The Vegetarian and the Puzzling Link Between Diet and Mood

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Critics have struggled with what to make of Han Kang’s The Vegetarian, an oblique South Korean novella honored with this year’s Man Booker International Prize and, in December, a spot on the New York Times’ “10 Best Books of 2016” list. Through the perspective of the protagonist’s husband, brother-in-law, and sister, Kang chronicles the psychological breakdown of a repressed housewife named Yeong-hye — a mental crisis that kicks off when she announces her decision to become a vegetarian, infuriating her traditional, meat-loving Korean family. As Yeong-hye’s grip on reality weakens, her diet becomes increasingly restrictive; she ultimately reaches the brink of starvation and becomes convinced that she is actually a tree. No one knows quite how to interpret the story — Slate’s Laura Miller suggests readers keep in mind that “Sometimes, how a book or a film puzzles you … is the main point” — but one point of critical consensus is that the title is misleading. “The Vegetarian is by no means a book about vegetarianism or the people who practice it and why,” writes Miller. “… This novel is not about vegetarianism,” according to The New York Review of Books.

There are many plausible factors in Yeong-hye’s descent into madness: her callous husband, her bullying father, a sexist culture. Yet readers might consider whether vegetarianism itself could, in fact, play a role in a breakdown like hers. The effects of vegetarianism on the mind have not been as thoroughly explored as its impact on the body, but an emerging literature on the relationship between diet and mood is somewhat worrying: A handful of studies has found a link between a meatless diet and mental issues like depression, anxiety and self-harm. Vegetarians — a group that skews young, female, and single — may be prone to depression by virtue of demographics, and researchers haven’t definitively distinguished between correlation and causation. But a nutrient-deficient plant-based diet might create problems that contribute to psychological disorders.

“If one removes meat from the diet and doesn’t replace the iron, zinc, B vitamins, and protein, then it is plausible that it may result in depression and/or other medical conditions,” says Felice Jacka, director of the Food and Mood Centre at Deakin University in Australia. “Low iron is definitely associated with fatigue and depression, so depression as a result of vegetarianism may be a function of anemia.”

One large study, which examined national health data on 9,000 young Australian women, found that both lacto-ovo (dairy- and egg-eating) vegetarians and “semi-vegetarians” (who avoided red meat) had higher rates of depression, insomnia, and self-harm, in spite of their superior physical habits — they were more likely to exercise regularly and maintain a healthy body weight.

Gary Wenk, author of Your Brain on Food: How Chemicals Control Your Thoughts and Feelings, compares adopting a vegetarian diet to playing “dietary roulette with one’s mental health.” A psychology professor at Ohio State University, Wenk says he’s watched many of his students, over the years, give up meat without adjusting their diets to include other sources of protein. “The consequence was always the same,” he said. “Depression and anxiety.” He pins the blame on a shortage of tryptophan — an amino acid essential for the synthesis of serotonin, and most easily found in meat — in many vegetarians’ diets. “The body’s store of this amino is not great, and within a short time serotonin production decreases, leading to the anxiety and depression,” Wenk says. (Vegetarians can get tryptophan from foods like nuts, tofu, and cheese.) Women, he notes, are especially susceptible to tryptophan depletion.

A 2012 study by a group of German psychologists explored patterns in meat consumption and mental health among more than 4,000 adult respondents to a national survey. The researchers divided the sample according to diet: “complete vegetarians,” who abstained from meat and fish entirely, accounted for 1.3 percent of the total; “predominant vegetarians,” who ate meat only occasionally, made up 4.6 percent of the group; and the rest were nonvegetarians.

After noticing a handful of socio-demographic patterns that could affect their results – vegetarians tended to be younger and to live in cities — the researchers created a control group of nonvegetarians that was matched for “variables known to be associated with mental disorders (sex, age, educational level, marital status, urban residency).” They then compared the vegetarians with demographically similar omnivores, and discovered that the non-meat-eaters had a much higher incidence of mental problems. Complete vegetarians were more than twice as likely as nonvegetarians to suffer from anxiety, and slightly more prone to “somatoform disorders” (characterized by pain with psychological origins). Their rates of depression were nearly 15 percent higher than those of nonvegetarians, with the semi-vegetarians falling between the other two groups. Even nonvegetarians with mental disorders tended to eat less meat than their psychologically healthy peers.

The authors suggest a number of explanations for the link between mental illness and a meat-free diet, not all of which are causal. One possibility is that a nutritional inadequacy — a deficiency in vitamin B12, which is mainly found in animal products, or of long-chain n-3 fatty acids, which humans usually ingest through fish — could have mental or cognitive ramifications: “[N]utrition status resulting from vegetarian diet may affect neuronal function and synaptic plasticity,” they write, “which in turn influences brain processes relevant for onset and maintenance of mental disorders.” Another is that people adopt a vegetarian diet in an effort to ameliorate some physical problem, which could in turn take a toll on mental health. Some separate social or psychological factor might underlie both vegetarianism and mental illness: People who renounce meat may be more prone to self-denial, or more at odds with the mainstream culture. Or perhaps people who empathize with animals are more sensitive to pain in general, others’ as well as their own. Yeong-hye never offers a coherent explanation for her sudden dietary change, but it seems to be partly driven by her overidentification with the suffering of animals. “I ate too much meat,” she berates herself, apparently overwhelmed by guilt. “The lives of the animals I ate have all lodged there. Blood and flesh … their lives still stick stubbornly to my insides.” (Some of history’s most famous depressives were also highly attuned to animal welfare, if not vegetarian. Abraham Lincoln, who suffered two near-suicidal breakdowns, told his stepsister “that an ant’s life was to it, as sweet as ours to us.”)

These results may be alarming, but they are also preliminary — and scientists say it’s too soon to draw a direct connection. “There is so much that we do not understand about food and its components and the importance of these for our functioning,” says Jacka.

In these studies, “causation versus correlation is not always teased out very well,” says psychiatrist James Gordon, founder of the Center for Mind-Body Medicine, who calls the literature “a bit crude.” Nonetheless, he advises vegetarians to take precautions — such as B12 supplements and “large doses of flaxseed and chia seed,” which contain the omega-3 fatty acids more often found in fish. Vegetarians experiencing mood problems might consider getting blood tests to check their B12 and iron levels. “If you’re going to be a vegetarian, you have to be more thoughtful about what you eat,” he says. “If you’re not, then you’re vulnerable to a variety of physical and psychological disturbances.”

The Vegetarian and the Puzzling Link Between Diet and Mood