Metrics

The diet cost metrics used by the Food Prices for Nutrition team are the total diet cost per person per day, associated with three least-cost diets.

  •  “Healthy diet” – Cost of Healthy (Recommended) Diet (CoRD)
    • Minimum cost to meet a given set of food-based dietary guidelines, based on recommendations for food groups to meet nutrient needs, as well as proportionality and other goals.
  • “Nutrient adequate diet” – Cost of Nutrient Adequacy (CoNA)
    • Minimum cost to meet adequate calories but also adequate levels of all essential nutrients, namely carbohydrates, protein, fat, vitamins, and minerals, within the upper and lower bounds needed to prevent deficiencies and avoid toxicity.
  •  “Energy sufficient diet” – Cost of Calorie Adequacy (CoCA)
    • Minimum cost to meet energy requirements using the least expensive, available starchy staple food.

Least-cost diets represent the most affordable (cheapest, lowest cost) combination of foods that meet the criteria of these three diets. Our least-cost diets choose foods depending on the market and season, including seasonal and locally available foods that are subject to change depending on their availability and relative price.  

By definition, none of these diets reflect current consumption patterns. They are benchmarks against which to compare incomes and current food expenditure, which may be inadequate for nutrition and health and in any case would be chosen based on other criteria such as taste, preferences, and convenience.

The cost of a healthy diet is based on global average quantities of food groups recommended in national food-based dietary guidelines (FBDG). FBDG are developed to guide people to choose diets that meet nutrient needs and protect health, within culturally appropriate diet patterns. This is done through food group recommendations, with the logic that consuming a diversity of items within each food group in the amounts recommended will, on balance, roughly meet nutrient needs. (We find this to be true, with global results showing that least-cost diets meeting a variety of national FBDG meet 100% of macronutrient and about 94% of micronutrient needs on average.) Food group recommendations also meet other dietary needs beyond nutrient needs. Dietary risk factors are recognized as a top contributor to the global burden of disease globally, which have to do with the influence of non-nutrient dietary components of food (fiber, phytochemicals, influence on microbiome, food matrix, degree of processing, glycemic index, fatty acid profile/ratio) on health (including mental health), and the influence of proportionality between food groups. Furthermore, proportionality in food group intake ensures a culturally acceptable diet meeting at least a minimum standard for palatability and cultural norms, so the healthy diet is closer to actual food preferences, in terms of dietary pattern, than the energy sufficient or nutrient adequate diets.

FBDG simultaneously represent (1) a realistic way for regular people to select nutrient-adequate diets, as well as (2) diets that protect health against NCDs, as well as (3) diets that are dignified and culturally appropriate. Furthermore, in nations where FBDG have been elaborated, (4) FBDG are the official policy standard for what constitutes dietary needs. Without exception, each nation’s FBDG are intended for the general population – not as an aspiration or target only for a privileged few, but for all citizens. For this reason, many countries base social safety nets and nutrition education for low-income citizens on FBDG. For an indicator of economic access to nutritious food to meet dietary needs, the cost of a healthy diet is the appropriate standard.

For more information on the methodology, see: Herforth, A., Y. Bai, A. Venkat, K. Mahrt, A. Ebel, & W. A. Masters. Cost and affordability of healthy diets across and within countries: Background paper for the State of Food Security and Nutrition in the World 2020. FAO Agricultural Development Economics Technical Study, No. 9. Rome, Italy: Food & Agriculture Org., 2020.

For data and software tools for calculating the Cost of Nutrient Adequacy, see the Data & Code page of this website.

For more information on considerations related to the Cost of Nutrient Adequacy calculation, see also: Schneider, K. & A. Herforth, A. (2020). Software tools for practical application of human nutrient requirements in food-based social science research. Gates Open Research 4:179.


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