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.