Selenium deficiency risks in sub-Saharan African food systems and their geospatial linkages

Abstract

Selenium (Se) is an essential element for human health. However, our knowledge of the prevalence of Se deficiency is less than for other micronutrients of public health concern such as iodine, iron and zinc, especially in sub-Saharan Africa (SSA). Studies of food systems in SSA, in particular in Malawi, have revealed that human Se deficiency risks are widespread and influenced strongly by geography. Direct evidence of Se deficiency risks includes nationally representative data of Se concentrations in blood plasma and urine as population biomarkers of Se status. Long-range geospatial variation in Se deficiency risks has been linked to soil characteristics and their effects on the Se concentration of food crops. Selenium deficiency risks are also linked to socio-economic status including access to animal source foods. This review highlights the need for geospatially-resolved data on the movement of Se and other micronutrients in food systems which span agriculture–nutrition–health disciplinary domains (defined as a GeoNutrition approach). Given that similar drivers of deficiency risks for Se, and other micronutrients, are likely to occur in other countries in SSA and elsewhere, micronutrient surveillance programmes should be designed accordingly.

Increasing zinc concentration in maize grown under contrasting soil types in Malawi through agronomic biofortification: Trial protocol for a field experiment to detect small effect sizes

“…A nested analysis of variance for the data on grain Zn concentration in the pilot trial provided an estimate of the variance components for the random variation around treatment responses for the between‐plot within‐block effects, and the between‐block within site effects. With just three sites, we did not examine the between‐site variance component, but we approximated this from the correlated variance component of the variogram for grain Zn concentration from a national survey of maize grain carried out in Malawi as part of the GeoNutrition project (Gashu et al., 2020; Ligowe, Phiri, et al., 2020). This variance will be somewhat inflated by effects of variation between soil types at national scale, so it is conservative to treat it as an estimate of the between‐site variance component in our proposed experiment.…”

Selenium Deficiency Is Widespread and Spatially Dependent in Ethiopia

“…However, the distribution of deficiency risks is highly variable, which poses challenges for policy makers for targeting appropriate interventions. There are few data on population Se status globally, especially in sub-Saharan Africa [6,7]. The prevalence of Se deficiency on national scales in Africa was estimated indirectly, based on Se supplies in food systems, revealing that approximately 22% of the population of Africa is at risk of Se deficiency, with the prevalence of deficiency exceeding 60% in eight countries in sub-Saharan Africa [6].…”

Spatial prediction of the concentration of selenium (Se) in grain across part of Amhara Region, Ethiopia

“…They hypothesized that Se deficiency risks were linked to soil and/or landscape features ( Gashu et al, 2016a ). Reliable data on the Se status of soils and crops in Ethiopia, and elsewhere in SSA, are lacking ( Ligowe et al, 2020 ). Sillanpää and Jansson (1992) reported the Se status of 126 soils and co-located plants (wheat or maize) in Ethiopia.…”

“…Sillanpää and Jansson (1992) concluded that the Se status of crops in Ethiopia was generally satisfactory but that localized deficiency may exist. Ligowe et al (2020) re-analysed these data. Topsoil Se concentration, following acid ammonium acetate-EDTA universal extraction, ranged from <5–32 μg L −1 , and there was no evidence for relationships between concentrations of Se in soil and concentrations in maize or wheat.…”