Minerals and trace elements - Selenium
The main function of selenium is as a component of some of the important antioxidant enzymes (e.g. glutathione peroxidase), and therefore to protect the body against oxidative damage. It is also necessary for the use of iodine in thyroid hormone production, for immune system function and for reproductive function.
The best characterised selenium deficiency condition is Keshan disease, a heart condition that affects children and women of child-bearing years in rural China where soils are deficient of selenium, leading to continuing low levels in the food chain.
Selenium intakes in the UK are below the DRVs but the implications of this are uncertain because of the lack of reliable biomarkers for selenium status and requirements.
In excess selenium is exceedingly toxic. Symptoms of selenosis (selenium excess) include brittle nails and hair, skin lesions and garlic odour on the breath.
Selenium is found in a variety of foods, especially Brazil nuts, bread, fish, meat and eggs. The selenium content of cereals is directly proportional to the selenium content in the soil. In the UK selenium intakes have fallen with the decline in import of North American selenium-rich wheat and the increased use of European cereals which are less rich in the mineral. However, some bread manufacturers still import wheat from North America.
© British Nutrition Foundation