suffer anxiety disorders.

Even the pros find the stats confounding in a chicken-or-egg way. "We don't know if a vegetarian diet causes depression and anxiety, or if people who are predisposed to those mental conditions gravitate toward vegetarianism," says Emily Deans, M.D., a Boston psychiatrist who studies the link between food and mood.

Most likely, says Deans, there's truth to both theories. People with anxious, obsessive, or neurotic tendencies might be more inclined to micromanage their plates (in one study, vegetarians had triple the risk of developing an eating disorder compared with meat lovers). Yet experts all agree that, regardless of where you rank on a scale of 1 to OCD, what you swallow plays a major role in what happens in your head.

"Food is a factor in mental health," says Ramsey. "We should be talking about it. You can't just make a sweeping change to your diet and expect it won't have any effect on you mentally."

These "healthy" foods are actually bad for you:

Risky Nutrition

Quick: Name some "brain foods." Well, there's avocado. Olive oil. Nuts. Red meat? Not so much. Yet anthropological evidence shows that, long before we could choose to subsist on cashew cheese and tofu, animal flesh provided the energy-dense calories necessary to fuel evolving cerebellums. Without meat, we'd never have matured beyond the mental capacity of herbivores like gorillas.

Today, stronger brains are still powered by beef—or at least, by many of the nutrients commonly found in animal proteins. At the top of the list are B vitamins, which your noggin needs to pump out neurotransmitters such as glutamate; low levels of it have been linked to depression, anxiety, and OCD (sound familiar?). Similarly, meager levels of zinc and iron, two nutrients far more prevalent in meats than veggies, may manifest as moodiness—or worse. "I've had vegetarians come in thinking they're having panic attacks when it's really an iron deficiency," says Deans. Without iron to help blood shuttle oxygen around, the brain gets less O2, leaving it sluggish and more prone to misfiring. Then there's tryptophan, an essential amino acid found almost exclusively in poultry. Your body can't make it on its own and needs it to produce serotonin, a hormone that acts as the brain's natural antidepressant.

"Today, stronger brains are still powered by beef—or at least, by many of the nutrients commonly found in animal proteins."

Some vegetarians inadvertently dig themselves in deeper by filling up on white bread, rice, and pasta; sugar-laden cereals; and cookies. This so-called carbitarian diet is free of meat but rich in problems, says internist Vincent Pedre, M.D., author of Happy Gut. "The resulting seesaw of blood sugar and hormone levels may lead to even more irritability, depression, and anxiety."

Meat in the Middle

Of course, plenty of vegetarians never experience so much as a single mental-health hiccup, and savvy ones are able to eat around the aforementioned nutritional deficiencies (see "Eat Your Feelings," page 143). Clearly, it's possible to adjust to, even thrive on, a meat-free existence.

But quitting meat shouldn't be done cold turkey, cautions Deans. Consult a nutritionist or doctor beforehand, especially if you're susceptible to mood disorders or have a family history of them. Then cut down gradually. "Start using meat as a garnish in a dish rather than as the main attraction," suggests Diana Rice, R.D., a dietitian in New York City. Other healthy ways to lean in to veggie-based eating: Scale back to just one meaty meal per day; nix meat only on weekends or certain weekdays; or practice flexitarianism—the term for when you eat meat only on occasion, or don't do meat but still eat dairy, eggs, and fish.

As you go, keep tabs on how you feel, physically and mentally. "Everyone responds to going vegetarian differently," says Rice. "Some feel amazing right away, some may feel the same, and some realize they're better off with a little bit of animal protein in their diets after all."

Isabel Smith, 27, was one of the latter. Just like Drew Ramsey's patient, she was active and energetic and thought a vegetarian diet was the perfect complement to her health-conscious lifestyle. But after a few weeks sans meat, she found herself uncharacteristically weepy. "I was tired and frustrated and got upset more easily, especially over things that wouldn't normally bother me," she says. "I would find myself sad for no reason." Shortly after she started eating meat again, she noticed an uptick in her mood.

The twist? Smith is a registered dietitian. One who now understands personally what she studies professionally: Not everyone is cut out for a life without meat. For many people, it's crucial to realize that the emphasis in food writer Michael Pollan's oft-quoted advice to eat "mostly plants" shouldn't always be on the second word.

Learn which meat substitutes are our favorite and get other healthy-eating tips in the December issue of Women's Health, on newsstands now.

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