Overconfidence in nutritional knowledge is linked to unnecessary gluten-free consumption.

The rising consumption of gluten-free products among non-celiac individuals represents a burden for society due to these foods' lower nutritional quality, poorer taste, and higher cost. While these products are essential for individuals with celiac disease, an increasing number of consumers are choosing them for perceived health benefits. Indeed, subjective beliefs about food and nutrition significantly influence food choices, whether or not they align with scientific evidence. This study investigates the Dunning-Kruger effect within the domain of nutritional knowledge and its impact on consumer behavior. Here we show that individuals with low nutritional knowledge who overestimate their competence-a hallmark of the Dunning-Kruger effect-are more likely to consume gluten-free products without medical necessity. This overconfidence is compounded by narcissistic traits and is further associated with higher conspiracy beliefs about the food industry. These consumers appear vulnerable to marketplace exploitation, lacking the knowledge to make informed food choices while being unaware of this condition. Our findings emphasize the need for targeted communication strategies to guide consumers towards more evidence-based dietary choices, recognizing that fact-based interventions may be ineffective for those with high knowledge overconfidence.