Household consumption, individual requirements, and the affordability of nutrient-adequate diets - An application to Malawi
Schneider, Kate.
2021
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Thesis (Ph.D.)--Tufts
University, 2021.
Submitted to the Dept. of Food and Nutrition Policy and Programs.
Advisor: William Masters.
Committee: Patrick Webb, and Luc Christiaensen.
Keywords: Agriculture economics, Nutrition, and Public policy.
This thesis develops the first extension of least-cost diet calculations from individuals to whole households ... read more of differing compositions. Assessing whether individuals can and do meet their nutrient needs is empirically challenging. This thesis is among the first to comprehensively tackle these issues by assessing the affordability of nutrient-adequate diets in a low-income country setting, in this case Malawi. To do so, it expands the literature by first establishing aggregate nutrient requirements at the household level by defining the level of diet quality needed when meals are shared within the household, as they are in Malawi and many other settings. The resulting (normative) diet is denser in nutrients than any one member would need on her own, but sufficient to satisfy the nutrient needs of the neediest member consuming sufficient energy from the shared meal. Second, it applies linear programming models to calculate least-cost diets that meet a) individual requirements, and b) this shared household level of diet quality across space and time, as well as according to specific household composition. Importantly, least-cost diets allow for substitution over food items to meet nutrient needs using locally available foods at prevailing prices. Finally, it explores the effectiveness of different policy options to increase the affordability of nutrient-adequate diets. In assessing the affordability of nutrient-adequate diets in low-income settings this thesis provides the first application of aggregate household nutrient requirements based on their observed demographic composition and the nutrient density needs of all members. Extending least-cost diet calculations from individuals to whole households makes a pertinent methodological contribution in settings where households share meals as prior applications have not considered the diet quality needed by meals that are shared by members with differing nutrient needs, and what that diet costs. Data from a household panel of nationally representative consumption surveys in 2010, 2013, and 2016/17 are first merged with local food composition tables and individual nutrient requirements. Household demographic composition and food consumption are used to calculate household nutrient requirements and intakes. Next, household data are matched with monthly retail prices of the foods available at 25 markets from January 2013 through July 2017. We develop a bounded approach to estimate cost under current conditions comparing a lower bound that is sufficient only if foods and nutrients are targeted to individuals (individualized), and an upper bound that incorporates family food sharing and ensures the needs of the neediest member are met (shared). We then run more than 1.5 million linear models for every household in each month during this period to calculate the lowest cost diet meeting nutrient requirements at each bound and under eight policy scenarios. We compare diet costs to household incomes in 2013 and 2016/17 to assess affordability and assess seasonality over the full time period. Using the shadow cost of individual nutrients, we identify the costliest nutrients to obtain and those that impede the availability of a nutrient-adequate diet. Finally, we model changes to the shared cost under eight policy scenarios. Our findings suggest that poor quality diets in Malawi are largely a function of inadequate availability and access to nutrient-dense foods, and partly a reflection of Malawi's soil conditions. We find that local diets as currently consumed are not optimal in terms of nutrient density relative to aggregate household requirements. These diets are insufficiently dense in selenium, vitamin B12, lipids, riboflavin, phosphorus, and zinc and too dense in carbohydrates, iron, and copper. Differences by urban/rural location or household wealth are minimal, suggesting too few nutrient dense foods are available or accessible to most people. For rural families, adequate shared diets were available only 60% of the time from 2013-2017; meaning that for 40% of the time available foods cannot be combined at any cost to provide a level of diet quality that allows for optimal sharing to meet all needs. We find the individualized diets exhibit a degree of seasonal fluctuation comparable to that seen in food groups while the shared diet varies greatly from month-to-month. At a median cost of $2.26/person/day (2011 US$ PPP), the shared diet is unavailable or unaffordable to 80% of rural Malawian households within their current food spending and for 69.5% even if spending all their resources on food. The individualized diet is more available - 90% of the time on average - at a lower cost ($1.79/person/day), but still unavailable or unaffordable for 62% of the rural population within current food budgets and for 44% even if spending all resources on food. With respect to the drivers of diet availability and cost, we find that as households grow the cost to acquire 1,000 calories of a sufficiently nutrient dense diet increases, reflecting the need for more nutrient dense diets when women and children are present. Shadow prices show that riboflavin is the costliest nutrient in the food system while policy simulations reveal that selenium is the nutrient hindering the availability of nutrient-adequate diets. Overall, this thesis offers several metrics of food system performance with respect to nutrition including a nutrient density measure of household diet quality relative to shared needs, the cost of a nutrient-adequate diet for whole households bounded by two sharing rules optimizing resources at the lower bound and eating together in accordance with cultural norms at the upper bound, and the cost of individual nutrients in the market. The methodological contribution exhibits the level of detailed, granular analysis that is possible when household survey and food price data are both available and can be merged. It has demonstrated that Malawi's food system does not currently facilitate access to sufficient nutrients for whole households. In the short term, our simulations revealed biofortification of maize with selenium to be the most promising intervention, which would result in nearly universally available shared diets at half the daily cost. In the long term, more nutrient-dense foods - particularly conferring selenium, riboflavin, B12, and zinc - at more affordable prices, are necessary to facilitate access to nutrient-adequate diets for all.read less - ID:
- 3b591p96p
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