What is Selenium?
Selenium (Se), a vital trace mineral found in the body, is needed for the proper functioning of selenoproteins, which are selenium-dependent enzymes.
The selenocysteine is incorporated into an exact location in the amino acid sequence for a functional protein to be formed during selenoprotein synthesis.
Plants do not need this trace element for survival, unlike animals. When present in soil, selenium is incorporated by plants into compounds that typically contain sulfur.
Selenium as an Antioxidant
Selenium works as an antioxidant particularly when vitamin E is combined with it that aids in fighting harmful particles known as free radicals. Free radicals can greatly damage DNA and cell membranes and plays a major role in a number of conditions such as cancer and heart disease; and can also contribute to the aging process. Antioxidants can help in neutralizing free radicals and reduces or prevents the damage they cause.
Selenium interacts with certain nutrients that can affect the cellular redox status such as pro-oxidant/antioxidant balance. Copper (as superoxide dismutase), iron (as catalase), and zinc (as superoxide dismutase) are other minerals that are known to be crucial components of antioxidant enzymes. As gluthathione peroxidase, selenium appears to support the activity of α-tocopherol, vitamin E, in limiting the oxidation of lipids.
Selenium Deficiency
Insufficient intake of selenium can result to decreased glutathione peroxidases activities as well as some other thyroid deiodinases and thioredoxin reductase. Selenium deficiency does not normally result in obvious clinical illness even in severe cases. Deficiency in selenium rarely occurs in the United States, but can be observed notably in China and in other countries, where the soil concentration of selenium is low. Certain evidence suggests that selenium deficiency contributes to the development of a form of hypothyroidism, a weakened immune system, and heart disease. It was shown that deficiency of selenium does not normally cause illnesses by itself, but it makes the body more susceptible to illnesses due to the other biochemical, nutritional, or infectious stresses.
The three particular diseases that were linked with a deficit include:
- Myxedematous Endemic Cretinism, which can result to mental retardation.
- Kashin-Beck Disease, which results in osteoarthropathy.
- Keshan Disease, which occurs in selenium deficient children that results to an enlarged heart and poor heart function.
Keshan disease was first described in China in the early 1930s and is still seen in several areas of the Chinese countryside wherein there is selenium poor soil. Researchers believe that individuals with selenium deficiency that have become infected with a certain virus are those that will most likely to develop Keshan disease. Selenium deficiency is mostly seen in patients who are relying on total parenteral nutrition (TPN) as their main nutritional source.
Severe gastrointestinal disorders can help decrease selenium absorption that results to selenium deficiency or depletion. The absorption of other nutrients can also be affected by gastrointestinal problems that impair selenium absorption, and need a routine monitoring of nutritional status in order for the proper nutritional and medical treatment to be provided.
Selenium RDA
The Food and Nutrition Board (FNB) of the Institute of Medicine revised the Recommended Dietary Allowance (RDA) in 2000 wherein it was based on the amount of dietary selenium needed to maximize the activity of the antioxidant enzyme glutathione peroxidase in plasma.
|
AGE |
(mg/day) |
| 0 to 6 months | 15 AI |
| 7to 12 months | 20 AI |
| 1 to 3 years | 20 |
| 4 to 7 years | 30 |
| 9 to 13 years | 40 |
| 14 to 18 years | 55 |
| 19 years and older | 55 |
| Pregnant all ages | 60 |
| Lactating all ages | 70 |
Selenium Rich Foods
Some of the excellent food sources of selenium include dried Brazil nuts, beef, tuna, pork, turkey, chicken, cod, oatmeal, rice, bread, walnut, cheddar cheese, macaroni, pasta, noodles, egg, salmon, halibut, crab meat, and shrimp.
Selenium-enriched vegetables are currently an interest to many scientists as the methylated forms and other forms of selenium they produce can be a more effective inhibitor of tumor formation than Selenium that is available in food supplements.