Selenium in the Environment, Metabolism and Involvement in Body Functions

Abstract

Selenium (Se 34 79 ) is a metalloid which is close to sulfur (S) in terms of properties. The Se concentration in soil varies with type, texture and organic matter content of the soil and with rainfall. Its assimilation by plants is influenced by the physico-chemical properties of the soil (redox status, pH and microbial activity). The presence of Se in the atmosphere is linked to natural and anthropogenic activities. Selenoproteins, in which selenium is present as selenocysteine, present an important role in many body functions, such as antioxidant defense and the formation of thyroid hormones. Some selenoprotein metabolites play a role in cancer prevention. In the immune system, selenium stimulates antibody formation and activity of helper T cells, cytotoxic T cells and Natural Killer (NK) cells. The mechanisms of intestinal absorption of selenium differ depending on the chemical form of the element. Selenium is mainly absorbed in the duodenum and caecum by active transport through a sodium pump. The recommended daily intake of selenium varies from 60 μg/day for women, to 70 μg/day for men. In growing ruminants the requirements are estimated at 100 μg/kg dry matter and 200 μg/Kg for pregnant or lactating females. A deficiency can cause reproductive disorders in humans and animals.

Selenium behavior in the soil environment and its implication for human health

“…In several regions in the world, soils present low Se availability, resulting in diseases and disorders related to Se deficiency in human organism (Combs, 2001;Mehdi et al, 2013). Selenium deficient soils are found in UK, Australia, central Siberia, New Zealand, Thailand, Africa, Finland, Turkey, Nepal, northeast to south central of China, Denmark, and parts of Bangladesh and India, among others (Rahman et al, 2013;Yasin et al, 2015).…”

“…Inadequate intake of Se, added with iron (Fe), zinc (Zn) and iodine (I), vitamin A and vitamin B-12, become a malnutrition problem in a large proportion of the world' population (Combs, 2000;White and Broadley, 2009;Miller and Welch, 2013). The dietary Se intake in a region is influenced greatly by the food Se contents, which in turn is closely linked with the availability of the element in the environment, especially in the soil (Pietinen et al, 2010;FairweatherTait et al, 2011;Mehdi et al, 2013). Thus, researches that have addressed the question of the geochemical behavior of Se in soils has increased in the last decades.…”

“…It was discovered in 1817 by Swedish chemist Jons Jakob Berzelius, who named the new element from the Greek word 'Selene', meaning Goddess of the Moon (Terry et al, 2000). Selenium is widely used in industry for the manufacture of several products, such as semiconductors, rectifiers, photovoltaic cells (because of its ability to convert light energy into electrical energy), corrosion-resistant alloys, pharmaceutical substances, and pigments (red and orange color) for paints, ceramics, and glass-making process (Mehdi et al, 2013).…”

Prevalence of Urinary Tract Infections among First Grade Primary School Children in Gorgan, Northeast of Iran

“…Bacteriuria was still present in 60% of children for 9 months after the third screening [14]. The study of Elo et al showed that UTI in females aged 10-11 years is mainly asymptomatic; therefore, primary school children are at higher risk of developing such infections [15]. Some studies demonstrated that almost 10% of children with UTI would develop renal scarring [16].…”

“…It is divided into different types that can be referred to complex vs. non-complex, upper vs. lower and symptomatic vs. asymptomatic [1,2]. UTI is the second most common infection among children, and is categorized into primary and recurrent infection, based on the functional objectives [3,4].…”