- Open Access
- Open Peer Review
Serum concentration of Selenium in healthy individuals living in Tehran
© Safaralizadeh et al; licensee BioMed Central Ltd. 2005
- Received: 08 June 2005
- Accepted: 14 November 2005
- Published: 14 November 2005
To investigate whether daily diet provides adequate selenium intake in healthy men and women living in Tehran, Iran.
Serum level of selenium was determined in 184 healthy individuals of both genders. The samples were divided into two age groups, adults and children, for analysis. The serum level of selenium was determined using hydride generation and flame atomic absorption spectroscopy.
The mean and standard deviation of serum selenium levels in children (1–16 years) was 84.3 ± 11 μg/l and there was no significant difference between genders in this group. In adults (older than 16 years) the mean serum selenium level was 100.6 ± 13 SD μg/l; among women the mean was 93.9 ± 14 SD μg/l and among men it was 102.2 ± 12 SD μg/l. The mean selenium level in men was higher than in women and data analysis showed a significant difference between them (p < 0.005). There was also a positive correlation between higher selenium serum concentration and age in men (P < 0.001). Daily intake of selenium in men and women was calculated to be 67 μg and 62.1 μg respectively.
Our results show that the serum concentration of selenium in an Iranian population is similar to other nationalities in the Middle East, particularly Saudi Arabia.
- Tehran inhabitants
Selenium (Se) plays a key role in the maintenance of normal health in human populations . The cellular biochemistry of Selenium involves the expression of a variety of selenoproteins. Selenium is part of the active site of glutathione peroxidase (GSH-Px), an antioxidant enzyme . It has been demonstrated that, when taken as a supplement, Selenium modulates the cellular response to oxidative stress, inducing a faster restoration of the endogenous antioxidative defense system against the production of reactive oxygen species . Glutathion peroxidase controls the interacellular level of hydrogen peroxide, reducing the formation of reactive oxygen species that can induce lipid peroxidations with consequent damage to the cellular membranes . Epidemiological studies suggest a low intake of Selenium might predispose an individual to an increased incidence of cardiovascular disorders . There is increasing evidence that selenium deficiency may have several serious short- and long-term medical implications, including impaired immune response, or even cancer . An experimental study has shown that an increase in selenium level is associated with decreased cancer mortality . The recommended dietary allowance of Selenium in the USA is 55 μg/day for women and 70 μg/day for men. In some regions of the world such as Finland, New Zealand, the East coast of the United States of America and China the content of Selenium in soil is remarkably low . Therefore Selenium levels in the serum of populations throughout the world vary from 41.7 μg/l in Finland to 158.2 μg/l in Canada . There is currently no information of selenium intake and serum levels in the Iranian population. The aim of our study was therefore to evaluate serum levels of Selenium to find out whether daily diet provides adequate selenium intake to maintain the health of men and women living in Tehran.
1. Subject selection
Serum samples were collected from 184 random inhabitants of Tehran. An informed consent was acquired, according to the guidelines from the Tehran university research ethic committee. Some of the samples were collected from excessive serum residues of blood taken from children who were referred for routine laboratory check up at the Children's Medical Center. All the samples were tested to rule out HIV, HBV and HCV contamination. Blood samples were left to coagulate spontaneously.
2. Determination of serum selenium
Blood samples (3 ml) were centrifuged at 3000 × g for 5 minutes. The clean serum was stored at -70°C until the time of analysis. All glassware and bottles used for the isolation of serum and for analysis were previously soaked in diluted nitric acid (10%) and rinsed thoroughly with deionized water. This procedure was followed in order to exclude the possibility of contamination with trace elements. Serum (500 μl) was aliquoted into a vessel-tube for mineralization with 3 ml of HNO3/HCLO4 (4:1 v/v). The temperature of this mixture was slowly increased to 175°C until fumes of HCLO4 appeared. The mixture was then heated according to the following (temperature/time) scheme: 175°C/60 min, 200°C/60 min and finally 250°C for 60 min. The mixture was then left to cool down to room temperature. HCL 6 N (10 ml) was added and heated to 170°C for 30 min to reduce the Se (VI) to Se (IV). After cooling to room temperature, Se concentration was determined using the hydride generation atomic absorption spectrometry (Atomic absorption spectrometer Shimadzu, AA-680). Sodium borohydride solution (3 g NaBH4, 1 g NaOH in 100 ml of mili-Q water) was used as a reducing agent. All samples and standards were analysed in duplicate. The accuracy of the procedure was evaluated by analyzing commercially available samples of lyophilized human serum seronorm™ trace element serum, level 1, M10181 indicating a recommended value of 81 μg/l, and seronorm™ trace element serum, level 2, NO0371 indicating a recommended value of 136 μg/l.
