Community and Public Health Nutrition
Market prices for nutrient-dense foods may influence adequacy of intake, but previous studies have focused on estimated average requirements (EARs) of a target group. The aim of this study was to measure sensitivity in the cost of nutrient adequacy (CoNA) to changing requirements over the life cycle from infancy through adolescence, pregnancy or lactation, and other potential influences such as phytates in food that limit absorption of zinc.
Using nutrient composition and monthly prices for 55 foods at 29 regional markets in Malawi over 10 years (2007- 2017), we computed the least-cost diets at each place and time that meet nutrient requirements for 23 age-sex groups. We applied four levels of nutrient requirements from dietary reference intake (DRI) data, using EARs and RDAs as well as upper limits (ULs) and acceptable macronutrient distribution ranges (AMDRs). We also considered the effect of phytate on the absorption of zinc in each food. All costs account for inflation using 2011 purchasing-power parity exchange rates (USD/day).
Results : The cost of nutrient adequacy shifts over the life cycle, peaking for males aged 14-18 (median CoNA of 1.39 with EARs and 1.72 with RDAs). For all groups, CoNA also varies across the distribution of nutrient requirements, for example, among females aged 19-30 the median CoNA is 1.00 to meet only EARs, rising to USD 1.16 to also stay within UL and AMDR limits and avoid risks from excess consumption. In Malawi, some foods have high phytate levels whose anti-nutrient effect on zinc absorption also raises costs, for example, median CoNA for a lactating woman aged 19-30 is 1.43 in our benchmark case with EARs, ULs and AMDRs, and USD 1.59 if phytate is considered, rising to 1.86 if EARs are replaced by RDAs.
We found high variation in the cost of meeting nutrient needs over the life cycle with large differences for males and females from infancy through pregnancy and lactation, as well as other influences on nutrient requirements for each group such as accounting for the effect of phytates on zinc absorption, and differences across the distribution of requirements from EARs to RDAs. Results will be useful for programs to target populations at risk of inadequate intake, and for research on the affordability of nutritious diets.
Funding Sources :
Bill & Melinda Gates Foundation (OPP1182628)