Selenium and the Metallic Metal
Professor B.V. Ramanan
Consultant Microbiologist & Medical Content Provider
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).
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).
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.
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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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