Selenium levels are frequently low in the soils of some regions and in certain Western diets. There appears to be problems associated with selenium deficiency; however, no clearly defined selenium deficiency syndrome has been accepted, although several theories postulate such a syndrome and evidence to support them seems to be mounting. Given selenium's many important functions and uses, its deficiency may generate increases in many of the disease states that it can prevent and treat. With selenium deficiency, there may be increased risk and rates of certain cancers, cardiovascular disease, hypertension, strokes, myocardial infarction, and kidney disease-all heavyweights along death row. Other problems possibly associated with selenium deficiency include eczema, psoriasis, rheumatoid arthritis, cataracts, cervical dysplasia, alcoholism, and infections. As I have discussed, low soil selenium is related to higher cancer rates, and Keshan disease is likely a direct result of selenium deficiency.
Selenium deficiency is more common, of course, in areas of low soil selenium and also in infants fed cow's milk instead of breast milk. Selenium absorption may be reduced with aging; in addition, older people often consume less selenium-containing fresh and whole foods.
Cataracts have been shown to contain only about one-sixth as much selenium as a normal lens; research is needed to determine whether this is a cause or a result of the cataract. Many books describe more rapid aging and decreased tissue elasticity with selenium deficiency, but this has not been confirmed with solid evidence. Many other metals, including cadmium, arsenic, silver, copper, and mercury, are thought to be more toxic in the presence of selenium deficiency.
We need to find better ways to evaluate body levels of selenium. Blood levels are not easy to evaluate, as they are low and much of selenium is stored. Hair analysis is not very reliable for selenium. Until we find reasonably priced testing methods that correlate accurately with tissue levels and health status, it is wise to take additional selenium as outlined here, unless one lives in a selenium-rich area.
Requirements: Like many of the trace minerals, there is no specific RDA for selenium. The usual suggested intake is between 50 and 200 mcg., which is also the range provided by the average diet of wholesome foods and water. Selenium is increasingly available in vitamin-mineral supplements and is part of all nutritional antioxidant formulae.
The conservative safe amount of selenium is between 100-200 mcg. per day for adults and about 30-150 mcg. per day for children, depending on age. Men may need more selenium, especially when sexually active. I usually suggest no more than 200-400 mcg. per day in supplemental form, though some people do take more. Studies have used 1 mg. per day for extended periods without any adverse effects. It is likely that we need more than 100 mcg. daily to support some of selenium's functions, such as its antioxidant, anticarcinogenic, and immunostimulating effects, though further research is needed to confirm this.
Some of these functions may be best performed with the help of vitamin E; the antioxidant effects of selenium and E are synergistic. There is also a concern that vitamin C may inactivate selenium in the stomach or small intestine. This is not the case with organic selenium, selenocysteine or selenomethione, but it seems that vitamin C combines with sodium selenite and may make the selenium formed by this interaction less absorbable and possibly more toxic. So for improved function, it is wise to take selenium in the absence of vitamin C and along with vitamin E.