Apart from their actual health benefits, vitamins have played an important role in the American consciousness as the arena for a struggle between competing systems of knowledge: the positivist authority of "normal science" with its controlled experiments and research protocols versus the anecdotal evidence and personal experiences of ordinary consumers. Since antiquity, it has been commonly known that there is a connection between diet and health, but it was not until the early 1900s that specific vitamins were isolated and accepted by the public as essential to our well-being. What began as an exercise in public health became big business: by the end of the century, retail sales of vitamins in America exceeded $3.5 billion, with surveys showing more than 40 percent of Americans using vitamins on a regular basis. The story of vitamins demonstrates, in the words of social historian Rima Apple, that "Science is not above commerce or...