When I was in high school, I ran cross country. One fall, I mysteriously became slow. I felt like a video game character suddenly stuck on a harder setting. My coach insisted it must be mental; I tried pushing harder. Winter track season came, and nothing improved. Then, I tested positive for anemia and started taking iron supplements. By spring, I was back to running my fastest mile time yet.

Deployed correctly, vitamins can feel like magic. Their discovery is littered with stories like mine, in which these mysterious little components of food are shown to wield deep control over flesh. One of the first hints that food could contain such specific components with such specific influence over well-being came in 1816, when experimental physiologist François Magendie fed dogs a diet that was high in sugar and free of animals and plants. The dogs developed sores on their corneas and died. In the 1880s, Dutch physician Christiaan Eijkman studied a flock of chickens that had a tendency to wobble, fall over, and become unable to move; when he switched their diet from plain white rice to rice with husks (brown rice), they recovered. Lacking a modern conception of nutrition, Eijkman assumed that the white rice must somehow be toxic and that the husks were counteracting the bad stuff... [ read more ]