Abstract
Malnutrition and environmental degradation remain pressing global challenges, However, the measurement of dietary diversity, which is crucial to understanding both nutritional adequacy and sustainability, remains debated. Using a mixed-scale approach, this work combines global datasets (FAO Food Balance Sheets, WHO Global Health Observatory, and World Bank indicators) with micro-level evidence from the Kenya Integrated Household Budget Survey (KIHBS) to investigate the following specific objectives: to analyse long-term global trends in animal-source calorie consumption and their sustainability implications, to examine global patterns in plant- and animal-based contributions to dietary diversity and their role in nutritional security across regions, to assess how different dietary diversity indices relate to health outcomes across income groups and to evaluate diet deprivation and sustainability among Kenyan households and identify key socioeconomic drivers. Multiple indices are compared, including the Simpson index, Shannon index, functional diversity, reference deprivation diet (ReDD) index, and human trophic level (HTL). The findings reveal that dietary diversity is a multidimensional construct with significant implications for both nutrition security and sustainability. While diversity is generally associated with improved nutritional outcomes, high diversity does not always equate to adequate nutrition, particularly when dominated by energy dense but nutrient-poor foods. The balance between plant- and animal-sourced foods has emerged as a key determinant of both health and environmental outcomes, with evidence indicating that both deficiency and excess can be detrimental. Moreover, current diversity metrics vary widely in their sensitivity to nutritional adequacy, environmental impact, and socioeconomic disparities. As such, composite, context-sensitive indicators are needed to more accurately capture the complexity of diet quality across different settings. The results underscore the need to shift from calorie-based assessments toward holistic frameworks that integrate nutritional value, ecological sustainability, and cultural relevance. In conclusion, this work provides a valuable perspective on the complexities of dietary diversity, offering a refined approach to measurement that can guide more effective policies and interventions. By emphasizing the importance of both nutritional adequacy and sustainability, it helps bridge gaps in current frameworks and contributes to the achievement of global health and sustainability goals, particularly those outlined in the SDGs.