Toward a comprehensive definition of diet quality: perspectives from the Italian Society of Human Nutrition (SINU)

Aims Diet quality is a multidimensional concept linked to health outcomes, but its definition varies across studies and cultures. This perspective examines how diet quality is defined in scientific literature integrating evidence from dietary guidelines, diet quality indices, and recent research. Data synthesis Core principles consistently defining diet quality are adequacy, diversity, balance, and moderation. These translate into diets that meet nutrient requirements, include a variety of foods across food groups, ensure appropriate macronutrient distribution, and limit added sugars, salt, and unhealthy fats. Nutrient density and macronutrient quality further refine the concept, with emphasis on unsaturated fats and high-fiber carbohydrates. High-quality diets generally prioritize plant-based foods over animal products. Emerging dimensions extend diet quality beyond health to include environmental sustainability, degree of food processing, and socio-cultural factors such as cultural acceptability, affordability, and equitable access to food. Conclusions Diet quality is a holistic construct integrating nutritional health, sustainability, safety, and cultural relevance. It is not limited to a single dietary model, as multiple patterns can achieve high quality when these criteria are met, with the Mediterranean diet as a well-established example. Future evaluations should integrate nutritional, environmental, food security, food processing and cultural indicators.