Nutrition, health and microbial ecology of traditional fermented foods in Zambia

Abstract

The widespread societal, development and health problem of undernutrition in many developing countries motivated my research described in this thesis. Despite past interventions and economic developments, many developing countries still face high levels of undernutrition; especially stunting (linear growth failure), deficiencies in zinc, vitamins A and B12, and folate, mainly in children under the age of five years. Some of the current and proposed interventions to improve nutritional status include dietary diversification, sugar fortification with vitamin A, high dose vitamin A capsule distribution to under five children twice every year, maize meal fortification, and others. Dietary diversification and improvement in the food preparation methods such as fermentation are potential means with potential to improve availability of nutrients especially for vulnerable populations. For this thesis, the focus is on Zambia, which is one of the most undernourished countries in the world, with 48% of the population considered undernourished. As Zambia is dependent on mainly maize as a staple food with lower consumption of animal food sources, diversification of diets presents an opportunity to combat undernutrition in this population. Within this, the traditional use of fermented foods presents an opportunity for improvement in nutrient intake in the population especially of children below the age of five years. My thesis explores this potential. My research has three central aims. (1) Elucidating the nutritional potential of the traditional fermented foods Mabisi and Munkoyo to complement the diet of vulnerable groups such as children under five years old (Chapter 2). (2) Determining the nutritional aspects and microbial composition of the target traditional fermented beverages Mabisi and Munkoyo and whether microbes influence the level of nutrients in the two products (Chapter 3). (3) Understanding the influence of the favourable bacteria in the products in shaping human gut microbiota towards more favourable composition and its impact on nutritional status (Chapters 4 and 5). In Chapter 2 I describe the potential contribution of Mabisi and Munkoyo to nutrient intake in children under the age of five years using Optifood, a linear programming software that was developed by WHO and partners. Secondary dietary intake data collected using 24-hour recall method was modeled to develop food based recommendations (FBRs), for children aged 1-3 and 4-5 years in Mkushi district of Zambia. Three scenarios per age group were modeled to determine weekly food-based recommendations based on: (1) food based recommendations with the local available foods, (2) food based recommendations with inclusion of Mabisi, a fermented milk beverage, and (3) food based recommendations with inclusion of Munkoyo, a cereal fermented beverage. The scenarios were compared to assess whether food based recommendations with the addition of Mabisi and/or Munkoyo achieved better nutrient intake. FBRs based on only locally available non-fermented foods did not meet ≥70% of recommended nutrient intake (RNI) for calcium, fat, iron and zinc. The addition of Munkoyo to the FBRs did not reduce the number of problem nutrients, but after adding Mabisi to the FBR’s only iron (67% of RNI) remained a problem nutrient in the 1-3 year age group and only zinc (67% of RNI) remained a problem nutrient in the 4-5 year age group. Mabisi, a fermented milk product in combination with the local food pattern is a good additional source of nutrients for these age groups. However, additional nutrition sensitive and cost-effective measures would still be needed to improve nutrient intake, especially that of iron and zinc. Chapter 3 describes the results obtained from laboratory analysis of Mabisi and Munkoyo samples collected during a cross sectional study in Mkushi to determine their nutritional composition and microbial communities. It was hypothesized that Mabisi and Munkoyo each contain distinct microbial communities and that nutritional composition depends on microbial composition. With respect to the variation in microbial community structure, I therefore addressed whether the use of different raw materials can explain the variation in the structure of microbial communities, and if variation in nutritional composition can be explained by differences in microbial community structure. Here, we characterized the nutritional composition and microbial community composition of Mabisi and Munkoyo. We found that the two products are different with respect to the nutritional and the microbial composition. Mabisi was found to have higher crude protein, fat, and carbohydrates than Munkoyo. The microbial community composition was also different for the two products, while both are dominated by lactic acid bacteria. Our analyses showed that variation in nutritional composition, defined as how much consumption would contribute to estimated average requirement (EAR), might be explained by variation in microbial community composition. Consumption of Mabisi appeared to contribute more to the estimated average requirement (% of EAR) and its inclusion in food based recommendations is warranted. We further found evidence that through fermentation of the raw materials (raw milk for Mabisi and cereal for Munkoyo), the levels of B-vitamins can increase. Levels of increase likely depend on the exact composition of the microbial community used for fermentation. Our results show the potential of Mabisi to add value to current diets and suggests that variations in microbial composition between specific product samples can result in variations in nutritional composition. The in vitro experiment in Chapter 4 of this thesis assesses the impact of Mabisi and Munkoyo on the gut microbiota focusing on the potential changes in metabolite profiles of gut microbiota taken from stool samples upon exposure to Mabisi and Munkoyo. The shifts in metabolite profiles were correlated to changes in abundance of a key indicator bacterium (Lactobacillus) for healthy gut microbiota composition. We exposed stool samples to these products and various controls and measured concentrations of short chain fatty acids (SCFAs) and used these as an indicator of beneficial bacteria activity and measured shifts in levels of the indicator beneficial bacterium Lactobacillus. Results show that exposure of the gut microbiota from stool to Mabisi and Munkoyo results in higher levels of SCFAs and also higher levels of Lactobacillus. These results support the idea that consumption of fermented foods can result in healthier metabolism of the gut microbiota as measured with SCFA concentrations. These results can inform further more complex in-vitro as well as in vivo studies on the effects of the traditional fermented foods on gut microbiota metabolism and composition. Chapter 5 describes a survey that was undertaken in Namwala and Mkushi to determine the effect of consuming traditional fermented foods on gut microbiota composition and nutritional status in children 6-24 months old in rural Zambia. Data on food consumption, morbidity and socio-demographic together with stool samples were collected from children aged 6-24 months residing in Namwala and Mkushi in Zambia. The stool samples were analysed for the composition of gut microbiota and for concentrations of short chain fatty acids (SCFAs) as a proxy for microbial metabolism. This data was then linked to data on intake of traditional fermented foods using multivariate analysis of variance. Gut microbiota of children who are fermented beverages consumers was associated with higher relative abundance of Bacteroides and Lactobacillus than the non-consumers. Higher levels of these bacterial groups have been associated with benefits to the host. There was no difference for the SCFA concentrations between the fermented foods consumers and non-consumers, which may be because other parts of the diets that we did not control for also contribute to SCFA production. The results imply that consumption of the two traditional fermented foods used in this study promotes a healthier gut microbiota composition in the children in Zambia. Our results warrant future more formal tests such as controlled human feeding trials to further validate our findings. In the framework of the work in this Thesis it is evident the two products are good sources of nutrients and have potential probiotic effects to confer better health and nutritional status to its consumers. The goal of contributing to improvement of people’s lives through dietary intake improvements using traditional fermented foods could be achieved as shown in this thesis. The work highlights the need to explore locally available and culturally accepted foods, more so the fermented foods such as Mabisi and Munkoyo in the fight against undernutrition. However further work to generate more evidence for the formalization of our products Mabisi and Munkoyo with key messages on benefits formulated for dissemination to the current and potential consumers.