Selenium is an essential dietary trace mineral1,2 and is a pro oxidant3, that is an essential part of glutathione peroxidase4. It is essential because is serves to activate this antioxidant.
Dietary sources rich in selenium include: brazil nuts, tuna, beef liver, pasta, turkey, cod fish, chicken breast, roast beef, white bread, oatmeal, rice and whole eggs.
2. What does it do and what scientific studies give evidence to support this?
Selenium is a powerful substance and has many applications.
As an antioxidant, selenium provides protection from alcohol induced oxidative stress, thus helping to prevent alcohol-induced liver injury5, and reduces oxidative stress that leads to DNA damage6. Selenium has also been shown to reduce the damage inflicted on the hypocampus by the excitotoxin quinolinic acid7.
Selenium is used in the treatment of many diseases. For example, selenium has been used in the treatment of prostate cancer in men8,9 and although one study has called the cancer fighting and cancer preventing abilities of selenium into question10, ample research has shown that it may moderately reduce the risk of prostate cancer in men11, 12, 13, 14,15,16,17. It has been shown to reduce the occurance of malignant skin conditions18, improve lung function in persons with cystic fibrosis19, reduce the risk for heart disease and cancer20, and offer protection from hyperoxaluria21. Selenium also helps to prevent the onset of dementia in elderly persons22, reduce cell death resulting from ultra-violet radiation exposure23, 24 as well as helping to inhibit the spread of the HIV virus25.
Furthermore, selenium is used in the treatment of cardiovascular disease26, 27, in the treatment of arterial sclerosis28 and in the treatment of aggressive non-Hodgkin's lymphoma29 and chemoprevention30. Because of its NO inhibiting ability selenium is useful in the treatment of anti-inflamatory conditions31 and may protect the heart from inflammation32.
Selenium is an essential dietary mineral because it acts as a catalyst for many physiological processes. Selenium is neccesary for the proper functioning of the thyroid33, 34, 35, 36 and is required for the proper functioning of neutrophils, macrophages, NK cells, T lymphocytes and some other immune system activities37.
It is used in the treatment of male infertility, and can increase the motility and quality38 of sperm and increase the likeleyhood of conception39 Selenium may also protect the female reproductive system from arsenic damage40.
3. Who needs it and what are symptoms of deficiency?
There are no symptoms of difficiency. Everyone can benefit from supplementing with selenium. Populations that may benefit most from the supplementation of selenium include: children, current or recovering alcoholics, arthritics41, women with breast cancer, the elderly, persons with psoriasis42, 43 athletes, persons on diets, vegetarians, and african Americans and Caucasian women living in the southern United States.
Because the infant or adolescent immune system is not as strong as an adults (even when breastfeeding occurs during infancy), the immune system of a young person can be vulnerable to communicable disease and illness. Selenium supplementation is appropriate and safe for children and infants, as selenium is an ingredient in many baby food formulations44,45. In fact, selenium acts as an immune defense agent in both infant, adolescent and adult populations. In adolescents, selenium may prevent gallstones46.
Selenium deficiency has been correlated with immune system weakness47 and cell death48, 49. Immune system weakness often allows pathogens in animals and humans to cause illness.
Keshan disease is a childhood illnesses that results, in part, from a deficiency of selenium50. For growing children and athletes, selenium intake should be of concern as deficiency may result in an increase in protein oxidization51. Children require high levels of protein synthesis for rapid muscular growth. When protein is oxidized by the liver, protein will not reach muscles, and muscular growth and maturation will be stunted. The same holds true for bodybuilders and athletes. Children and adults with severe motor and intellectual disabilities, as well as persons suffering from swallowing dysfunction are often deficient in selenium52, 53.
It has been demonstrated that women with breast cancer are frequently deficient in selenium. Selenium deficiency does not cause cancer, but selenium supplementation will compensate for selenium deficiency in persons with breast cancer54. Newley diagnosed cancer patients should supplement with selenium as they are routinely deficient55.
Selenium has many benefits for elderly persons. Selenium supplementation has been shown to stimulate the production of immune system boosting white blood cells, in elderly populations56.
Bodybuilders and athletes may benefit from selenium supplementation. Many bodybuilders and athletes frequently diet. Persons dieting may become deficient in selenium57. Bodybuilders and athletes on a ketogenic diet may benefit from selenium supplementation, because ketogenic diets are frequently result in vitamin and mineral deficiencies58. Of particular interest to dieting athletes is the fact that selenium deficiency has a negative impact on thyroid function59. To diet successfully, the thyroid must be functioning correctly. It should be noted that using stimulant-based diuretics will not impact blood selenium levels60.
Older athletes can benefit from selenium supplementation61.
As with any restrictive / alternative nutrition regimen, nutritional deficiencies of all varieties may occur. Vegetarians may become selenium deficient as their alternative diets put them at risk for selenium deficiency62.
Southern U.S. African-american and caucasian women of various ages have been found to be deficient in selenium intake. Supplementation will benefit this population63.
4. How much should be taken? Are there any side effects?
Overdosing with selenium can result in renal lesions, loss of fingernails, skin rash, and adverse changes in the nervous system64.
5. Where can I get it?
There are different brand names that manufacture supplemental selenium.
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