 In 1853, a bed-ridden vegetarian was reported to experience a remarkable recovery upon eating meat. Probably didn't help, he was an opiomatic, but he had been doing that for a decade. It was only after five years that he was a vegetarian. Did he end up bed-ridden, covered in bed sores? My little beef and mutton he was eventually up and about. Can't blame the poor guy, as this was nearly a century before the discovery and identification of vitamin B12, resulting in just one of six separate Nobel Prizes awarded for teasing out its structure and function. One of the most dramatic events in the history of medicine was the curing of pernicious anemia of B12 deficiency disease and otherwise fatal disorder with a special diet centered around calf and beef liver. Vitamin B12 levels start to drop within months of cutting out meat and yes, there are all sorts of benefits of adopting a more plant-based diet, but underestimating the risk of developing a B12 deficiency nullify the health benefits of a vegetarian diet, or even a diet centered around plant foods but contains meat only a few times a week. Even moderate amounts of animal products may not be sufficient to restore and maintain adequate vitamin B12 function. Vitamin B12 is not made by plants. It's not made by animals either, but rather microbes that blanket the earth. We presumably used to get B12 drinking out of a mountain stream or well water based on studies showing vegetarians in developing countries who drink purified water appear to be at higher risk. But now we chlorinate the water supply to kill off any bacteria so we don't get a lot of B12 in our water anymore. We don't get a lot of cholera either. That's a good thing that we live in such a nice sanitary modern world. Vegetarians living in developing world slums appear to have fewer B12 problems. Basically the more hygienic our meals, the less B12 we get. Our fellow great apes like gorillas get all the B12 they need eating their own feces. I prefer supplements. Before getting into the nitty gritty of how much to take, how frequently a witch type is best, what are the symptoms of B12 deficiency? What aren't the symptoms of B12 deficiency? It's known as the great masquerader. It can cause everything from abdominal distention and chronic diarrhea to shortness of breath and swollen red painful feet. It can also cause Parkinson's syndrome like symptoms skin darkening that resolve with supplementation and something I had never heard of before, bilateral useless hand syndrome. The many faces of B12 deficiency include neurologic symptoms such as numbness and tingling in the hands and feet, muscle cramps, dizziness, cognitive disturbances, difficulty walking, erectile dysfunction as well as fatigue, and psychiatric symptoms like depression and even psychosis. For example, 47-year-old woman with a five-year history of psychosis treated with anti-psychotic drugs, cognitively reporting visual hallucinations, until finally her mother revealed that the patient was following a strict vegan diet for seven years. She started B12 supplements and her symptoms went away. Years of her life lost in a psychotic haze, all apparently because she didn't want to take a supplement. But vitamin B12 supplementation is mandatory for anyone eating plant-based diets. Becoming psychotic is bad, but hey, better than falling into a coma, not to mention suddenly going blind with multiple organ failure, all thanks to B12 vitamin deficiency on a vegetarian diet. Looking into his eyes, they saw exuberant hemorrhages. He was bleeding into his eyes. You don't have to be an ophthalmologist to recognize this is not what the back of your eyes should probably look like.