Partner Sarah Roller authored the chapter, "Nutrition, Health Policy, and the Problem of Proof" in the book Nutrition in the Prevention and Treatment of Disease, Third Edition. Both the establishing of nutrient intake recommendations and the ability of food producers to make health claims depend on development of an evidence base that links nutrient intake levels to specific health outcomes. The rules of evidence currently employed were developed for drugs and the treatment of disease. They are ill-suited to evaluating nutrients, the function of which is not treatment but health promotion. Moreover, a randomized controlled trial designed to establish a particular nutrient benefit requires that the control group be malnourished—that is, develop the disease outcomes associated with inadequate intake. Doing this is ethically impermissible. Advancement of nutrition at the policy level requires new approaches to determining optimal intake levels. Such alternative approaches include redefinition of "normal" for nutrients, the use of multisystem global outcome indices, and a modification of the non-concurrent cohort study design that avoids the ethical barrier of a controlled trial but still permits reasonably strong inference.