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Selenium is an essential trace element that is required in human
and animal nutrition. Selenium plays an important role in defending
against toxicity of oxygen, in regulation of hormone metabolism in
the thyroid, and in the regulation of the redox state of cells. Due
to its potential toxicity and fears that it might be a carcinogen,
selenium's role in human and animal nutrition was not discovered for
many years. Many of these fears have now been replaced by evidence
suggesting that selenium may protect against some forms of cancer by
activating an antioxidant enzyme called glutathione
peroxidase.
Selenium is considered to have an important role
in promoting healthy immune function and is believed to reduce the
probability of viral hepatitis in selenium-deficient populations.
Selenium supplementation has been found to stimulate the activity of
white blood cells, primary components of the immune system, even in
selenium non-deficient populations and especially in the
elderly.
The amount of selenium in the food you eat is
directly related to the amount of selenium in the soil where the
food was grown. Selenium enters the food chain through plants as the
amino acids L-selenocysteine and L-selenomethionine from the soil
where the plant is grown. Selenium, like most trace elements and
minerals found in the soil, is not found in the same concentrations
in all regions of the world. Because of the uneven concentrations of
selenium, disorders of both selenium deficiency and selenium excess
are not uncommon. China has the highest variance of selenium
distribution, having both the highest and lowest levels soil
concentrations in the world.
Selenium Supplementation
Dosage Recommendations
Available forms of selenium
supplements are high-selenium yeast, L-selenomethionine, sodium
selenate, and sodium selenite. Recommended Dietary Allowance for
most adults is 55 mcg per day, but supplementation with 100–200 mcg
of selenium per day has been recommended by some
doctors.
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