Research paper
Drewnowski A. Concept of a nutritious food: toward a nutrient density score. Am J Clin Nutr. 2005;82(4):721-732.
Why we cite it
Proposes the first systematic framework for quantifying nutrient density — the Naturally Nutrient Rich (NNR) score — which assigns objective nutrient density values to foods based on mean percentage daily values for 14 nutrients per 2000 kcal. This later evolved into the widely validated NRF9.3 index (9 nutrients to encourage minus 3 to limit, per 100 kcal). Relevant to the project’s argument that ultra-processed foods are nutrient-poor despite being calorie-rich: the NNR/NRF framework provides the quantitative basis for comparing whole foods against processed alternatives.