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Selenium - Se

GENERAL DESCRIPTION OF THE ELEMENT :

Selenium (metal): CAS N°: 7782-49-2

-atomic number: 34
-atomic weight: 78,96 (stable isotopes 76Se, 77Se, 78Se, 80Se, (82Se))
-melting point: 221°C
-boiling point: 685°C


IN A FEW LINES :

Selenium, like many other trace elements, is a natural constituent of the earth's crust. Its concentration in soils varies hugely among regions of the world, ranging from 0.1 µg/kg in Se deficient areas, to over 1000 mg/kg in seleniferous areas.

 

Production of Se occurs most frequently from selenide, a Se-compound which is present in sulphide ores, such as those of copper or lead. The largest human use of Se is as a (de)colouring agent in glass en ceramic manufacturing. It is also widely used as a catalyst in chemical reactions, in electronics, and in the toning of photographic prints. Biological uses of Se include the use of SeS2 as the active ingredient in some drandruff shampoos, and its use in vitamin preparations or other food supplements.

Selenium (Se)

 

Indeed, after the initial focus on Se as a potential toxic element, its essentiality as a trace nutrient (essential for good health!) became recognized in the middle of the last century. Several epidemiological studies and laboratory trials have shown that Se helps to reduce cancer risk and cardiovascular diseases, and helps to improve immune system functions. Specific cases of Se deficiency have been reported e.g. in the Keshan region of China where Se content in soil and food is extremely low (Keshan disease, characterised by an enlarged heart and a reduced heart function). In various circumstances food supplementation of Se (either as food supplement, either as Se-enriched food) has successfully been used to improve the Se -nutrition of Se-deficient people.

 

On the other hand, too high levels of Se-intake cause selenosis, a syndrome characterized by hair loss, fingernails brittleness, skin and liver damage, and, even, at higher levels, neurotoxicity. Such adverse health effects of Se have been reported among others in people and in cattle in seleniferous areas, including the northern great plains of the USA, parts of Venezuela, Colombia, India and China.

 

An important aspect related to Se-intake is that Se in food and food supplements can be present in different chemical forms or species that, after entering the human body, have not the same solubility, absorption, metabolism, and hence bioavailability. This means that the effect of Se (beneficial or toxic) depends not only on the quantity but also on the chemical form of the element.

 

Additional research is necessary to gain more insight in the conditions that lead to an optimal Se-nutrition (optimal health effect). Selenium (Se)The collection of data on Se-speciation in foodstuff on the one hand, and the determination of the most bio-active Se compounds and food sources on the other hand, may contribute to this.

 

Classification according to Regulation (EC) No 1272/2008 of 16 December 2008 :
Index number: 034-001-00-2
Acute Tox. 3*; H301: toxic if swallowed
Acute Tox. 3*; H331: toxic if inhaled
Stot Re2: H373: May cause damage to organs through prolonged or repeated exposure.

Aquatic Chronic 4; H413: May cause long lasting harmful effects to aquatic life.
Reference: Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 december 2008 on classification, labeling and packaging of substances and mixtures, amending and repealing Directives 67/548/EEC and 1999/45/EC, and amending Regulation (EC) No 1907/2006. Official Journal of the European Union L353/1.



NORMS AND LEGISLATION :

Maximum selenium content in water intended for human consumption

COUNCIL DIRECTIVE 98/83/EC of 3 November 1998 on the quality of water intended for human consumption.
The maximum selenium content in water intended for human consumption is fixed at 10µg/L.

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CONSLEG:1998L0083:20031120:EN:PDF

 

Tolerable upper intake level for selenium (UL)
The European Scientific Committee on Food has established an upper intake level of 300 µg Se/day for adults.


ROLE OF CODA-CERVA :

  • RESEARCH

Speciation research in the "Trace Elements" Unit at CODA-CERVA started in 2008, after the purchase of an LC-ICP-MS. This system allows the separation of different chemical species of an element on a chromatographic column, followed by a quantification step by means of ICP-MS.

Selenium (Se)Se-speciation and bioavailability of Se in food and food supplements' is one of the research topics in our unit. Se-species that are focused on include 2 inorganic forms, being selenite and selenate, and 3 organic species being selenomethionine (main selenocompound in crops, this Se-aminoacid is often unspecifically incorporated in proteins in place of methionine), selenocystine and methylselenocysteine (main compound in Se-accumulating plants after Se-enrichment, and potent anti-cancer agent as precursor of methylselenol).

 

This research includes the following aspects: optimization of a method for Se-speciation analysis in food using HPLC-ICP-MS, analysis of Se species in various food samples and construction of a database, development of a method for analysis of Se bioavailability using a Caco-2 cells model of intestinal barrier, analysis of bioavailability of different Se species, determination of background concentrations of Se in soils in Belgium, determination of potential relationships between soil characteristics and Se content/speciation in crops, and evaluation of the impact of Se-fertilisation on Se-speciation in crops.

Selenium (Se)

 

The results of this research should contribute to the knowledge about bio-active Se-compounds, and to the identification of types of food and/or food supplements able to provide an optimal human Se-nutrition.

 

In addition, insight will be obtained in the relationship between soil characteristics and crop quality (regarding Se-status).

 

This project is supported by the National Fund for Scientific Research (FNRS), the Belgian Science Policy (Belspo) and the Federal Agency for the Safety of the Food Chain (FASFC).

 

  • SERVICES

The activities of the Trace Element Unit at CODA-CERVA include scientific research and provision of services in the field of food safety, public and animal health.

 

We provide analytical facilities for third parties by the determination of trace elements in food and animal feed. The analyses of total As, Cd, Hg and Pb are accredited (BELAC 172-TEST) according to the International norm ISO 17025.

 

Analyses of a series of other trace elements (including Se) are also performed under the quality management system.

 

CODA-CERVA is the Belgian National Reference laboratory (NRL) for the determination of trace elements in food and animal feed.

 

TEAM OF SCIENTISTS :

Ann Ruttens
Nadia Waegeneers

Karlien Cheyns

CODA-CERVA PUBLICATIONS

2013

- Thiry, C., Pussemier, L, .Schneider, Y-J., Ruttens, A., 2013. Selenium bioaccessibility and bioavailability in Se-enriched food supplements. Biological Trace Element Research 152 (1) pp 152-160.

- Thiry, C., Ruttens, A., Pussemier, L, .Schneider, Y-J, 2013 In vitro investigation on selenium (Se) species-dependent intestinal transport and its impact on Se bioavailability. British Journal of Nutrition. 109 (12), pp 2126-2134.

- Waegeneers, N., Thiry, C., De Temmerman, L. and Ruttens, A. 2013. Predicted dietary intake of selenium by the general adult population in Belgium. Food additives and Contaminants. Part A. 30(2), pp. 278-285.

2012

- Thiry C., Ruttens A., De Temmerman L., et al., 2012. Current knowledge in species-related bioavailability of selenium in food. Food Chemistry, 130(4), pp 767-784.