Selenium deficiency is widespread and spatially dependent in Ethiopia

Adamu Belay^1,2

Dawd Gashu²

Edward J. M. Joy³

R. Murray Lark⁴

Dilnesaw Zerfu¹

E. Louise Ander⁵

Scott D. Young⁴

Liz Bailey⁴

Martin R. Broadley⁴

¹Food Science and Nutrition Research Directorate, Ethiopian Public Health Institute, Gulele Sub City, P.O.Box 1242 Addis Ababa, Ethiopia.
²Center for Food Science and Nutrition, Addis Ababa University, P. O. Box 1176, Addis Ababa, Ethiopia
³Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
⁴School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD, UK.
⁵Inorganic Geochemistry, Centre for Environmental Geochemistry, British Geological Survey, Nottingham, NG12 5GG, UK.

Introduction

Estimates of Micronutrient Nutrient Deficiencies at national and sub-national scales are inadequate across sub-Saharan Africa for reasons which include a lack of spatial information on food systems, reliable biomarkers of micronutrient status, and links between Micronutrient Deficiencies and health outcomes with multiple etiologies. This poses immense challenges for policy makers for prioritizing/targeting policy decisions, and for private sector investments. Selenium (Se) is an important micronutrient, which is essential in trace amounts in diets for optimal human and livestock health. In Ethiopia, there are no data which reflect the status of selenium at national and regional level.

Methods

The study design is multi-stage, cross-sectional survey including preschool and school-aged children, women and men. Participants (n=3297) were included for serum selenium analysis from the archived samples of the Ethiopian National Micronutrient Survey (ENMS) which covered nine regions and two city administrations between March 2015 and July 2016. The ENMS enumeration areas (EAs) or clusters are geographic areas defined by the Central Statistics Agency (CSA) for the Ethiopia Population and Housing Census (CSA 2008). In the ENMS, 366 EAs were randomly selected from all region or city administrations with probability of inclusion proportional to size. All preschool children (PSC, 6-59 months), 6 school aged children (SAC, 5-15 years), 3 men and 7 women of reproductive age (WRA) in 11 households per EA were selected for the actual survey. Socio-demographic information, geographic coordinate, anthropometry and blood were collected. A total of 4026 households in 366 clusters were selected; 92% (n=3700) of households in 353 clusters gave consent and were included in the study. Concentration of Se in serum samples was determined using ICPMS at the University of Nottingham under an MTA. Data were merged and analyzed using STATA; predictions of Se status were conducted using geospatial modelling in R.

Findings

Median serum Se concentration was 98.1 μg/L; 27.1% of a population had serum Se concentration less than an indicative threshold for deficiency (<70 μg/L). Age of participant was positively associated with selenium status (r=0.25, P<0.001). The median serum Se of Benishangul-Gumuz, Amhara and Oromia Regions were 56.3 µg/L, 66.9 µg/L and 77.4 µg/L, respectively. Altitude was positively associated with serum selenium status of the participants (r=0.312, P=0.018). Inflammation was negatively associated with selenium status. With presence of infection, the participants had 8.8 µg/L lower selenium concentration (95% CI:-15.37,-2.17) (P=0.009). Variation in serum Se status was observed across the country showing that Se status is under strong geospatial control. Using geostatistical methods it is possible to identify where individuals are likely to have serum Se concentrations below the thresholds for optimal activity of GPx3, an important antioxidant, and for the production of the thyroid hormone iodothyronine deiodinase. At ANH these results will be presented as maps.

Conclusion

The present study reveals that Se deficiency in Ethiopia is widespread, especially among PSC and SAC. Risk of Se deficiency is highly spatially dependent, which is likely to be due to environment-food system factors including soil type, landscape features, and food production and distribution. Serum Se concentrations were greater among populations living in the Rift Valley. These data suggest that the need to establish routine monitoring of Se status of the Ethiopian population in future surveys and investigate different strategies to enhance the intake of Se, including dietary diversity and agronomic biofortification, using multi-disciplinary and multi-sectoral approaches.

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