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Nutrient Details For : Selenium

A nutrient is any element or compound necessary for or contributing to an organism's metabolism, growth, or other functioning. Click name for details Arsenic Biotin Boron Calcium Carbohydrates Carnitine Carotenoids Chloride Choline Chromium Copper Energy Fiber Fluoride Folate Iodine Iron Lipids Magnesium Manganese Molybdenum Niacin Nickel Pantothenic acid Phosphorus Phyto-chemicals Potassium Protein Riboflavin Selenium Silicon Sodium Thiamin Vanadium Vitamin A Vitamin B 12 Vitamin B 6 Vitamin C Vitamin D Vitamin E Vitamin K Zinc Further Trace Elements

Selenium (Se) is an essential trace element that functions as a component of enzymes involved in antioxidant protection and thyroid hormone metabolism but required only in small amounts

Selenium is incorporated into proteins to make selenoproteins, which are important antioxidant enzymes. The antioxidant properties of selenoproteins help prevent cellular damage from free radicals. Free radicals are natural by-products of oxygen metabolism that may contribute to the development of chronic diseases such as cancer and heart disease . Other selenoproteins help regulate thyroid function and play a role in the immune system

In several intra- and extra-cellular glutathione peroxidases, iodothyronine 5í-deiodinases, and in thioredoxin reductase, selenium is located at the active centers as the selenoamino acid, selenocysteine (SeCYS).

At least two other proteins of unknown function also contain SeCYS. Although SeCYS is an important dietary form, it is not directly incorporated into these specific selenium-proteins; instead, a co-translational process yields tRNA-bound SeCYS. In contrast, selenium as seleno-methionine is incorporated non-specifically into many proteins, as it competes with methionine in general protein synthesis. Therefore, tissues often contain both specific, as well as the nonspecific, selenium-containing proteins when both SeCYS and selenomethionine are consumed, as found in many foods.

Deficiencies:

Selenium deprivation reduces activities of the selenium-dependent enzymes. The signs in animals depend upon vitamin E status and appear only when both nutrients are limiting. They vary according to species. For example, selenium- and vitamin E-deficient animals show myopathies of skeletal (e.g., sheep, cow, horse), cardiac (pig) or smooth (dog, cow) muscle; hepatic necrosis (rat, pig); increased capillary permeability (chicken); or pancreatic acinar degeneration (chicken).

Characteristic signs of selenium deficiency have not been described in humans, but very low selenium status is a factor in the etiologies of a juvenile cardiomyopathy (Keshan Disease) and a chondrodystrophy (Kashin-Beck Disease) that occur in selenium-deficient regions of China.

Recommendations:

The Recommended Dietary Allowances are in µg/day: 0-0.5 yrs, 10; 0.5-1.0 yrs, 15; 1-6 yrs, 20; 7-10 yrs, 30; males 11-14 yrs, 40; females 11-14 yrs, 45; males and females 15-18 yrs, 50; adult males, 70; adult females, 55; pregnancy, 65; and lactation, 75.

The Reference Dose (RfD) set by the Environmental Protection Agency is 5 µg/kg body weight/day or 350 µg/day for a 70 kg individual. This intake is regarded as having no significant risk of a deleterious effect over a lifetime of exposure.

Food sources:

The most important sources in American diets are meats, fish and grains. Brazil nuts can have relatively high selenium concentrations. Foods of low protein content, including most fruits and vegetables, provide little selenium. Food selenium is absorbed with efficiencies of 60-80%; the greatest factor affecting the utilization of food selenium is its chemical form.

Toxicity:

Selenium toxicity is characterized by dermatologic lesions; selenotic animals and humans develop brittle hair and nails/hooves. Sporadic cases of selenium-poisoning have been reported involving industrial or accidental exposures to selenium-compounds.

Recent research news:

Preliminary findings suggest that selenium may have an anticancer effect in humans. Animal studies indicate that selenium deficiency may decrease the resistance of the host to infection with certain viruses.

Chemical information on Selenium

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