Linear growth failure of Ethiopian children : The role of protein, zinc and mycotoxin intake

Linear growth failure manifested as stunting is a major public health problem in developing countries. Stunting is often considered as an important marker of an adverse quality of population’s life and child development. Over 90% of stunted children live in 10 developing countries, in Asia and Africa. Ethiopia is the country with the high burden of linear growth failure. In 2016, it was estimated that about 5 million children suffered from poor linear growth or stunting in Ethiopia. The prevalence of stunting in Ethiopia has been reduced from 52% in 2000 to 37% in 2019, however, the number of stunted children has increased by about 1 million in the same period. There is a high level of commitment to reducing stunting globally and nationally. Although the government of Ethiopia formulated ambitious goals to reduce stunting, the progress to reduce stunting in Ethiopia remains too slow partly due to the fact that the aetiology of linear growth failure is still poorly understood. Stunting or poor linear growth is caused by a diverse and complex interaction of household, environmental, socioeconomic and cultural influences, related to, amongst others, poor nutrition, infectious diseases, unfavorable prenatal conditions and genetic disorders. The aim of this thesis was to contribute to the understanding of the aetiology of poor linear growth and stunting in rural Ethiopia by studying the effect of household-level quality protein maize (QPM) promotion and consumption, and the role of protein, zinc, and mycotoxins intake on linear growth of Ethiopian children. The first chapter provides background information on the role of QPM, protein, and zinc (in soil and serum) in linear growth of children. Furthermore, the research questions were described in detail.Chapter 2 describes a randomized controlled trial conducted in real practice in which households make their own decisions whether to adopt QPM, how much to adopt and cultivate, and whether and how to incorporate QPM into children’s diets. The intervention had two components: a) nutrition-focused adoption encouragement and provision of free QPM seed (AE), and b) a consumption encouragement (CE) primarily targeting female caregivers and encouraging earmarking and integration of QPM into diets for infants and young children. Eligible children (n=873) aged 6-35 months at baseline were randomly assigned to 3 groups: a first intervention group receiving AE only; a second intervention group receiving both AE and CE; and a control group. We hypothesized that promotion and consumption of QPM could improve the protein and amino acids status, which could, in turn, improve linear growth of children. Children consumed QPM based foods on average 4 days per week, while non-QPM based foods were consumed mostly. In addition, the quantitative intake of QPM was low (27 gram per day) contributing to only 5% of their total protein, 12% of lysine and 15% of tryptophan intakes, compared with conventional maize (80 gram per day) contributing to 16%, 9%, 13% of protein, lysine and tryptophan intakes respectively. Encouragement to adopt and feed QPM to infants and young children in a real-life setting had no effect on children’s protein biomarkers (p=0.19) or linear growth (p=0.17). Further evaluation of multi-year interventions is needed to understand how biofortified crops promoted at scale could change behavior and increase intakes at the household level which in turn improve biomarkers and outcomes in target populations.In chapter 3, we performed a cross-sectional analysis using baseline data of the QPM intervention study conducted in chapter 2. We investigated the association between protein intake, and protein and amino acids status with linear growth of children. The results indicated that protein intake (b=0.01, p=0.01) and protein status (b=2.58, p=0.04) as well as tryptophan intake/status (p<0.05) were positively associated with linear growth of children. Furthermore, most children had low energy intake (76%) coupled with high intestinal parasites (48%) and inflammation (35%). Also, protein and amino acids status were negatively correlated with inflammation, which suggests that the current requirement of protein and amino acids may not be adequate for children with low food intake or low energy intake and infection in Ethiopia. Linear growth failure in Ethiopian children is likely associated with low-quality protein intake and inadequate energy intake. Nutrition programs that emphasize improved protein quantity and quality and energy intake may enhance linear growth of young children.In chapter 4, we assessed exposure to aflatoxins and fumonisins measured in serum in two seasons, post-harvest and pre-harvest, and we also assessed mechanisms through which linear growth of children was affected. Children (n=873) 6-35 months old were enrolled in an intervention trial on quality protein maize consumption in rural Ethiopia as described in chapter 2. These children were stratified by baseline stunting status, and 102 children (50 stunted and 52 non-stunted) were randomly selected for this sub-study. Blood samples were collected during pre-harvest (August-September 2015) and post-harvest (February 2016) season. In the pre-harvest season, the proportions of children exposed to AFG1 (8%), AFG2 (33%) and AFM1 (7%) were higher than in the post-harvest season (4%, 28% and 4%, respectively). Likewise, the proportion of children exposed to any aflatoxin was higher in the pre-harvest than in the post-harvest season (51% vs. 41%). Exposure to fumonisins ranged from 0-11%, depending on the type of fumonisins. Exposure to any aflatoxin was not associated with inflammation (p>0.05), serum transthyretin (p >0.05) or serum IGF-1 (p >0.05), nor with linear growth (p >0.05) after adjusting for potential confounders. Our study revealed that exposure to most aflatoxins was high in pre-harvest season. Good practices in both post-harvest (to reduce accumulation of aflatoxins) and pre-harvest (to reduce aflatoxin levels) are needed for preventing contamination of aflatoxin. The mechanism in which aflatoxin affects linear growth of children is not clear. Aflatoxins are carcinogenic properties and the current exposure is a major public health problem that warrants intervention. Future studies on mechanisms between aflatoxin exposure and linear growth and sources of exposure with large sample size needed. In addition, future research is also needed on the complex and interacting pathophysiology of multiple mycotoxins and exposure management.In chapter 5, we use data from the cross-sectional, nationally representative Ethiopian National Micronutrient Survey (n=1776), which provided anthropometric and serum zinc (n=1171) data on children aged 6–59 months. Data on soil zinc levels were extracted for each child from the Africa Soil Information Service. With these data, we assessed the geographic distribution of poor soil zinc, poor zinc status and growth faltering at the national level. Zinc deficiency in soil was prevalent (20%) at the national level, with a higher prevalence in low land of Ethiopia (87%). Nationally, one in four children was zinc deficient, as measured by serum zinc level. High zinc in agricultural soils was positively associated with zinc status (b=0.9, p=0.02), however, linear growth of children was not associated with soil zinc or serum zinc. The findings from our study suggest that agricultural biofortification of zinc could be an alternative strategy for reducing zinc deficiency in developing countries. In Ethiopia most households consume food that comes from own production, however, crop production on zinc-deficient soils and its effect on human health has not yet been studied. Therefore, a future longitudinal experimental study on the effects of soil zinc application on crop zinc content and human serum zinc levels will help to elucidate this relationship. The phytate content of foods may affect zinc bioavailability. Future research is also needed on the effect of phytate on zinc bioavailability of crops grown on zinc-deficient soils.Finally, chapter 6 discusses the main findings, and the internal and external validity of the studies addressed in this thesis. Furthermore, the public health perspective including recommendations for possible future research is presented. Overall, we can conclude that low protein (of low quality) intake, high prevalence of zinc deficiency and high exposure to multiple aflatoxins are public health problems in Ethiopia. Linear growth of children is positively associated with protein intake, energy intake, as well as protein status, but not with zinc soil levels, zinc status or multiple aflatoxin exposure. Our study has demonstrated that the implementation of QPM in real life had no effect on the protein and amino acids status nor on linear growth of children. Therefore, in our study and also in other nutrition intervention programs, measuring intermediate indicators as outcomes of improved linear growth may be a more feasible approach than measuring linear growth or stunting.