Selenium and the Metallic Metal

Selenium and the Metallic Metal   

Professor B.V. Ramanan

Consultant Microbiologist & Medical Content Provider

 

Introduction

Selenium, an essential trace metal element for the human existence, is a functional component of numerous proteins and enzymes linked to DNA replication, reproduction, thyroid metabolism, infection control and protection from oxidative damage (Sunde et al, 2012).

The mineral or inorganic selenium in the soil is converted into organic form by plants, typically as selenomethionine and selenocysteine that is transferred to the animals and the human population in the food chain.

Selenium as selenomethionine is generally assimilated with the amino acid methionine into various structural and functional proteins. Most of the selenium is stored in the muscle tissues apart from liver, kidney, heart, spleen, and testes (Terry and Diamond, 2012).

Sources of Selenium

Sea food, Brazil nut, meat, poultry, cereals, and dairy sources are rich sources of selenium (Chun et al). The Recommended Dietary Allowances (RDAs) for Selenium varies from 15 mcg for infants and up to 55 mcg in adults. Pregnant women and lactating mothers need 60 and 70 mcg, respectively (www.nap.edu).

Selenium Deficiency

The Keshan disease, a cardio muscular disease in the Chinese mainland reported in the 70s is a classic example of selenium deficiency. Selenium deficiency has also been established to have a role Kashin-Beck disease, a type of osteoarthritis frequently reported in Siberia and Tibet. Selenium deficiency leads to male infertility and increases the risk of Cretinism, a medical condition typified by congenital physical deformity and learning difficulties in infants (Sunde, 2010).

Selenium and the Thyroid -an Ignored Datum

Selenium plays a vital and active role in the thyroid metabolism apart from the iodine.

Research evidence shows a strong correlation between low selenium levels and thyroid function, and the risk of goitre in a mild iodine deficient cohort (Derumeaux et al, 2003). The studies have been more significant in the women population as evidenced by a cross-sectional study in Denmark that had found a significant link to low serum selenium concentration and thyroid gland volume (Rasmussen et al, 2011).

Postpartum thyroiditis is a medical condition in which a normally functioning thyroid gland gets inflamed within the first year after childbirth. Postpartum thyroiditis in the first one to four months of the onset is marked by anxiety, irritability, palpitations, weight loss, sensitivity to heat, fatigue, and insomnia in the first four months of the onset. The condition slowly progresses into a state like hypothyroidism marked by a lack of energy, cold sensitivity, constipation, dry skin, weight gain and depression (Negro et al, 2007).

Interestingly, women with postpartum thyroiditis often have been found to have high concentrations of anti-thyroid antibodies during pregnancy and post-partum leading us to the conclusion that women with thyroid peroxidase antibodies are prone to thyroid complications akin to Hashimoto's thyroiditis (Rayman, 2012). A clinical trial in a cohort of pregnant women detected with thyroid peroxidase antibodies has shown that a daily supplementation with 200 mcg selenium in the form of selenomethionine would reduce postpartum thyroiditis (Negro et al, 2007 and Reid et al, 2010).

Selenium in Cancer Prevention and Cardiovascular Health

Though the Nutritional Prevention of Cancer Trial, a double-blind, randomized, controlled trial on adults has established that a daily intake of 200 mcg/day selenium for six years can lower the risk of prostate cancer (Duffield-Lillico, 2003), FDA has not validated these results as conclusive but not refuted it either. The FDA, instead, in 2003, had approved a regulatory health label claim on foods and dietary supplements containing selenium to state that “some scientific evidence suggests that consumption of selenium may reduce the risk of certain forms of cancer” (www.fda.gov).

Seleno-proteins have been shown to prevent abnormal aggregation of platelets (Stranges et al, 2006). A randomized, placebo-controlled study in a cohort of healthy adults aged between sixty to seventy-four years has established that selenium supplements would reduce total plasma cholesterol and non–high-density-lipoprotein (HDL) plasma cholesterol (Rees et al, 2013).

