Gut microbes matter clinically, so diets based on food availability in different markets matter ethically. But that's just one reason to care about food in health care ethics. Providing safe, nutritious, and environmentally sustainable food to all is a great challenge. Physicians in some US cities have been writing prescriptions for patients to obtain fresh produce through healthy food outreach programs. Clinical encounters, however, cannot fully reverse negative health effects of low-quality diets. If the global community cannot find solutions to address food quality and access, costs will be high. This issue investigates some of the compelling ethical issues at stake with food and health.