Measuring the Affordability of Nutritious Diets in Africa: Price Indexes for Diet Diversity and the Cost of Nutrient Adequacy

Existing food price indexes are based on observed quantities that may not meet nutritional goals. To address this limitation, researchers have developed a new cost of diet diversity index based on the lowest-cost way to include at least five different food groups as defined by the Minimum Dietary Diversity for Women (MDD-W) indicator. The MDD-W indicator is a widely used measure of diet diversity that has been linked to nutrient adequacy in several low-income countries. The cost of diet diversity index is calculated by determining the lowest-cost way to meet the MDD-W criteria using national average monthly prices from agricultural market information systems or consumer price indexes. This approach allows researchers to track changes in the cost of nutritious diets over time and across different geographic locations. In Ghana, the cost of diet diversity index fluctuated seasonally and rose about 10% per year faster than national inflation since mid-2010, driven by rising relative prices for fruit. In Tanzania, there were much smaller changes in total daily costs, but more adjustment in the mix of food groups used for the least-cost diet. These findings suggest that the cost of nutritious diets is increasingly unaffordable in some African countries, particularly for vulnerable populations such as women and children. The researchers used two different data sources to calculate the cost of diet diversity index: an agricultural market information system in Ghana and the data used for national consumer price indexes in Tanzania. The results show that the cost of diet diversity index is a useful tool for monitoring changes in the affordability of nutritious diets over time and across different geographic locations. This approach can help policymakers and program managers identify areas where nutritious diets are increasingly unaffordable and develop targeted interventions to improve food security and reduce malnutrition.