Dietary diversity and health outcomes across country income groups: evidence from globally available data

Dietary diversity is widely recognized as a key element of food and nutrition security. However, its influence on health outcomes in different national development stages remains underexplored. We use FAOSTAT Food Balance Sheet data on national per-capita food availability, WHO health indicators such as prevalence of undernutrition, obesity, diabetes, life expectancy, and World Bank income group categories from 2011 to 2022, and panel and cross-sectional regression models to study how diet diversity, measured with the Simpson, Shannon, and Count indices, impacts health. The findings reveal complex and context-dependent relationships. In low-income countries, increased dietary diversity is associated with decreased life expectancy and an increased prevalence of obesity and diabetes. In lower-middle-income countries, increased diversity significantly is related to the prevalence of underweight and is positively associated with life expectancy. Upper-middle-income countries show mixed results, with diversity linked to both health indicators and rising obesity rates, highlighting a transitional dietary shift. In high-income countries, dietary diversity is correlated with improved health outcomes, including a lower prevalence of obesity and diabetes. Additionally, we examined the relationship between dietary diversity and plant-based calorie intake shares and found that plant-dominated diets do not consistently improve diversity or nutritional adequacy, particularly in lower-income settings. These findings emphasise the need for context-specific dietary guidelines and a policy shift from focusing on ‘green’ diets to prioritising actual nutritional quality. Methodologically, future studies should consider (nutrient-) ‘rich diet diversity’ measures, giving more weight to nutritious food items than to empty calorie providers.