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

Policies and programs often aim to improve the affordability of nutritious diets, but existing food price indexes are based on observed quantities which may not meet nutritional goals. To measure changes in the cost of reaching international standards of diet quality, we introduce a new Cost of Diet Diversity index based on consuming at least five different food groups as defined by the widely-used Minimum Dietary Diversity for Women (MDD-W) indicator, and compare those results with the cost of foods needed to meet an adult woman’s estimated average requirements of essential nutrients and dietary energy. Using national average monthly market price data for Ghana from 2009 through 2014, we find that the relative cost of reaching the MDD-W standard fluctuates seasonally and since mid-2010 has risen about 10 percent per year faster than inflation due to rising relative prices for fruit and fish, while the cost of nutrient adequacy rose even faster due primarily to increase cost of foods rich in vitamin A and calcium. Similar data for Tanzania from 2011 through 2015 show small increases in 2011 and 2012 but stable prices thereafter. Our methods can show where and when nutritious diets are increasingly (un)affordable, and which nutritional criteria account for the change. The specific foods included in each index depend on national price monitoring systems, but the method is generalizable to other contexts for monitoring, evaluation, and assessment of changing food environments.