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Sub-Saharan Africa is rapidly urbanizing. Urbanization has been discerned as a salient driver of the nutrition transition, a shift of dietary patterns away from traditional diets to diets high in sugar, salt and fat (Popkin, 1999; Ruel et al., 2017). While this has been well documented in the literature (e.g., Ameye, 2023; Cockx et al., 2018; Hawkes et al., 2017), two important facets are missing in this debate. First, it is still unclear whether and how urbanization affects individual dietary patterns within the household differently. Understanding intra-household allocation of resources is crucial to effectively target policies and programs. Second, it is not well understood what the underlying drivers of changing dietary patterns are. One important aspect may be the food environment, which modifies the effect of income on diets (Herforth & Ahmed, 2015). Where we stand in terms of food environment characteristics along the continuum of urbanization, and whether the changes in consumption run through this channel has not been systematically tested.
Our study aims to explore the association between urbanization, dietary habits and nutrient adequacy, considering aspects of the food environment as mediating channels. We follow three research objectives. First, we seek to understand how household nutrient consumption patterns, specifically the ratio of macro- to micronutrients, change along the rural-urban continuum. Second, we explore differential patterns within the household. And lastly, we gauge the extent to which this association is driven by changes in the food environment, i.e. unobserved preferences, food prices, physical access and food choice.
We leverage geocoded primary data, which we collected from October to December 2022 in Malawi. Our research design employs a three-stage random sampling approach along a rural-urban gradient to capture various types of food environments. We collected market-level information in conjunction with a household survey, assessing a total of 2300 individuals from 701 households and 89 different types of markets in the surrounding area of our sampled villages. In addition to basic household information, we conducted 7-day consumption expenditure recalls and collected information on shopping behaviors. For up to five members in the household we obtained 24-h dietary recalls and individual health, physical activity and anthropometrics. Our market survey included comprehensive information on physical aspects of markets and we captured information on food items and their retail price.
We utilize nighttime lights and population density as urbanization indicators. Nutrient consumption is derived from 7-day household consumption recall and 24-hour individual dietary recall using the Malawi Food Composition Tables (MAFOODS, 2019). Nutrient adequacy is assessed against dietary reference intakes (Schneider & Herforth, 2020). Household and individual data is linked with food environments using a spatial travel-time matrix (Weiss et al., 2020). Unobserved preferences are expressed as the difference between price paid by the household and retail price for a given food item. A market food prices index is calculated as the ratio of prices from nutritious non-staple foods to unhealthy foods of the most frequently consumed food items within each group from markets. Food choice is computed by the Euclidean distance between available and purchased items. We proceed with a regression analysis, using the overall macro- and micronutrient consumption ratio per adult equivalent as dependent variables for the overall household analysis and individual consumption levels for the within-household analysis. Our main independent variable is the urbanization indicator. In subsequent analysis we use food environment characteristics as mediators between the relationship from urbanization to dietary patterns. We control for socioeconomic factors, such as education, income, age and gender, and geographical and locality-specific characteristics. To ensure robustness, we instrument urbanization with a natural path IV (Damania et al., 2017).
Preliminary statistics show variations in household nutrient patterns across urbanization levels. Drawing from Ameye (2023), we anticipate a positive urbanization-diet relationship in Malawi. A major contribution of this paper is to disentangle whether the expected trend stems from entire households or specific demographics. It may be, for instance, that adults and specifically men are consuming more out-of-home meals, while females and children consume more nutrient-dense home-cooked foods. Yet, urban children may consume more snacks. The food environment is expected to play an important role in this relationship: more variety in the food environment is associated with lower food prices, which makes even for low-income households’ healthy diets more attainable. At the same time, urbanization is associated with an increased availability of unhealthy foods. These factors may be driving unobserved preferences and food choices, which we assume to be a strong driver of food consumption patterns. Many Sub-Saharan African countries undergo similar urbanizing processes and dietary changes. Understanding the variations and implications can help to inform policy and programmatic interventions that can help shape the food environment and improve nutrition outcomes.
References
Ameye, H. (2023). Dietary quality in rural areas, secondary towns, and cities: Insights from Tanzania. Food Security, 15(6), 1563-1584.
Cockx, L., Colen, L., & De Weerdt, J. (2018). From corn to popcorn? Urbanization and dietary change: Evidence from rural-urban migrants in Tanzania. World Development, 110, 140-159.
Damania, R., Berg, C., Russ, J., Federico Barra, A., Nash, J., \& Ali, R. (2017). Agricultural technology choice and transport. American Journal of Agricultural Economics, 99(1), 265-284.
Hawkes, C., Harris, J., Gillespie, S. (2017) Urbanization and the nutrition transition. In Global Food Policy Report, (4) pp. 34-41.
MAFOODS. (2019). Malawian Food Composition Table. 1st Edition. A. van Graan, J. Chetty, ... E. Marino-Costello (Eds). Lilongwe, Malawi.
Popkin, B. M. (1999). Urbanization, lifestyle changes and the nutrition transition. World development, 27(11), 1905-1916.
Ruel, M. T., Garrett, J., Yosef, S., \& Olivier, M. (2017). Urbanization, food security and nutrition. Nutrition and health in a developing world, 705-735.
Schneider, K. and Herforth, A. (2020). Software tools for practical application of human nutrient requirements in food-based social science research . Gates Open Res, 4:179
Weiss, D. J., Nelson, A., Vargas-Ruiz, C. A., Gligorić, K., ... Gething, P. W. (2020). Global maps of travel time to healthcare facilities. Nature Medicine, 26(12), 1835–1838.
