Subnational and lifecycle-specific estimates of diet costs support nutrition-sensitive policies and programmes

National level estimates of diet costs are increasingly being published and serve to track global goals and compare costs across countries. Subnational level estimates, which can be aggregated to a national average, can be used to inform local policies and programmes. This study has two objectives: First, to assess whether national level diet costs from the Fill the Nutrient Gap (FNG) analysis are in line with national estimates from the Food Prices for Nutrition (FPN) Project and discuss methodological differences. Second, to review the added value of subnational and lifecycle-specific estimates from FNG to inform design of policies and programmes for improving nutrition of the most vulnerable groups. We examined the subnational estimates and national level averages of the cost of energy-sufficient and nutrient-adequate diets calculated in 26 FNG country analyses. We assessed the correlation with the corresponding national-level estimates for 2017 that were published in the FPN DataHub for energy-sufficient (r = 0.79, p < 0.001) and nutrient-adequate diets (r = 0.61, p = 0.001). For many countries, subnational variation of diet costs within the country was as large as variation across countries. Of individuals considered in the FNG approach, the cost of a nutrient-adequate diet was found to be highest for the adolescent girl. Subnational and lifecycle-specific estimates of the cost of nutrient needs from FNG analyses provided valuable additional information that has successfully informed policies and programmes in health, education and social protection sectors. • The Fill the Nutrient Gap (FNG) analyzes subnational food environments for interventions to reach the most vulnerable. • Subnational variation in diet cost within a country can be as high as across countries. • FNG costs of nutrient adequacy are based on a composite of individuals across the lifecycle to reflect their vulnerability. • Adolescent girls face the highest cost of a nutrient-adequate diet across all FNG household members. • National cost estimates of nutrient adequacy from the FNG are broadly aligned with the Food Prices for Nutrition project.