3. Statistical analysis
Kolmogorov-Smirnov tests were carried out for normal distribution. The reference range for serum selenium was determined as the 95% confidence interval (CI) of means. Differences in selenium concentration between the male and female populations were analyzed with the Mann-Whitney U-test. P-values of less than 0.05 were considered significant.
Age and sex of the studied individuals with corresponding selenium levels (μg/l)
Mean ± SD
Reference Range (95% CI)
85.0 ± 10.8
83.7 ± 11.1
93.9 ± 13.6
102.1 ± 12.2
Sensitivity and precision of the assay
Seronorm™ Trace Element Serum (Level 1, M10181)
81 ± 1.5
80.4 ± 2.7
Seronorm™ Trace Element Serum (Level 2, NO0371)
136 ± 4.5
135 ± 3.8
Selenium is an essential mineral in human nutrition. Natural selenium present in the diet of humans is in the form of organic seleno-proteins such as selenomethionine and seleno-cysteine. Foods such as fish and whole grain cereals are especially rich in organic selenium compounds . Selenium in cereals is primarily in the form of selenomethionine. This naturally occurring amino acid is the most important nutritional form of selenium.
Comparison of the mean serum levels of selenium, among children from different countries (as mentioned previously )
Overall mean (μg/l)
Age range (years)
The mean serum Se level for adults observed in this study was 100.6 ± 12.8 μg/l, which was similar to the one reported in a survey in Saudi Arabia . In the Nutritional Prevention of Cancer (NPC) Trial , a Selenium level of 80 ng/mL is considered the minimum level of plasma selenium necessary in the bloodstream for maximum production of selenoproteins (glutathione peroxidases, thioredoxin reductase, etc.).
Our results show that in adults there is a significant difference between men and women (p < 0.005) with a higher concentration of selenium in men. This suggests a sex-linked hormonal influence over serum level of selenium. It has previously been shown that selenium is essential for spermatogenesis . This trace element is present in the protein of the capsule surrounding the sperm mitochondria and may have a structural function . Our data also show a positive correlation between a higher concentration of selenium in serum and age in men (P < 0.001).
Comparison of the mean serum levels of selenium, among adults from different countries (as mentioned previously [9, 11])
Overall mean (μg/l)
New Zealand (Dunedin)
Brazil (Rio de Janeiro)
W. Germany (Mainz)
Considering the American RDA, which recommends a daily Se intake of 50 μg for women and 70 μg for men, it seems that the normal Iranian diet has an adequate content of selenium for both genders.
Tehran, the capital of Iran, is located in the north of the country and has a population of approximately fifteen million people, representing a large proportion of the country's total population, estimated to be seventy five million people. The diversity of nourishment sources, regional variation and different ethnic diets makes it difficult to extend these results to the whole population.
This study was supported in part by a grant from the Tehran University of Medical Sciences. The authors would like to acknowledge Dr. Verity A. Cadd at Oxford University for kind revision of the manuscript.
