Selenium isn’t a mineral that receives a lot of press attention, however it is an essential trace element that is incredibly vital to our health. I first became aware of the importance of selenium for optimal health when I was studying for my MSc in Nutritional Medicine at the University of Surrey. My professor at that time, Margaret Rayman, was (and is) a leading scientific researcher in the field of selenium. At the time I was studying (2000-2002) there was a lot of research linking low selenium intakes to increased prostate cancer risk in men. A very recently published paper (1) has now found that low selenium intakes seem to be tied to throat and stomach cancers too. This is a preliminary study and further research is certainly required before any firm conclusions can be drawn.
Selenium acts as an important antioxidant in the body and this may account for part of the role it plays in cancer prevention. As an antioxidant selenium may also be useful in preventing conditions related to inflammation such as pancreatitis, rheumatoid arthritis, systemic inflammatory response syndrome, asthma and cardiovascular disease, to name but a few. It is also vital for a healthy immune system and plays a role in fertility in men and women. In men it is vital for good sperm motility and in women selenium appears to be vital in very early pregnancy (2)
With regards the potential cancer protective role of selenium the antioxidant role may not be the only way that selenium acts. Selenium also seems to act at the DNA level on specific genes in a variety of complicated ways (2)
As well as the requirement of selenium for antioxidant defence there is evidence that selenium:
* Is needed for thyroid function
* Is required by the immune system
* Has important antiviral effects
* Is needed for reproduction
* Enhances mood
* Reduces the risk of cancer
* Protects against mercury toxicity
The effect of selenium and its importance is most observable in populations where selenium status is low. The amount of selenium in the soil where food is grown determines its selenium content. This is important here in the UK since our soils are very low in selenium. The UK RNI (reference nutrient intake) for selenium is 75mcg/d for adult men and 60mcg/d for adult women. However in the UK selenium intakes are estimated to be 39mcg/d which is very low and probably inadequate for most individuals (3). Selenium intakes in the UK have fallen over the last 25 years largely due to the decrease in imports of high selenium wheat from the USA and Canada. Plant foods are generally low in selenium in the UK/Europe where soil selenium levels are low (2).
Care is needed with supplementation since high doses of selenium can build up in the body and are toxic to health. I would suggest not taking more that 100mcg/d. I also do not recommend taking selenium as a single nutrient supplement since nutrients interact in complex and synergistic ways. If you are taking a multi-vitamin and mineral supplement check to see that it contains selenium, if not then consider switching to a multi-formulation that does contain selenium. Unfortunately dietary sources of selenium are few in the UK. Brazil nuts (just 4-6 a day) and fish contain the highest concentrations in the diet of the UK population. Some selenium rich flours are available to buy for cooking with
(1)Steevens J et al. 2009. Selenium status and the risk of esophageal and gastric cancer subtypes: the Netherlands cohort study. Accepted Manuscript, 14 December 2009. Gastroenterology. DOI: 10.1053/j.gastro.2009.12.004
(2) Rayman, M.P. 2000. The importance of selenium to human health. The Lancet 356: 233-241.
(3) BNF (British Nutrition Foundation). 2001. Briefing Paper: Selenium and Health.
Written by Ani Kowal
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