Selenium (Se)

Selenium first attracted attention back in the 1930's as a toxic trace element that caused hair loss and blind staggers in livestock consuming plants that had high concentrations of selenium in South Dakota¹. However in modern times selenium has now been recognised for over 40 years to be an essential mineral in human nutrition that assist in optimising health and maintaining general wellbeing.

Selenium occurs in all human organs at very low concentrations however higher concentrations of selenium are found in the liver, kidneys and pancreas. In men, there are also higher concentrations of selenium found within the testes and seminal vesicles²

Selenium plays an important role in one of the most powerful antioxidant systems within the body. It interacts with vitamin E to prevent the free radicals that are produced during oxygen metabolism, from damaging body fat and other tissues³. Selenium is also important in a number of cellular functions including cell growth and in the transformation and recycling of vitamin C, another powerful antioxidant⁴⁵.

The potential role of selenium in cancer prevention is well established however few intervention studies have been done to date. One study that included 34,000 men published in 1998, showed that men with high selenium intakes were protective against prostate cancer⁶. There is also growing evidence that selenium may reduce the risk of lung, stomach, oesophageal and colorectal cancers however there are also some studies that suggest that selenium may have a negative effect on skin cancer⁴. Although further studies need to be conducted before any real conclusions can be made, at this stage supplement mixtures containing selenium along with other antioxidants such as vitamin E, vitamin C and beta-carotene appear to be most protective⁴.

Selenium deficiencies are rare, however may be more common in areas where soils have been overworked and / or are low in the mineral for example New Zealand, Finland and some areas of China ¹. Although there is limited data selenium toxicity can also occur and there have been cases among people taking high doses; symptoms include nausea, diarrhoea, fatigue, skin and nerve damage, and loss of hair and nails^3,4.

Foods that are high in selenium include brazil nuts, seafood, some meats and fish, wholegrain products, oats and brown rice³. Most of our selenium demands are met through plants foods in our diet however the selenium content of plant foods will vary depending on the content of selenium in the soil.

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6. Yoshizawa K, Willett WC, Morris SJ, Stampfer MJ, Spiegelman D, Rimm EB, Giovannucci E. Study of prediagnostic selenium levels in toenails and the risk of advanced prostate cancer. J Natl Cancer Inst 1998; 90:1219–1224.