The nuclear accident in Fukushima triggered a process of regulatory action, inspections, and market restrictions that has deeply affected the Japanese food market. When higher than permissible levels of radioactivity entered the food chain, the Japanese Government had to take strong measures to protect consumers. At the same time, it had to explore ways to avoid disproportionate penalties on the producers from the affected region. This article examines Japan's regulatory response to the nuclear accident and the legal instruments the government accordingly employed. Our analysis follows four regulatory steps that were taken by the government to safeguard the food chain: the establishment of maximum permissible levels for radioactive levels in food; the adoption of guidelines on how to monitor these levels; the restriction of the distribution and consumption of excessively contaminated food and, finally, where and when possible, the lifting of these restrictions. This article discusses how the Food and Drug Administration has come to adopt informal guidance (agency advice that influences regulated entities but does not carry the force and effect of law) as its primary method of policymaking, as opposed to more formalized procedures like notice-and-comment rulemaking or case-specific adjudication. Using major developments in administrative law and modifications to FDA's regulatory regime as milestones, the article traces how and why FDA's use of informal guidance to fulfill its statutory mandate has changed over the past century. Along the way, the article identifies important doctrinal questions that persist today, namely (1) whether informal advisory opinions bind FDA and (2) the degree of judicial deference guidance documents should receive under the Supreme Court's decisions in Chevron and Mead. The article attempts to resolve these doctrinal ambiguities. It then undertakes a normative analysis of FDA's increasing reliance on informal guidance, and conclude that, on the whole, this development has benefited FDA's major stakeholders: regulated entities, the general public and the agency itself. The article closes with modest proposals for reform. The article features an appendix with several tables illustrating FDA's output of informal guidance documents by year, to facilitate further study.