Frequently Asked Questions

KEY CONCEPTS

A healthy diet meets nutritional standards set by dietary guidelines, with sufficient diversity and quantity within and between food groups to achieve nutrient adequacy and protect against diet-related diseases.

There are many definitions of a “healthy” diet pattern at national, regional and global levels. In this case, we select the national food-based dietary guidelines (FBDGs) of several countries from diverse regions, in order to represent a range of dietary recommendations which have been articulated by UN Member States. Dietary patterns have been studied extensively in the nutrition epidemiology literature, relating specific foods and proportionality of different food groups to disease incidence and prevention.

A diet that meets calorie needs alone may be sufficient for short-term survival, but not long-term health or well-being. It does not meet the definition of food security: adequate food to meet dietary needs and food preferences for an active and healthy life. A nutrient adequate diet meets calorie and nutrient needs (defined by a specific standard for specific populations) but does not necessarily meet dietary guidelines (proportionality between food groups), and does not necessarily satisfy food preferences. Healthy diets are protective of long-term health, and FBDGs are also designed to meet general cultural food preferences. Thus, ensuring access to healthy diets meets the full UN definition of food security.

Source: Herforth et al. 2020

Most marketplaces offer a variety of items to meet other needs, such as taste and convenience, which consumers with higher incomes can afford to buy.  Our aim is to measure the lowest cost at which a country’s food systems deliver the calories and essential nutrients and food groups required for each dietary standard, so as to identify the income level required to afford that level of diet quality. Least-cost diets allow for substitution among locally available items, based on the most affordable combination of foods that meets each definition of diet quality. 

Source: Herforth et al. 2020

National food-based dietary guidelines (FBDGs) provide context-specific advice and principles on healthy diets and lifestyles, which are rooted on sound evidence, and respond to a country’s public health and nutrition priorities, food production and consumption patterns, sociocultural influences, food composition data, and accessibility, among other factors.

Typically, FBGDs propose a set of recommendations in terms of foods, food groups and dietary patterns to provide the required nutrients to promote overall health and prevent chronic diseases. Yet, many countries are now moving towards more holistic perspectives by addressing food combinations (meals), eating modalities, food safety considerations, lifestyle and sustainability aspects in their FBDGs.

Source: FAO

COST OF A HEALTHY DIET INDICATOR

To calculate this metric, you will need *retail* food price data from markets with an adequate number of food items and food groups. It is important to consider geographic distribution, frequency of data collection (across seasons, etc) and data quality. You will also need to select a diet quality standard: either a national quantified set of food-based dietary guidelines, or the global Healthy Diet Basket.

You can use our Technical Assistance Tools to prepare your dataset and run the calculation with your preferred software.

The Cost of a Healthy Diet is computed using the least expensive foods available in each category at each place and time. Total cost per day can be disaggregated by food group, showing cost per day of the least expensive locally available items in each food group.

Source: Herforth et al. 2020

There are strengths and limitations to different food price data sources. When calculating Cost of a Healthy Diet, it is important to start with an adequate number of food items, and consider geographic distribution, frequency of data collection and overall data quality. 

One of the most reliable sources of food price data is official government data that is used for measuring inflation (via the Consumer Price Index) — typically this is monthly data collected by your National Statistics Office / Bureau, as well as that of Ministries monitoring food prices for their policies & programs. CPI data is collected in a standardized way (i.e. for the same list of items, at the same time each month) – enabling easy comparison – and often includes a diverse range of culturally-relevant foods for the country in question. 

Additional data source is Household Consumption and Expenditure Surveys (HCES), which report expenditure shares on food, food groups and food items – and provide expenditure shares for different segments of the population. HCES data is representative at sub-national level, but the survey(s) are typically carried out once every few years – and is not a suitable data source for routine monitoring. 

Lastly, the World Bank’s International Comparison Program (ICP) provides a high-quality, globally comparable dataset for 2005, 2011 and 2017 – including 208 global foods & beverage items, with additional region-specific lists. However, items are limited to comparable products sold across multiple countries – meaning that some low-cost items unique to a give country may be missing. Additionally, the ICP reports a national, annual average price for each item which makes it difficult to consider seasonal or sub-national variation. 

The Cost of a Healthy Diet indicator is calculated as the daily cost for an adult individual, in a specific time and place. We do not currently carry out analysis the household level, given the wide range of nutrient and caloric needs across age groups – especially infants, young children and adolescents. 

Nutrients alone do not explain the relationship of food to health, as there are many non-nutrient components of food, including but not limited to fibre, phytochemicals, the food matrix, and interactions between these. FBDGs focus on foods rather than nutrients, and typically concentrate on proportionality of food group intake. 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.

Source: Herforth et al. (2020)

It will be published in the UN State of Food Security and Nutrition in the World report (SOFI 2022), launching July 6 2022. On July 14, 2022, we will be launching the interactive the Food Prices for Nutrition DataHub – please join us!

USE IN POLICY & PLANNING

In all, we estimate that 3 billion people globally lack sufficient income to purchase the least-cost form of healthy diets recommended by national governments. The majority of these reside in Southern Asia (1.3 billion) and sub-Saharan Africa (829 million), with high numbers also in South-eastern Asia (326 million) and Eastern Asia (230 million). 

Source: Herforth et al. (2020)

While cost is a common consideration for consumers – other influences on food choice may include culinary practices, taste and convenience, or the time required to prepare each meal.

A variety of policy levers are needed to improve access to healthy diets. Our results show that the cost of either nutrient-adequate or healthy diets in the market is more than many people can afford; we do not account for food access via cultivation or wild harvesting. For people and places with sufficient local resources, production and harvesting of vegetables, legumes, fruits, dairy and eggs, fish and other foods can be important to provide access to nutrient adequate and healthy diets where the market does not. Agriculture and rural development should prioritize cost reductions for vegetables and fruits, and protein-rich foods including dairy. More broadly, reducing the year-round cost of acquiring sufficient quantities to meet dietary needs will require big changes in production and distribution. The public and private actions needed to lower costs will vary by location and type of food. Access to supplies from diverse sources within and between countries is also important to overcome local resource constraints and gain resilience to shocks at any one place. Finally, actions to improve storage and trade, combined with actions to improve production and distribution, can sustain a rapid shift in agriculture and food systems that bring healthy diets within reach.

Source: Herforth et al. (2020)

Other initiatives researching diet cost (such as “Cost of the Diet” and WFP’s Fill the Nutrient Gap) have focused on the cost of nutrient needs. The Cost of a Healthy Diet indicator, developed by Food Prices for Nutrition, extends beyond nutrients to look at healthy diet patterns and adherence to dietary guidelines – such as national Food Based Dietary Guidelines (FBDGs) – which are designed to meet nutrient needs in behaviorally realistic ways. 

Unlike other indicators, Cost of a Healthy Diet does not rely on linear programming – making it relatively easy to compute. With a commitment to monitoring, we seek to leverage the abundance of data already collected in existing national and international monitoring systems. Our work also support countries to run the calculation(s) in their own data systems, and provides technical assistance  for them to carry out routine analysis over the long term.

The Cost of a Healthy Diet is regularly monitored by the FAO and shared in the annual State of Food Security and Nutrition in the World, which reports the indicator at country, region and global levels. We actively collaborate with WFP to incorporate Cost of a Healthy Diet in their ongoing work in countries, and welcome collaboration with other initiatives & organizations to support calculation of this indicator. 

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