In 1973, San Francisco allergist Ben Feingold created an uproar by claiming that synthetic food additives triggered hyperactivity, then the most commonly diagnosed childhood disorder in the United States. He contended that the epidemic should not be treated with drugs such as Ritalin but, instead, with a food additive-free diet. Parents and the media considered his treatment, the Feingold diet, a compelling alternative. Physicians, however, were skeptical...