Nutrition transition in urban Kenya: The role of supermarkets and nutritional knowledge

Nutrition transition is described as a shift in demographic and epidemiologic patterns; fostered through economic development, globalization, urbanization, and technological improvements. Depending on the stage of transition in a given society, changes in lifestyle and eating habits lead to an increased intake of processed foods, saturated and total fats, salt, sugar, and energy-dense beverages. Many developing countries are undergoing such a nutrition transition, which contributes to emerging problems in their health systems. For a long time, the elimination of undernutrition has been a top priority of development policies in low-income countries. Worldwide, it is estimated that 24% of all children under-five are currently stunted, mainly caused by sustained episodes of energy and micronutrient deficiencies. There has been remarkable progress in reducing this prevalence; still the number of stunted children continues to increase in African countries. While globally undernutrition and stunting are declining, overweight, obesity, and nutrition-related non-communicable diseases (NR-NCD) such as diabetes and hypertension are growing epidemically. The large majority of the worldwide NCD-related deaths occur in low- and middle-income countries. Especially for some African countries like Kenya, where stunting is still widespread and overweight and obesity are increasing rapidly, it is of immense importance to analyze and understand driving factors and prevent malnutrition in all its forms. Against this background, this dissertation presents three essays dealing with the ongoing nutrition transition and malnutrition in Kenya. In the first two essays, we investigate the influence of supermarket purchase on adult’s nutrition, diet, and health. In the third essay, we study the link between different types of maternal nutrition knowledge and child and adolescents’ nutritional outcomes. Kenya has experienced a rapid growth of supermarkets in recent years. Overall, the share of national grocery sales through supermarkets in Kenya is about 10%; with big cities already having a much higher share. At the same time, the country is struggling with many nutrition and health-related issues. While 35% of the children under-five are stunted, NR-NCDs are also a growing concern. More than 26% of all adults in Kenya are either overweight or obese. The national prevalence of diabetes and hypertension is estimated at 2.5% and 35%, respectively. The first two essays are motivated by the hypothesis that the rapid spread of supermarkets in developing countries contributes to the observed nutrition transition and thus causes changes in nutrition and health. Recent research revealed significant effects of supermarket purchase on dietary choices and the body mass index (BMI) in various developing countries. However to our knowledge the question whether supermarket purchase affects the prevalence of NR-NCDs has not been analyzed up till now. We add to the literature by using detailed health data and indicators of NR-NCDs. In addition, existing studies only had cross-sectional data available, so that possible bias due to unobserved heterogeneity remains an issue in the analysis of supermarket impacts. Here, we address this issue with panel data for dietary choices and BMI. Related to our third essay, maternal nutrition knowledge has been identified as one important factor to shape a healthy living environment for the whole household and to improve child nutrition. While associations between maternal nutrition knowledge and young children’s nutritional outcomes are well documented, it is much less understood, what type of maternal nutrition knowledge matters most and what are possible impacts on older children and adolescents. The first essay investigates the effects of supermarket purchase on BMI, as well as on health indicators such as fasting blood glucose (FBG), blood pressure (BP), and the metabolic syndrome. To this end, we use cross-section observational data from urban Kenya collected in 2015. Demographic, anthropometric, and bio-medical data were collected from 550 randomly selected adults. Supermarket purchase is defined as any food purchase done in supermarkets during the last 30 days. Instrumental variable (IV) regressions are applied to control for confounding factors and establish causality between supermarket purchase, BMI, and health. We find that supermarket purchase leads to higher BMI and an increased probability of being overweight or obese. Supermarket purchase is also related to significantly higher levels of FBG and a higher likelihood of suffering from pre-diabetes and the metabolic syndrome. Effects on BP cannot be observed. We conclude that supermarkets and their food sales strategies seem to have direct effects on people’s health. In addition to increasing overweight and obesity, supermarkets contribute to FBG, pre-diabetes, and the metabolic syndrome. In the second essay, we analyze robust effects of supermarket shopping on BMI and the probability of being overweight or obese. Further, we investigate the relationship of supermarket shopping on the share of energy from highly processed foods and the energy consumption of different food groups (unprocessed staples, fruits/vegetables, meats/fish, dairy/eggs and vegetable oils). For this analysis, we use panel data collected in 2012 and 2015. Econometric analysis is carried out with an unbalanced panel comprising 1,199 observations of male and female adults with differing supermarket access and use. Using fixed effects (FE) estimations, we find that supermarket shopping significantly increases adult’s BMI through changed diets. Supermarket shopping decreases the energy consumption from unprocessed staples, fresh fruits, and vegetables and increases energy consumption from dairy, vegetable oil, processed meat products, and highly processed foods. The data suggest that the BMI-increasing effect of supermarket shopping is primarily due to changed dietary composition, rather than higher total energy consumption. As ‘unhealthy’ foods are also available in traditional retail outlets, the contribution of supermarkets might be of an additional character driven by lager package sizes, pricing, advertising, and placing strategies. The third essay examines the link between maternal nutrition knowledge and long-term nutritional outcomes of children and adolescents between 5-18 years, focusing on whether associations differ depending on the type of maternal nutrition knowledge. We use panel data from urban Kenya collected in 2012 and 2015. After controlling for confounding factors, we find that maternal nutrition knowledge, measured in terms of an aggregated nutrition knowledge score, is positively associated with children’s height-for-age Z-score (HAZ). However, further disaggregation by type of maternal nutrition knowledge reveals important differences. The strongest positive association with child HAZ is found for maternal nutrition knowledge about the health consequences of not following recommended dietary practices. All three essays contribute to the existing literature about the links between transforming food systems and nutrition in developing countries. Concrete empirical research on such links is relatively scarce. Beyond nutrition, we also broadened the scope and analyzed effects of supermarket shopping on health and NR-NCDs. The results have immediate policy-relevance. Policy interventions should be designed such that positive effects of supermarket growth are strengthened, while negative nutrition and health impacts are avoided to the extent possible. One concrete idea could be to improve the offer and placement of fresh foods in supermarkets located in small urban centers. Furthermore, our results on the role of nutrition knowledge suggest that nutrition education should especially focus on raising awareness of the health risks associated with unsuitable dietary practices. As shown, awareness of such health risks among mothers and caretakers can help to improve long-term nutritional outcomes of children and adolescents.