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Polish selenium supplements not always labeled accurately

(21.07.2015)


Background:
Selenium is an essential mineral, too much or too little of which can have severe consequences for human health. Last year the European Food Safety Authority (EFSA) set an Adequate Intake (AI) of 70 microgram (µg) per day for adults, and an AI of 15 µg/day for infants aged 7-11 months. AIs ranged from 15 µg/day for children aged one to three years to 70 µg/day for adolescents aged 15-17 years. For breastfeeding women, 85 µg/day was set to account for the amount of selenium secreted in breast milk. The major source of Se is diet, and in many regions of the world the levels of Se in the soils generally reflect the Se status in human populations. Low soil levels in Europe mean food grown and consumed within Member States does not always provide sufficient dietary intakes.

Dietary supplementation is one possible solution to overcome deficiency in the diet. Selenium occurs in both inorganic (selenates and selenites) and organic forms (mainly selenomethionine and selenocysteine). Absorption from food depends on the chemical form with organic compounds being absorbed at approximately 85–95% compared with inorganic forms at about 40–50%.


The new study:
Polish researchers now investigated the selenium content of dietary supplements available on the Polish market. The study involved determination of dissolution time under different conditions and solubility as well as content and speciation of selenium. Altogether 86 supplements were tested with selenium content declared by the producer. Dispersal in the stomach was mimicked by dissolution in hydrochloric acid at 37°C. The extracts were analyzed by  HPLC couled to hydride-generation AAS (HPLC-HG-AAS).

From the results published in the journal Food Chemistry, the researchers concluded that declared values for total selenium content often differed from actual content.

For 60 of the products (70%), the selenium content ranged from 50% to 150% of the declared value. Ten of the samples contained just 12–30% of that declared and another eight contained up to half of the amount claimed on pack.

In 21 of the products, the selenium content determined exceeded values declared by between 110% to 150% of the declared value. In eight cases this was significantly higher at 151–280%.

The applied speciation analysis using HPLC-HG-AAS allowed determination of inorganic selenium. 36 products did not contain any inorganic selenium. In 25 preparations, Se(IV) and selenium-organic compounds were found; in  15 products, Se(VI) and selenium-organic compounds were found; in nine supplements, selenium was present as inorganic Se(IV) and Se(VI) as well as selenium-organic compounds.

It shoulds be noted that neither Polish nor EU law obliges producers to provide information about the composition and form of compounds in their product. However, in terms of bioavailability of different Se compounds for supplementation,  the use of inorganic compounds is less favorable than selenium-organic compounds.

Anyhow, most of the preparation did not comply with recommended daily intake doses and only one producer declared the recommended daily dose on pack. The researchers concluded that the label and information attached to the dietary supplement do not constitute a full or reliable source of information for consumers.

Comment:
It is worrying that Se supplement content labeling not only often lacks information but also often fails to declare the correct concentration. Such problems were noted by other researchers before (see: Bakirdere et al. 2015, Kozak et al. 2012, Cuderman et Stibilj 2010 ).
Michael Sperling




The new study:

Przemyslaw Niedzielski, Monika Rudnicka, Marcin Wachelka, Lidia Kozak, Magda Rzany, Magdalena Wozniak, Zaneta Kaskow, Selenium species in selenium fortified dietary supplements, Food Chem., 190 (2016) 454–459. doi: 10.1016/j.foodchem.2015.05.125


Analytical instrumentation:

Shimadzu (Kyoto, Japan) liquid chromatograph (LC-10A)
Varian SpectrAA 220FS AAS spectrometer (Mulgrave, Australia)


Related studies (newest first):

Sezgin Bakirdere, Mürvet Volkan, Yavuz Ataman, Speciation of Selenium in Supplements by High Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry, Anal. Lett. 48/9 (2015) 1511-1523, DOI: 10.1080/00032719.2014.986679

