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Selenium and your healthOne could say that selenium (Se) is fairly popular nutrient these days, and there are a few good reasons for it. This micro-mineral has the ability to bind with toxic heavy metals (mercury, cadmium, lead, arsenic) and pull them out of your body through regular elimination channels.
Low selenium levels expose you to greater free-radical damage and compromised detox function; this translates into higher risk of cancer, lowered immune system efficiency and cardiovascular disease (due to its role in the production of prostaglandins). Also, selenium deficiency can contribute to Candida overgrowth, neurological symptoms, and, being essential for the synthesis of main thyroid hormone, low thyroid function. It can also lead to enlarged heart (cardiomyopathy), which in extreme cases can be life-threatening.However, too much of it can harm you, just like any other nutritional excess. Elevated selenium levels make vitamin E less efficient (unless it is supplemented too), and can also suppress chromium, magnesium, zinc and other important nutrients. Long-term excessive intake of selenium increases risk of shingles, enlarged prostate, reduced glucose tolerance, and others. It can also cause loss or hair and even nails.
Selenium toxicity is much more likely to occur as a consequence of consuming inorganic selenium form, obtained from sedimentary rocks. Its organic forms, found in plants and animals (selenomethionine and selenocysteine), as well as selenium yeast are generally non-toxic.
Selenium DRI (Dietary Reference Intakes, the most recent set of dietary recommendations set by the government) for an average healthy adult is set at 0.055mg (or 55μg), with short-term therapeutic doses of up to 2mg a day.
Selenium levels in foods depend directly on its soil concentration, which can vary widely. In most areas its concentration is low to moderate. Some areas, however, have very high selenium soil concentration. If unnoticed, it can adversely affect health of those consuming mostly locally produced food, especially if also taking longer-term selenium supplementation.
Still, most of us need to worry about selenium deficiency, rather than the excess, at least when it comes to its dietary supply. Unofficial estimates are that up to half of the U.S. population, possibly more, gets from their diet significantly less than the DRI for selenium. This is result of both, depleted soils and nutritionally depleted diets. Like other minerals, and nutrients in general, selenium is often lost in food processing.
Best natural selenium food sources are brazil nuts, seafood, beef, rice and whole grains.