- Savarino L, Granchi D, Ciapetti G, Cenni E, Ravaglia G, Forti P, Maioli F, Mattioli R: Serum concentrations of zinc and selenium in elderly people: results in healthy nonagenarians/centenarians. Exp Gerontol. 2001, 36: 327-39. 10.1016/S0531-5565(00)00218-7.View ArticlePubMedGoogle Scholar
- Rotruck JT, Pope AL, Ganther HE, Swanson AB, Hafeman DG, Hoekstra WG: Selenium: biochemical role as a component of glutathione peroxidase. Science. 1973, 179: 588-90.View ArticlePubMedGoogle Scholar
- Jozanov-Stankov O, Demajo M, Djujic I, Mandic M: Selenium intake as a modulator of responsiveness to oxidative stress. J Environ Pathol Toxicol Oncol. 1998, 17: 251-7.PubMedGoogle Scholar
- Burk RF, Levander OA: Selenium. Modern nutrition in health and disease. Edited by: Shils ME, Olson J, Shike M. 1999, Lippincott Williams & Wilkins, Baltimore, 265-276. 9Google Scholar
- Salonen JT, Alfthan G, Huttunen JK, Pikkarainen J, Puska P: Association between cardiovascular death and myocardial infarction and serum selenium in a matched-pair longitudinal study. Lancet. 1982, 2: 175-9. 10.1016/S0140-6736(82)91028-5.View ArticlePubMedGoogle Scholar
- Kohrle J, Brigelius-Flohe R, Bock A, Gartner R, Meyer O, Flohe L: Selenium in biology: facts and medical perspectives. Biol Chem. 2000, 381: 849-64. 10.1515/BC.2000.107.View ArticleGoogle Scholar
- Gupta S, Narang R, Krishnaswami K, Yadav S: Plasma selenium level in cancer patients. Indian J Cancer. 1994, 31: 192-7.PubMedGoogle Scholar
- Lockitch G: Selenium: clinical significance and analytical concepts. Crit Rev Clin Lab Sci. 1989, 27: 483-541.View ArticlePubMedGoogle Scholar
- Muntau AC, Streiter M, Kappler M, Roschinger W, Schmid I, Rehnert A, Schramel P, Roscher AA: Age-related reference values for serum selenium concentrations in infants and children. Clin Chem. 2002, 48: 555-60.PubMedGoogle Scholar
- da Cunha S, Filho FM, Antelo DS, de Souza MM: Serum sample levels of selenium and copper in healthy volunteers living in Rio de Janeiro city. Sci Total Environ. 2003, 301: 51-4. 10.1016/S0048-9697(02)00290-5.View ArticlePubMedGoogle Scholar
- Schrauzer GN, Katz RN: Reductive dechlorination and degradation of mirex and kepone with Vitamin B12. Bioinorg Chem. 1978, 9: 123-43. 10.1016/S0006-3061(00)80285-9.View ArticlePubMedGoogle Scholar
- Vanderpas JB, Contempre B, Duale NL, Goossens W, Bebe N, Thorpe R, Ntambue K, Dumont J, Thilly CH, Diplock AT: Iodine and selenium deficiency associated with cretinism in northern Zaire. Am J Clin Nutr. 1990, 52: 1087-93.PubMedGoogle Scholar
- DeLong GR, Leslie PW, Wang SH, Jiang XM, Zhang ML, Rakeman M, Jiang JY, Ma T, Cao XY: Effect on infant mortality of iodination of irrigation water in a severely iodine-deficient area of China. Lancet. 1997, 350: 771-3. 10.1016/S0140-6736(96)12365-5.View ArticlePubMedGoogle Scholar
- Napolitano G, Bonomini M, Bomba G, Bucci I, Todisco V, Albertazzi A, Monaco F: Thyroid function and plasma selenium in chronic uremic patients on hemodialysis treatment. Biol Trace Elem Res. 1996, 55: 221-30.View ArticlePubMedGoogle Scholar
- Zimmermann MB, Adou P, Toressani T, Zeder C, Hurrel RF: Effect of oral iodized oil on thyroid size and thyroid hormone metabolism in children with concurrent selenium and iodine deficiency. Eur J Clin Nutr. 2000, 54: 209-13. 10.1038/sj.ejcn.1600921.View ArticlePubMedGoogle Scholar
- Raines DA, Kinsara AJ, Eid Fawzy M, Vasudevan S, Mohamed GE, Legayada ES, Al-Rawithi S, El-Yazigi A: Plasma and urinary selenium in Saudi Arabian patients with dilated cardiomyopathy. Biol Trace Elem Res. 1999, 69: 59-68.View ArticlePubMedGoogle Scholar
- Duffield-Lillico AJ, Reid ME, Turnbull BW, Combs GF, Slate EH, Fischbach LA, Marshall JR, Clark LC: Baseline characteristics and the effect of selenium supplementation on cancer incidence in a randomized clinical trial: a summary report of the Nutritional Prevention of Cancer Trial. Cancer Epidemiol Biomarkers Prev. 2002, 11: 630-639.PubMedGoogle Scholar
- Wu SH, Oldfield JE, Whanger PD, Weswig PH: Effect of selenium, vitamin E and antioxidants on testicular function in rats. Biol Reprod. 1973, 8: 625-9.PubMedGoogle Scholar
- Hansen JC, Deguchi Y: Selenium and fertility in animals and man – a review. Acta Vet Scand. 1996, 37: 19-30.PubMedGoogle Scholar
- Navarro M, Lopez H, Ruiz ML, Gonzalez S, Perez V, Lopez MC: Determination of selenium in serum by hydride generation atomic absorption spectrometry for calculation of daily dietary intake. Sci Total Environ. 1995, 175: 245-52. 10.1016/0048-9697(95)04859-6.View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.