Adherence to the Mediterranean Diet and Sustainable Nutrition: The Role of Nutrition Literacy Across Generations

Background: Sustainable diets, particularly the Mediterranean diet, are associated with improved human and planetary health. Nutrition literacy influences food choices, yet intergenerational differences in literacy and adherence to sustainable diets remain underexplored. This study examined the relationship between nutrition literacy, adherence to the Mediterranean diet, and sustainable nutrition behaviors among Generation X, Y, and Z adults living in Istanbul. Methods: A cross-sectional online survey was conducted among adults aged 18–60 years. Data were collected through a demographic questionnaire, the E-Healthy Nutrition Literacy Scale, and the Short Questionnaire for Mediterranean Diet Adherence and Sustainable Nutrition. Parametric statistical analyses were performed. Results: Among 1395 participants, adherence to the Mediterranean diet did not significantly differ by generation or gender (p > 0.05). Participants with prior nutrition education were significantly more likely to achieve high nutrition literacy scores and adhere to sustainable eating practices. Adherence to sustainable nutrition increased across generations, with Generation Z exhibiting the highest proportion of low adherence (53%), while Generations Y and X demonstrated progressively higher rates of moderate (39%) and high adherence (31.6%) (p < 0.05). Correlation analyses indicated that adherence to sustainable nutrition was positively associated with the application dimension of nutrition literacy, suggesting that both knowledge and practical skills may influence sustainable nutrition behaviors. Conclusion: Older and more educated participants achieved higher nutrition literacy and sustainable nutrition adherence scores. Knowledge alone is insufficient to ensure healthy or sustainable eating. Enhancing practical skills and providing sustainability-focused nutrition education may improve diet quality and public health.