Dietary species richness provides a comparable marker for better nutrition and health across contexts

Ecological diversity indices such as Hill numbers have been developed to estimate effective species numbers, yet the ability of Hill numbers to compare food biodiversity across contexts is unclear. Here we computed the between- and within-country variability of similarity-insensitive Hill numbers using dietary intake collected from prospective cohorts in nine European countries and cross-sectional studies in five low- and middle-income countries. We also assessed the relationships between more biodiverse diets, mortality rates and micronutrient adequacy. Only Hill₀, better known as dietary species richness (DSR), showed strong heterogeneity between countries and individuals within countries. Higher DSR was most strongly associated with lower mortality rates in Europe as compared to Hill₁, Hill₂ and Hill_∞, whereas relationships with micronutrient adequacy were comparable across Hill numbers in the global south. DSR can be used to assess progress towards more biodiverse diets, while also serving as a marker for the deleterious nutrition and health impacts associated with non-diverse diets.