Symposium on ‘Geographical and geological influences on nutrition’ Factors controlling the distribution of selenium in the environment and their impact on health and nutrition

Abstract

Se is essential to human and animal health but can be toxic in excess. An interest in its geochemistry has developed alongside a greater understanding of its function in a number of health conditions. Geology exerts a strong control on the Se status of the surface environment; low-Se rock-types (0·05–0·09 mg Se/kg) make up the majority of rocks occurring at the Earth's surface, which in turn account for the generally low levels of Se in most soils. However, there are exceptions such as associations with sulfide mineralisation and in some types of sedimentary rocks (e.g. black shales) in which contents of Se can be much higher. Baseline geochemical data now enable a comparison to be made between environmental and human Se status, although a direct link is only likely to be seen if the population is dependent on the local environment for sustenance. This situation is demonstrated with an example from the work of the British Geological Survey in the Se-deficiency belt of China. The recent fall in the daily dietary Se intake in the UK is discussed in the context of human Se status and declining use of North American wheat in bread making. Generally, US wheat has ten times more Se than UK wheat, attributed to the fact that soils from the wheat-growing belt of America are more enriched in Se to a similar order of magnitude. In agriculture effective biofortification of crops with Se-rich fertilisers must be demonstrably safe to the environment and monitored appropriately and baseline geochemical data will enable this process to be done with confidence.

A Randomized Trial of Glutamine and Antioxidants in Critically Ill Patients

“…16,17 These differences may reflect the considerable depletion of selenium in soil observed in parts of Europe but not throughout North America. 18 We may have prescribed an insufficient dose of selenium or used an ineffective dosing schedule, since a higher-thannormal level of selenium in the blood may be associated with the best outcome 19 and an initial bolus of selenium might have been more effective than the continuous administration we used. 20 The strengths of this study include the randomized and blinded design, rigorous determination and adjudication of infection, and intention-to-treat analysis, all of which augment the internal validity of the trial.…”

Selenium in soil–plant–food systems

“…Global Se intakes (in µg day −1 ) show significant changes among various countries, whereas the average intakes are usually low (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), temperate , and sufficient (85-150) in parts of China, North America, and Europe respectively (FAO/WHO, 1998; WHO, 2011). In more details, it is found that daily dietary Se intake ranges from 7 to 4.990 µg, with mean values of 40 µg in Europe and 93 to 134 µg for women and men in the USA respectively (Rayman, 2012).…”

An initial study to assess the use of geological parent materials to predict the Se concentration in overlying soils and in five staple foodstuffs produced on them in Scotland

“…In animals, clinical signs of Sedeficiency include reduced appetite/growth/fertility and muscle weakness; generally described as white muscle disease (WMD) (Levander, 1986). In most cases, food forms the main source of Se for humans because concentrations in water and air are generally low (WHO, 1987;Fordyce, 2005;Fordyce, 2007;Johnson et al, 2010).…”

“…and acid-neutral soils are typical as in much of Northern Europe (Fordyce, 2005;Broadley et al, 2006;Johnson et al, 2010).…”