December 27, 2011 by  
Filed under Elements

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Keywords: glutathione peroxidase, mercury detoxification, anti-infection, anti-virus


  • Anti-carcinogenic
  • DNA repair
  • Needed by the immune system
  • Needed for glutathione peroxidase enzyme
  • Needed for thyroid hormone activation
  • Prostaglandin production
  • Spares vitamin E

Good food sources

  • Brazil nuts
  • Cereals (but not in Western Europe or New Zealand)
  • Fish and shellfish
  • Meat and offal (depending on the selenium levels in the feed used)

Deficiency signs and symptoms

  • Age spots
  • Cancerous changes
  • Cataracts
  • Growth impairment
  • Heart disease
  • Infections
  • Muscle inflammation
  • Pale fingernail beds
  • Pancreatic insufficiency
  • Reduced detoxification ability
  • Reduced fertility in males
  • Susceptibility to virus infections

Preventing deficiency

Soil levels of selenium vary considerably in different parts of the world. Most areas of the UK, New Zealand, Finland and parts of China are very selenium-poor. A high proportion of the UK’s selenium intake used to come from selenium-rich Canadian wheat. In recent years European wheat is being used instead, and the UK’s average selenium intake has dropped to only 30 micrograms per day, well below the Lower Reference Nutrient Intake—the official deficiency level.

Selenium adequacy is tested for by measuring the activity of the important antioxidant enzyme glutathione peroxidase. In a 1990 UK study, it was found that 25 per cent of healthy volunteers and 50 per cent of medical patients had serum selenium values below those required for full expression of glutathione peroxidase activity (Pearson DJ et al: Human selenium status and glutathione peroxidase activity in north-west England. Eur J Clin Nutr 1990;44(4):277-83.)

Despite this and other studies, the UK Government does not warn against selenium deficiency nor enforce the addition of selenium to fertilizer, a practice now successfully used in Finland.

One of the richest sources of selenium is Brazil nuts. If either fish, meat, offal or brazil nuts are not consumed daily in low-selenium countries, it is probably wise to take a daily selenium supplement.


Because animals grazing in very high-selenium areas can suffer symptoms of selenium poisoning, it is believed that there is a very narrow margin between selenium adequacy and selenium toxicity. This has encouraged the belief that the use of selenium supplements should be discouraged.

Information compiled by Linda Lazarides
Naturopathic Nutritionist, Author, Educator


December 11, 2001 by  
Filed under Database

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Thyroid hormone

The thyroid gland secretes three different hormones. One, calcitonin, is involved in blood calcium regulation. The other two, thyroxine (T4) and tri-iodothyronine (T3) are known together as thyroid hormone and are involved in growth and energy metabolism. T3 is the more active form of thyroid hormone. T4 is converted to T3 by a selenium-dependent process. Iodine, vitamin A and the amino acid tyrosine are required for the synthesis of thyroid hormone. It is thought that thyroid hormone plays a part in the conversion of beta-carotene to vitamin A since hypothyroidism, the thyroid deficiency disease, result in high levels of beta carotene in the blood (hypercarotenaemia).