Conclusion

Numerous investigations on the possible role of selenium in alleviation of the symptoms of Alzheimer’s disease (Loef et al, 2011) and other diseases are underway. Though selenium is an essential trace element as discussed, selenium interacts with Cisplatin, a drug used in chemotherapy to treat ovarian, bladder, lung, and other types of cancers and a few other drugs such as atorvastatin, warfarin, niacin, and barbiturates (Vernie et al, 1988 and Hu et al, 1997). Ingestion of abnormally higher doses of selenium is deleterious (MacFarquhar et al, 2010) and hence, it is good to take the advice of a health care provider to decide upon the right dose.


Reference

1.      Sunde RA. Selenium In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:711-8

2.      Sunde RA. Selenium. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2012:225-37.

3.   Terry EN, Diamond AM. Selenium. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012:568-87.

4.      Chun OK, Floegel A, Chung SJ, Chung CE, Song WO, Koo SI. Estimation of antioxidant intakes from diet and supplements in U.S. adults. J Nutr 2010; 140:317-24.

5.      Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: Vitamin C, Vitamin E, Selenium, and Carotenoids. National Academy Press, Washington, DC, 2000.

6.      Derumeaux H, Valeix P, Castetbon K, Bensimon M, Boutron-Ruault MC, Arnaud J, Hercberg S. Association of selenium with thyroid volume and echostructure in 35- to 60-year-old French adults. Eur J Endocrinol 2003;148(3):309-15.

7.      Rasmussen LB, Schomburg L, Kohrle J, Pedersen IB, Hollenbach B, Hog A, et al. Selenium status, thyroid volume, and multiple nodule formation in an area with mild iodine deficiency. Eur J Endocrinol 2011; 164:585-90.

8.      Negro R, Greco G, Mangieri T, Pezzarossa A, Dazzi D, Hassan H. The influence of selenium supplementation on postpartum thyroid status in pregnant women with thyroid peroxidase autoantibodies. J Clin Endocrinol Metab 2007; 92:1263-8.

9.      Reid SM, Middleton P, Cossich MC, Crowther CA. Interventions for clinical and subclinical hypothyroidism in pregnancy. Cochrane Database Syst Rev 2010:CD007752.

10.  Rayman MP. Selenium and human health. Lancet 2012; 379:1256-68.

11.  Duffield-Lillico AJ, Dalkin BL, Reid ME, Turnbull BW, Slate EH, Jacobs ET, et al. Selenium supplementation, baseline plasma selenium status and incidence of prostate cancer: an analysis of the complete treatment period of the Nutritional Prevention of Cancer Trial. BJU Int 2003; 91:608-12.

12.  U.S. Food and Drug Administration. Qualified Health Claims: Letters of Enforcement Discretion. Available at https://www.fda.gov/food/food-labeling-nutrition/qualified-health-claims-letters-enforcement-discretion. Accessed on 26 April 2021.

13.  Stranges S, Marshall JR, Trevisan M, Natarajan R, Donahue RP, Combs GF, et al. Effects of selenium supplementation on cardiovascular disease incidence and mortality: secondary analyses in a randomized clinical trial. Am J Epidemiol 2006; 163:694-9.

14.  Rees K, Hartley L, Day C, Flowers N, Clarke A, Stranges S. Selenium supplementation for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2013 Jan 31;(1):CD009671.

15.  Vernie LN, de Goeij JJ, Zegers C, de Vries M, Baldew GS, McVie JG. Cisplatin-induced changes of selenium levels and glutathione peroxidase activities in blood of testis tumor patients. Cancer Lett 1988; 40:83-91.

16.  Hu YJ, Chen Y, Zhang YQ, Zhou MZ, Song XM, Zhang BZ, et al. The protective role of selenium on the toxicity of cisplatin-contained chemotherapy regimen in cancer patients. Biol Trace Elem Res 1997; 56:331-41.

17.  Loef M, Schrauzer GN, Walach H. Selenium and Alzheimer’s disease: a systematic review. J Alzheimers Dis 2011; 26:81-104.

18.  Thomson CD, Chisholm A, McLachlan SK, Campbell JM. Brazil nuts: an effective way to improve selenium status. Am J Clin Nutr. 2008 Feb;87(2):379-84.

19.  MacFarquhar JK, Broussard DL, Melstrom P, Hutchinson R, Wolkin A, Martin C, et al. Acute selenium toxicity associated with a dietary supplement. Arch Intern Med 2010; 170:256-61.


Note: This is not medical advice and these statements have not been evaluated by the FDA, if you have any concerns about your health please speak with your doctor

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