Selenium is a trace mineral which is essential for life because it is a vital component of several major metabolic pathways. Selenium is incorporated as selenocysteine into a number of key enzymes called selenoproteins that help regulate immune system function, thyroid hormone production and antioxidant defence. Selenium deficiency is increasingly being linked to many types of cancer, in a growing body of research. If you have read my previous article about selenium (here), you will already be aware that research shows that consumption of 200 µg of selenium a day is capable of decreasing the overall cancer mortality and morbidity by around 50 %. However, research going back almost 30 years demonstrates consistently that dietary intakes of selenium are too low and that populations are deficient in selenium
For example, back in 1981 a study published in the American Journal of Clinical Nutrition1 measured selenium levels in middle aged free living Swedish people. The focus of the study was not selenium intake, but to compare vegan and a normal mixed diets for varying nutrient levels. The selenium content of the vegan diets averaged 5 µg / 1000 calories, but was slightly higher for the normal mixed diet at 18 µg / 1000 calories. On average the female vegans consumed just 6.9 µg of selenium per day, with the highest recorded selenium content being 13.3 µg per day. One woman had no detectable selenium in her diet. More worryingly 9 of the 12 male diets analysed also contained no detectable selenium. The other three diets for the men contained just 33, 47 and 66 µg.
It is not surprising that mixed diets contain more selenium than vegan diets, because products of animal origin such as fish, shellfishand viscera tend to have higher concentrations of selenium than cereals and vegetables. The study was conducted in Sweden, which is known to possess particularly selenium poor soils, as do most commercial soils in Scandinavia, Northern Europe and North America. Studies involving these regions have consistently shown that diets contain less than the recommended levels of selenium. Therefore, if you live in these areas it would appear that supplementation with 200 µg of selenium would be a prudent step towards maintaining optimum nutrition. Selenium is available as a more expensive selenomethionine amino acid chelate form. However, most of the studies have used the cheaper yeast selenium and so this is the form that is recommended.
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1Abdulla, M., Anderson, I., Asp, N., Berthelsen, K., Birkhed, D., Dencker, I., Johansson, C., Jagerstad, M., Kolar, K., Nair, B. M., Nilsson-Ehle, P., Norden, A., Rassner, S., Akesson, B. and Ockerman, P. 1981. Nutrient intake and health status of vegans. Chemical analysis of diets using the duplicate portion sampling technique. American Journal of Clinical Nutrition. 34, 2464-2477
