Measuring Global Dietary Diversity by Considering Nutritional Functional Dissimilarity and Dietary Guidelines.

Dietary diversity is essential for healthy diets and crucial for academic research and policymaking. However, existing measures often lack conceptual clarity, which limits their interpretability. This study proposes a new framework that classifies dietary diversity indices along two dimensions: whether they account for nutritional functional dissimilarity and whether they incorporate dietary guidelines. Based on this framework, four index types are defined. Using per capita consumption data for 14 food categories across countries from 1981 to 2022, eight indices were applied to assess global dietary diversity and its variation across 13 dietary patterns. The results show a general upward trend in global dietary diversity and dietary quality, with notable regional disparities influenced by dietary patterns, resources, culture, and socioeconomic factors. This study also finds non-linear links between dietary diversity, income, and urbanization, consistent with Bennett's Law and empirical evidence. These findings underscore the utility of the proposed indices in capturing complex dietary dynamics. This study recommends context-specific use of indices, policy attention in developing countries to maintain diversity during dietary transitions, and the development of more inclusive dietary guidelines that emphasize not only variety but also balance and nutritional function.