Joanna Zembrzuska, Henryk Matusiewicz, Halina Polkowska-Motrenko, Ewelina Chajduk, Simultaneous quantitation and identification of organic and inorganic selenium in diet supplements by liquid chromatography with tandem mass spectrometry, Food Chem., 142 (2014) 178–187. doi: 10.1016/j.foodchem.2013.05.004

Y.-J. Hsieh, S.J. Jiang, Determination of selenium compounds in food supplements using reversed-phase liquid chromatography–inductively coupled plasma mass spectrometry, Microchem. J., 110 (2013) 1–7. doi: 10.1016/j.microc.2013.01.009

C. Thiry, Y.-J. Schneider, L. Pussemier, L. De Temmerman, A. Ruttens, Selenium bioaccessibility and bioavailability in Se-enriched food supplements, Biol. Trace Elem. Res., 152 (2013) 152–160. doi: 10.1007/s12011-013-9604-0

A. Tyburska, K. Jankowski, Determination of selenium in dietary supplements by optical emission spectrometry after alkaline dissolution and subsequent headspace solid phase microextraction, J. Pharma. Biomed. Anal., 74 (2013) 268–272. doi: 10.1016/j.jpba.2012.11.011

L. Kozak, M. Rudnicka, P. Niedzielski, Determination of inorganic selenium species in dietary supplements by hyphenated analytical system HPLC–HG-AAS. Food Anal. Methods, 5 (2012) 1237–1243. doi: 10.1007/s12161-012-9365-y

Katarzyna Bierla, Joanna Szpunar, Alexandros Yiannikouris, Ryszard Lobinski,
Comprehensive speciation of selenium in selenium-rich yeast. Trends Anal. Chem., 41 (2012) 122.132. doi: 10.1016/j.trac.2012.08.006

H. Stosnach, Analytical determination of selenium in medical samples, staple food and dietary supplements by means of total reflection X-ray fluorescence spectroscopy, Spectrochim. Acta B, 65 (2010) 859–863. doi: 10.1016/j.sab.2010.07.001

Petra Cuderman, Vekoslava Stibilj, How Safe are Antioxidant Food Supplements Containing Selenium?, Acta Chim. Slov., 57 (2010) 668–676.

G. Vale, A. Rodrigues, A. Rocha, R. Rial, A.M. Mota, M.L. Gonçalves, L.P. Fonseca, J.L. Capelo, Ultrasonic assisted enzymatic digestion (USAED) coupled with high performance liquid chromatography and electrothermal atomic absorption spectrometry as a powerful tool for total selenium and selenium species control in Se-enriched food supplements, Food Chem., 121 (2010) 268–274. doi:10.1016/j.foodchem.2009.11.084

H. Goenaga-Infante, G. O’Connor, M. Rayman, R. Wahlen, J. Entwisle, P. Norris, Selenium speciation analysis of selenium-enriched supplements by HPLC with ultrasonic nebulization ICP-MS and electrospray MS/MS detection, J. Anal. At. Spectrom., 19 (2004) 1529–1538. doi: 10.1039/b411270a

Gerhard N. Schrauzer, Nutritional Selenium Supplements: Product Types, Quality, and Safety, J. Am. College Nutr., 20/1 (2001) 1-4. 



Related EVISA Resources

Link Database: Selenium and Human health
Link Database; Research projects related to selenium
Material Database: Materials for Selenium speciation analysis



Related EVISA News

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July 14, 2013: EU approves new selenium compound for use as a nutritional supplement in animals
May 12, 2011: Review: Selenium doesn't prevent cancer
May 3, 2011: New reference materials for the characterisation of selenium-enriched food products
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October 28, 2008: National Cancer Institute ends Selenium and Vitamin E Cancer Prevention Trial, or SELECT
October 6, 2005: Selenomethionine shows promising results as a protective agent against Esophageal Cancer
August 2, 2005: New CRM for Selenomethionine in yeast developed by NRC Canada is now on the market


last time modified: July 21, 2015




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