The risk of selenium deficiency in Malawi is large and varies over multiple spatial scales

Felix P Phiri,Edward J M Joy,Andrew Salter,Michael J Watts,Jellita Gondwe,Parminder S Suchdev,Martin R Broadley,Allan D C Chilimba,John C Phuka,Elizabeth H Bailey,Diriba B Kumssa,E Louise Ander,R Murray Lark,Scott D Young,Benson Chilima,Alexander A Kalimbira

doi:10.1038/s41598-019-43013-z

Abstract

Selenium (Se) is an essential human micronutrient. Deficiency of Se decreases the activity of selenoproteins and can compromise immune and thyroid function and cognitive development, and increase risks from non-communicable diseases. The prevalence of Se deficiency is unknown in many countries, especially in sub-Saharan Africa (SSA). Here we report that the risk of Se deficiency in Malawi is large among a nationally representative population of 2,761 people. For example, 62.5% and 29.6% of women of reproductive age (WRA, n = 802) had plasma Se concentrations below the thresholds for the optimal activity of the selenoproteins glutathione peroxidase 3 (GPx3; <86.9 ng mL−1) and iodothyronine deiodinase (IDI; <64.8 ng mL−1), respectively. This is the first nationally representative evidence of widespread Se deficiency in SSA. Geostatistical modelling shows that Se deficiency risks are influenced by soil type, and also by proximity to Lake Malawi where more fish is likely to be consumed. Selenium deficiency should be quantified more widely in existing national micronutrient surveillance programmes in SSA given the marginal additional cost this would incur.

Highlights

More than 800 million people have insufficient dietary energy intake globally, with >2 billion people at risk of one or more micronutrient deficiencies (MNDs), or Hidden Hunger[1]
Plasma Se concentration increased with age, ranging from a median of 57.7 ng mL−1 (±26.2 ng mL−1 standard deviation (SD)) in PSC, to 81.9 ng mL−1 (±27.9 ng mL−1 SD) in adult men (Table 1)
To estimate Se deficiency prevalence, we determined the proportion of WRA and men whose plasma Se concentration was less than thresholds previously established for the optimal activities of two essential selenoproteins, glutathione peroxidase 3 (GPx3) and iodothyronine deiodinase (IDI), involved in oxidative stress response and thyroid function, respectively[9]

Summary

Introduction

More than 800 million people have insufficient dietary energy intake globally, with >2 billion people at risk of one or more micronutrient deficiencies (MNDs), or Hidden Hunger[1]. Small-scale cross-sectional studies of food intakes[10,11], composite diets[10], and Se status in blood plasma among the Malawi population are consistent with predictions that the majority of the Malawian population are Se deficient[10,12]. Conditional distributions of Se status could be computed from this model at unsampled sites and, from these, both the expected status and the probabilities that plasma Se concentration of WRA was

Objectives

Methods

Results