Panel Data Evidence from Kenya

Kenya is one of the countries in SSA with the fastest supermarket growth rates during the last 20 years. Occurring mainly after 2002, Kenya became the country with the largest number of leading food retailers (a total of 10 in 2018) on the African continent [8]. While massive development is happening, Kenya currently suffers from a triple burden of malnutrition. While 26% of children aged under 5 years are stunted, more than 34% of female adults are overweight, and 27% of women suffer from anemia. Furthermore, about 6% of adults suffer from diabetes and over 26% from high blood pressure [20].

      The following findings are based on panel data that were collected in medium-sized towns in central Kenya in 2012 and 2015. While some of the towns already had a supermarket at the time of data collection, others did not have a supermarket yet. This provides a quasi-experimental set-up, which allows comparing diets, nutrition, and health outcomes between people with different access to supermarkets and other types of retailers.

      Supermarket Effects on Adults’ Diets and Nutrition

Table 1 summarizes findings by Demmler et al. [21] using the panel dataset on adults from Kenya (collected in 2012 and 2015) and panel regression models including fixed effects estimations (a form of statistical differencing), which allow for causal inference. The table depicts the effects of supermarket shopping on adults’ energy consumption from different food groups, the share of energy from highly processed foods, and the effects on nutritional outcomes. Supermarket shopping is measured in terms of a dummy variable that takes a value of 1 if any of the food consumed was purchased in a supermarket, and 0 if all foods were obtained from traditional sources. All estimates are net effects of supermarkets after controlling for confounding factors, such as income, age, education, and physical activity levels, among others.

Table 2. Effects of supermarket shopping on adults’ health

      While supermarket shopping significantly reduces the amount of daily energy from unprocessed staples (–112 kcal) and fresh fruits and vegetables (–124 kcal) consumed by adults, it increases the consumption of meat and fish (+24 kcal), dairy and eggs (+9 kcal), and vegetable oils (+60 kcal). Furthermore, supermarket shopping increases the share of energy from highly processed foods by 3 percentage points. Demmler et al. [21] clearly showed that supermarkets contribute to dietary changes towards more animal-source products and foods with higher energy density and higher processing levels. At the same time, supermarkets reduce the consumption of unprocessed foods and fresh fruits and vegetables.

Supermarkets also have significant effects on adults’ nutritional outcomes in Kenya. Demmler et al. [21] found robust evidence that shopping in supermarkets significantly increases adult BMI by 0.64 and significantly increases the likelihood of being overweight/obese by 7 percentage points (Table 1). While the effects on BMI estimated with the panel data are somewhat smaller than those estimated in earlier studies with cross-sectional data [14, 17, 22], they are more robust and reliable as they better control for possible endogeneity bias.

Fig. 1. Prevalence of child and adolescent stunting and underweight depending on household shopping behavior. *** Difference between children in households shopping and not shopping in supermarkets significant at the 1% level. Authors’ presentation based on data from Debela et al. [24].

      Supermarket Effects on Adults’ Health

      Table 2 shows the effects of supermarket shopping on adults’ fasting blood glucose (FBG), the likelihood of being pre-diabetic, and the likelihood of suffering from the metabolic syndrome. These results are based on cross-sectional health data collected in 2015 from the same adults in medium-sized towns in central Kenya. Demmler et al. [22] used instrumental variable models to control for endogeneity bias. The regression results suggest that supermarket shopping has a significant effect on all three health outcomes; it significantly increases the level of FBG by 0.3 mmol/L and increases the likelihood of suffering from pre-diabetes and the metabolic syndrome by 16 and 7 percentage points, respectively.

While Demmler et al. [22] found no significant effects of supermarket shopping on blood pressure or being hypertensive, the results showed a clear tendency that supermarket shopping does not only affect diets and the nutritional status of adults, but also health outcomes. While nutrition-related NCDs like diabetes and hypertension are mainly channeled through higher levels of BMI, Demmler et al. [22] also suggest that health outcomes might be directly affected through dietary changes. Since diets rich in bioactive compounds, micronutrients, and fiber are shown to be beneficial in order to prevent NCDs [23], a decrease in the consumption of fresh fruits and vegetables and unprocessed staples, as shown in Kenya [21], is likely to affect health outcomes directly.

      Supermarket Effects on Children and Adolescents

      While the effects of supermarket shopping on adult nutrition and health are negative and undesirable (higher rates of overweight/obesity and

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