There's some hype around selenium at the moment and as with any topical issue, the lines between fact and fiction are blurring - so here's what you need to know about selenium, and its relationship to eating seafood, and mercury toxicity.
What is it? A non-metal, rare chemical element which exists in organic and inorganic forms.
Why do we need it? Selenium is a micronutrient essential to cellular function. It plays a role in immune system function and thyroid function. It combines with proteins to form selenoproteins, which act to prevent and protect against cellular damage from free radicals (natural byproducts of oxygen metabolism), thereby reducing the risk of developing chronic diseases such as cancer and cardiovascular disease.
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Where can I get it? Your body's needs can be met by a well balanced diet, supplementation is rarely necessary. Dietary sources include brazil nuts, seafood, poultry, organ meats, eggs, mushrooms and cereals; plant food levels of selenium vary depending on the soil concentrations where it was grown, there is less variation in animal sources.
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Could I be deficient? Selenium deficiency is rare, if in doubt check with your health professional or check the Recommended Daily Intake. It has been suggested that a selenium deficiency primarily puts one at risk of developing Keshan disease and Kashin-Beck disease, which adversely affect the heart, joints and bones.
Can I have too much? Although rare, selenium toxicity can occur resulting in selenosis, a condition characterised by garlic smelling breath, brittle hair and fingernails, hair loss, fatigue, and irritability; so don't start gorging on mountains of brazil nuts, moderation is key.
Selenium, seafood and mercury The threat of mercury toxicity has elicited a reduction in the amount of fish and seafood being consumed - some may argue this is beneficial for our oceans and ecosystems - but as far as mercury toxicity goes, recent studies have shown that the selenium content in fish protects the consumer against potential damage from mercury.
Selenium in the body is easily bound and made useless by mercury, the trick is to consume more selenium than mercury. It is believed the selenium doesn't necessarily have to be consumed with the mercury, as long as your diet includes adequate selenium sources and you have healthy levels. To be safe, be aware of the mercury levels in different fish.