Our results

Data visualization and download options for the cost and affordability of healthy diets:

RESEARCH & PUBLICATIONS

Featured examples

Cover of SOFI 2022
First page of Bai et al. 2021
Cover of Herforth et al. 2020

Primary sources

Applications using the cost of a recommended diet, by food group

Applications using least-cost items for nutrient adequacy

Data on food prices related to diet costs and affordability

LINKS TO PREVIOUS AND RELATED WORK

The diet cost and affordability metrics developed by the Food Prices for Nutrition project build on a long tradition of other work on food prices and nutrition, applied to global monitoring of food environments as called for by Herforth and Ahmed (2015) among others. We use nutritional requirements for a healthy diet to construct new kinds of food price indexes to monitor change and differences across and within countries, linking the cost of nutrient adequacy to costs by food group, first for Ghana and Tanzania in Masters et al. (2018) and globally by Herforth et al. (2020). Our central innovation is to automate the calculation of least-cost diets using locally available items at each time and place, converting data collected for other purposes into new kinds of price indexes to monitor food access for a healthy diet. This builds on and facilitates a wide range of other work, including the important precursors and ongoing complements to our project listed below.

Using least-cost diets to measure food access is a vibrant and growing area of research and practice, and we look forward to sharing ideas and learning from diverse investigators and practitioners working in this domain around the world. 

Previous and related work using the cost of nutrient adequacy to measure food environments

  • Since the initial formulation of least-cost diets for nutrient adequacy of Stigler (1945), many applications have used mathematical programming and modeled diets to address a variety of research and policy questions.
  • In nutrition, modern work focusing on the minimum cost per day of foods needed for nutrient adequacy was pioneered by Darmon et al. (2002) for adults in France, with applications to nutrition assistance ranging from the U.S. Thrifty Food Plan analyzed by Wilde and Llobrera (2009) to the Optifood approach to infant feeding in low-income settings led by Ferguson et al. (2008), and the related ‘Cost of the Diet‘ for households from Chastre et al. (2007) and Deptford et al. (2017). Large-scale global use of these techniques has been driven by de Pee et al. (2017) [link], in the ongoing Fill the Nutrient Gap work of the World Food Programme. Many others continue to use similar least-cost diet models in diverse settings, such as Conforti and D’Amicis (2020) for Italy.
  • In economics, the first modern use of least-cost nutrient adequate diets to track change in food systems over time was O’Brien-Place and Tomek (1983) for the United States, and the pioneering modern application to poverty measurement and social protection across countries globally is Allen (2017). At the same time, Omiat and Shively (2017) demonstrated the potential of least-cost nutrient adequate diets to track temporal and spatial variation using locally-available price data in Uganda, and Moatsos (2021) used similar methods to track long term historical trends in access to sufficient foods for nutrient adequacy in the world as a whole.

Previous and related work using the cost of a healthy (recommended) diet for food policy analysis

  • The formulation of food-based dietary guidelines allows use of least-cost items in each food group to track access to a healthy diet. Beyond our own project’s studies, Mekonnen et al. (2021) estimated the affordability of healthy diets in Nigeria, while Gupta et al. (2021) explore the cost of the EAT-Lancet diet in rural India. Parallel work at the World Bank was led by Dizon et al. (2019) for Bangadesh, Sri Lanka, Pakistan, and Afghanistan, and then Dizon et al. (2021) for Bangladesh, Bhutan, India and Nepal, as well as Dizon and Wang (2021) with additional detail for India.
  • The studies above focus costs per day, using quantities needed for health. An earlier approach focuses on relative prices per serving or unit of dietary energy, as done for the U.S. and Europe by Drewnowski and Darmon (2005) as well as Carlson and Frazão (2012) for the US, and Wiggins et al. (2015) for Brazil, China, Korea, Mexico and the UK, adding to early literature reviewed by Rao et al. (2013), expanded to all countries of the world for food groups by Headey and Alderman (2019) and for a single ‘basic plate’ of standard foods by WFP (2020) , with continued work on price changes by food group such Batis et al. (2022) in Mexico or de Mello et al. (2022) in Brazil.
  • To measure food environments more broadly, a closely related line of work aims to measure how retail prices among other factors affect obesity and other diseases, as pioneered by the INFORMAS network of Swinburn et al. (2013), including work on the price and affordability of healthy vs. unhealthy foods described by Lee et al. (2013) with ongoing applications in Africa led by Laar et al. (2022). Much of this research focuses on adherence to normative dietary guidelines and the cost of predefined food groups as in Gama et al. (2015) for children in Brazil, but some uses the cost of dietary patterns observed in healthier or less healthy people as in the work of Clark and Mendoza-Gutierrez et al. (2021) in Mexico.

