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In this article, we describe:
- the major purposes of this specific nutrient in the human body,
- its experimentally confirmed health uses,
- conventional ways to estimate nutrient status,
- nutrient’s toxicities and deficiencies,
- experimentally confirmed and approved levels of the nutrient intake for different demographics,
- dietary sources of the nutrient.
Selenium is a trace element that is nutritionally essential for humans, is a constituent of more than two dozen selenoproteins that play critical roles in reproduction, thyroid hormone metabolism, DNA synthesis, and protection from oxidative damage and infection.
Selenium exists in two forms: inorganic (selenate and selenite) and organic (selenomethionine and selenocysteine). Both forms can be good dietary sources of selenium. Soils contain inorganic selenites and selenates that plants accumulate and convert to organic forms, mostly selenocysteine and selenomethionine and their methylated derivatives.
Most selenium is in the form of selenomethionine in animal and human tissues. The most commonly used measures of selenium status are plasma and serum selenium concentrations. Concentrations in blood and urine reflect recent selenium intake. Analyses of hair or nail selenium content can be used to monitor longer-term intakes over months or years. Quantification of one or more selenoproteins (such as glutathione peroxidase and selenoprotein P) is also used as a functional measure of selenium status. Plasma or serum selenium concentrations of 8 micrograms (mcg)/dL or higher in healthy people typically meet needs for selenoprotein synthesis.
Selenium deficiency produces biochemical changes that might predispose people who experience additional stresses to develop certain illnesses . For example, selenium deficiency in combination with a second stress (possibly a viral infection) leads to Keshan disease. Selenium deficiency is also associated with male infertility and might play a role in Kashin-Beck disease, a type of osteoarthritis. Selenium deficiency could exacerbate iodine deficiency, potentially increasing the risk of cretinism in infants selenium deficiency in isolation rarely causes overt illness. The following groups are among those most likely to have inadequate intakes of selenium: people living with HIV; people undergoing kidney dialysis; and those living in selenium-deficiency areas. Inadequate selenium status might play a role in cancer, cardiovascular disease, cognitive decline, and thyroid disease.
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Chronically high intakes of the organic and inorganic forms of selenium have similar effects (for example, from Brazil nuts that contain very high amounts of selenium). Early indicators of excess intake are a garlic odor in the breath and a metallic taste in the mouth. The most common clinical signs of chronically high selenium intakes, or selenosis, are hair and nail loss or brittleness. Other symptoms include lesions of the skin and nervous system, nausea, diarrhea, skin rashes, mottled teeth, fatigue, irritability, and nervous system abnormalities.
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Recommended Dietary Allowances (RDAs) for Selenium
|Birth to 6 months||15 mcg*||15 mcg*|
|7–12 months||20 mcg*||20 mcg*|
|1–3 years||20 mcg||20 mcg|
|4–8 years||30 mcg||30 mcg|
|9–13 years||40 mcg||40 mcg|
|14–18 years||55 mcg||55 mcg||60 mcg||70 mcg|
|19–50 years||55 mcg||55 mcg||60 mcg||70 mcg|
|51+ years||55 mcg||55 mcg|
*Adequate Intake (AI)
Dietary Sources of Selenium
The major food sources of selenium in the Western diet are breads, grains, meat, poultry, fish, and eggs.
The amount of selenium in a given type of plant-based food depends on the amount of selenium in the soil and several other factors, such as soil pH, amount of organic matter in the soil, and whether the selenium is in a form that is amenable to plant uptake. As a result, selenium concentrations in plant-based foods vary widely by geographic location. Selenium concentration in soil has a smaller effect on selenium levels in animal products.
Selected Food Sources of Selenium
|Brazil nuts, 1 ounce (6–8 nuts)||544||989|
|Cooked (dry heat) yellowfin tuna, 3 ounces||92||167|
|Cooked (dry heat) halibut, 3 ounces||47||85|
|Canned in oil sardines, with bone, 3 ounces||45||82|
|Roasted ham, 3 ounces||42||76|
|Cooked shrimp, 3 ounces||40||73|
|Macaroni (enriched), 1 cup||37||67|
|Beef steak (bottom round), roasted, 3 ounces||33||60|
|Roasted boneless turkey, 3 ounces||31||56|
|Pan fried beef liver, 3 ounces||28||51|
|Roasted chicken, 3 ounces||22||40|
|Cottage cheese, 1% milkfat, 1 cup||20||36|
|Brown rice, cooked, 1 cup||19||35|
|Broiled ground beef, 3 ounces||18||33|
|Hard-boiled egg, 1 large||15||27|
|Puffed wheat (ready-to-eat cereal), fortified, 1 cup||15||27|
|Whole wheat bread, 1 slice||13||24|
|Canned baked beans, 1 cup||13||24|
|Oatmeal, cooked with water, 1 cup||13||24|
|Milk, 1% fat, 1 cup||8||15|
|Plain yogurt, 1 cup||8||15|
|Boiled lentils, 1 cup||6||11|
|White bread, 1 slice||6||11|
|Boiled spinach, ½ cup||5||9|
|Spaghetti sauce (marinara), 1 cup||4||7|
|Dry roasted cashew nuts,1 ounce||3||5|
|Corn flakes, 1 cup||2||4|
|Green peas, boiled, 1 cup||1||2|
|Bananas, sliced, ½ cup||1||2|
|Baked potato, flesh and skin, 1 potato||1||2|
|Peach, yellow, raw, 1 medium||0||0|
|Raw carrots, 1 cup||0||0|
|Iceberg lettuce, raw, 1 cup||0||0|
- *DV = Daily Value.
- The DV for selenium used for the values in in this table is 70 mcg for adults and children age 4 years and older. This DV, however, is changing to 55 mcg as the updated Nutrition and Supplement Facts labels are implemented.
- Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet.
- Elson Haas. “Staying Healthy with Nutrition”
- U.S. Department of Health & Human Services: https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/