Steady diet of confusion: Contradictory nutrition messages in the public information environment

Nutrition researchers, clinicians, and communication scholars have assumed that contradictory health and nutrition messages exist in the news media, and that exposure to these messages negatively influences public understanding and health behavior. This dissertation does not take issue with these claims, but rather with the evidence base that supports them. Although there is some evidence that contradictory health and nutrition messages exist, serious empirical studies of these messages and their potential effects are scarce. In addition, the few studies that exist lack a theoretical rationale for why contradictory messages might lead to effects. This dissertation moves beyond assumptions by asking two overarching research questions: (1) To what extent do contradictory nutrition messages exist in the news media, and (2) is exposure to such messages linked to potentially deleterious outcomes—namely, nutrition confusion (defined as perceived ambiguity about nutrition recommendations and research), nutrition backlash (defined as negative beliefs about nutrition recommendations and research), and, ultimately, decreased intentions to engage in recommended nutrition- and health-related behaviors? To address these questions, I conducted four studies. Study 1, a content analysis of news media coverage, focuses on the first research question, and Studies 2, 3, and 4—all of which use cross-sectional survey data—address the second question. Results provide support for the claim that contradictory nutrition information exists in the news media. Perhaps more importantly, there is evidence that people notice this information. Measures of media exposure to contradictory messages were developed and validated for the purposes of this research, and results show that exposure is associated with negative outcomes. Specifically, exposure to conflicting information on the health benefits and risks of, for example, wine, fish, and coffee consumption is associated with confusion about what foods are best to eat and the belief that nutrition scientists keep changing their minds. There is evidence that these beliefs, in turn, may lead people to doubt nutrition and health recommendations more generally—including those that are not rife with contradictory information (e.g., fruit and vegetable consumption, exercise behavior). The implications of these findings for communication theory and research, health journalism, and medical research are discussed