All Species’ Nutritional Needs Are Not Created Equal
Back in the Age of Exploration, the sailors on long sea voyages often died of scurvy. Yet the rats on the ship stayed perfectly healthy. So did the ship’s cat. The sailors quickly recovered their health if they could get some fresh fruit or vegetables to eat. The hard part was finding some form of fresh fruit or vegetable that could be stored on board without spoiling. Eventually, the British Royal Navy figured out that citrus fruit worked well, which is why British sailors came to be called “limeys.” Bean sprouts or alfalfa sprouts would also have worked, but nobody thought to try them.
The mystery of why people can get scurvy, and rats can’t, wasn’t solved until the 20th century, with the discovery of vitamin C, which is found in fresh fruit and vegetables but not in the bread (“hardtack”) that the sailors were being fed. Human beings, along with gorillas and other apes and monkeys, have lost the ability to make their own vitamin C. Guinea pigs have the same problem. In nature, primates and guinea pigs rarely get scurvy, because their natural diet includes plenty of fresh plant material.
Although rats need to have vitamin C in their bodies, they can make their own supply. They don’t have to get it from their food, as people, other primates, and guinea pigs must. That’s why vitamin C is considered to be an essential nutrient for human beings—and for gorillas—but not for rats.