Think of it this way,” explained zoologist and author Bill Schutt. “Compare it to somebody who has decided that all they’re going to do is eat cows for the rest of their life. They’re not going to eat fruit, they’re not going to eat vegetables, they’re just going to eat meat. Mammal meat. It can be muscle—you’d eat a steak or ribs—or it can be organ meat: a liver, kidneys, etc.
It would be exactly the same.” Schutt, who wrote the book Cannibalism: A Perfectly Natural History, went on: “You’d be getting a lot of protein and fat, no carbs—and very, very few vitamins. Vitamin C, Vitamin D, all the sort of deficiencies that go along with a lack of those vitamins, they become apparent very quickly. Your LDL cholesterol levels are gonna shoot through the roof, you’re probably gonna be lethargic.” (Or, perhaps, you might end up in such precarious health that a shot of apple cider would keep you from sleeping for a month?)
Human flesh can also be unsafe to eat. Even if our hypothetical real-life cannibals would diversify their diet to avoid scurvy, they would still render themselves vulnerable to a whole host of human diseases and bloodborne pathogens. Some of these are serious—bovine spongiform encephalopathy, or Mad Cow disease, has human varieties as well. Kuru, a particularly fatal degenerative brain disorder, has been found among the Fore people of Papua New Guinea, who performed cannibalism as a funerary practice. “It was determined that it was something called spongiform encephalopathy—the closest thing you can think of to that is Alzheimer’s disease. It basically turns your brain into a sponge—there’s holes in it. And this is what happens to you if you eat the flesh of a human, especially from the brains and spinal cord and nerves of somebody who has this disease,” Schutt said.