“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,” “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.