How innovations brought by the Food Prices for Nutrition project complement and amplify other work

Methods for monitoring and analysis of diet costs developed by the Food Prices for Nutrition project complement and amplifies previous work in several ways:

  • First, we focus on methods for transformation of previously collected data. Our aim is to help national statistical organizations and international agencies use their existing price data collection and analysis systems to monitor food access for healthy diets on a routine basis, by combining data on:
    • availability and price of retail foods at local marketplaces, leveraging data collected by national statistical organizations to monitor inflation or by international agencies for early warning systems to guide intervention;
    • nutritional composition of each item from global and regional food composition tables, allowing analysts to transform prices for hundreds of differentiated items into cost per unit of each food group, accounting for edible fraction and water weight, as well as cost per unit of each nutrient;
    • dietary requirements for an active and healthy life, using national food-based dietary guidelines as well as upper and lower bounds for essential nutrients, and then automating the selecting of least-cost items needed for a healthy diet in each setting;
    • available income of households in each population, taking account of other basic needs and adjusting for the purchasing power of local currencies, generating a variety of affordability metrics for a variety of policy or program purposes.
  • Second, we aim for worldwide use, with both default standards and also customized solutions to address specific needs in particular settings, helping institutions develop monitoring systems adapted to their circumstances. This work is conducted in partnership with the World Bank and IFPRI and includes:
    • the global Healthy Diet Basket approach based on national dietary guidelines from all regions of the world, created in partnership with FAO and other UN agencies for monitoring food security and nutrition worldwide;
    • country studies using local dietary guidelines, created in partnership national statistical organizations and public health institutions, especially in our nine priority countries (Bangladesh, India, Pakistan, Burkina Faso, Ethiopia, Ghana, Malawi, Nigeria, and Tanzania);
    • developing new and improved approaches advancing the frontier of research, with students and collaborators around the world.
  • Finally, we support the improvements in food price data collection and reporting needed to monitor nutritional needs. This includes use of locally appropriate information on food composition and nutritional requirements, but in some cases also expansion of primary data collection to ensure coverage of:
    • item prices and availability in all food groups needed for a healthy diet — this is most important when using prices collected in market information and early warning systems that focus on farm commodities, whose food lists can be expanded to cover diverse vegetables, fruits, fish and other foods also available in local markets as demonstrated in early work with the WFP on the value of an expanded food list in Ghana;
    • prices and availability of low-cost items in popular markets used by people at risk of malnutrition — this is most important when using prices collected to monitor inflation, so their focus is national average spending which is dominated by higher-price items purchased by high-income people in urban markets, requiring expansion of data collection to marketplaces where lower-income people acquire their food, often in more remote locations as discussed in price differences by location in Malawi.
    • Visitors interested in seeing how these two countries currently monitor and report food price inflation can see Malawi’s National Statistical Office (NSO) reports here. For Ghana, visitors can track retail prices of individual foods from the Ministry of Food and Agriculture (MoFA) here, and see the Ghana Statistical Service (GSS) inflation monitoring here.  The worldwide posting of food prices is the subject of our recent paper on gaps and opportunities to monitor food systems for nutrition in Food Policy (2021).

Monitoring food access for healthy diets is a rapidly expanding field of work, involving close collaboration between a wide range of stakeholders. We look forward to hearing from you about opportunities to advance this urgent agenda for research and practice to meet global development goals.

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