Are Healthy Foods Affordable? The Past, Present, and Future of Measuring Food Access Using Least-Cost Diets

This review describes the history, current practice, and prospects for measuring a population's access to foods for health using the lowest-cost locally available items, in contrast to quantities actually chosen, so as to distinguish between unaffordability of healthy diets and other causes of malnutrition. Retail prices, cost per day, and affordability relative to earnings have been used to measure food access for centuries, driving early definitions of poverty and income thresholds for subsistence. Substitution between items based on food composition was introduced soon after nutrient requirements were quantified, leading to the development of linear programming and other diet modeling techniques. This article describes how and why modern diet cost and affordability metrics have been adopted by international organizations, government agencies, and researchers to monitor food markets and guide intervention, concluding with new frontiers for research on other factors limiting access to healthy diets, such as cooking costs and time use, and factors that cause displacement of low-cost healthy diets by other foods.