Producing nutritionally literate consumers who can make prudent judgments in today's marketplace is a major goal of nutrition courses for non-majors and interested citizens. It is suggested here that providing information alone is not sufficient and that Piagetian research may provide a useful framework for understanding the reasoning skills that are also needed. Research on adolescent and adult reasoning is at an exploratory stage, and although Piaget's notion of “formal thought” may not account for all adult reasoning, it does seem to involve some skills of importance to consumers. In this study, the reasoning skills of non-major nutrition students were assessed on the basis of their performance on tests derived from the work of Piaget. Only about 25 percent of the subjects used formal reasoning consistently. There was no difference between those who used formal reasoning and those who did not in terms of their ability to comprehend and apply elementary nutrition information. Both types of subjects were also able to carry out, to some degree, tasks in nutrition which were more complex. However, those who used formal reasoning scored significantly better (p < 0.001) than those who did not on tasks which involved analyzing books and ads for their misleading logic, using nutrient labels, and evaluating nutrition issues. Teaching strategies suggested by Piagetian theory resulted in significant gains (p= 0.004) in the use of formal reasoning, whereas the lecture-discussion method did not. Those who teach non-majors are urged not only to provide food and nutrition information but also to encourage the development of the reasoning skills of these student-consumers.