Selenium: Benefits, Dosage, Contraindications

Selenium Deficiency
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Selenium deficiencies occur when daily dietary intake is very low, particularly due to geographical reasons (selenium-poor soils). Several studies consider that an intake of 90 µg is necessary to achieve maximum activity of plasma glutathione peroxidase. Moreover, knowing that there are several selenoproteins whose synthesis is regulated differently according to selenium intake, some researchers believe that this intake is not sufficient. Finally, numerous studies demonstrate the benefit of an additional intake to the nutritional intake to reduce cancer risks. The average daily intake level defined by the EFSA is 70 µg per day, and the maximum chronic daily intake is 300 µg per day.

Posologie

Oral route

70 - 300 µg

Adults

Male fertility issues
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Selenium is essential for male fertility and necessary for the biosynthesis of testosterone and spermatogenesis. Indeed, the selenoprotein of sperm nuclei, GSHPx 4 type, is an antioxidant enzyme that protects sperm from oxidative damage and, through its polymerization in mature sperm, has a structural role preserving sperm stability and mobility. The EFSA has also established that selenium contributes to normal spermatogenesis.

Posologie

Oral route

70 - 300 µg

Adults

Thyroid balance
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Selenium is necessary for the synthesis, activation, and metabolism of thyroid hormones. The thyroid gland has a higher concentration of selenium than any other organ in the body. Selenium is an essential component of the enzyme iodothyronine deiodinase which converts thyroxine (T4) to triiodothyronine (T3). In iodine-deficient individuals, a selenium deficiency can exacerbate hypothyroidism. However, administering selenium alone in this situation may further exacerbate hypothyroidism as the conversion of T4 to T3 is increased, while the thyroid lacks iodine to synthesize more T4. Selenium could also potentially prevent alterations in thyroid hormone levels that are sometimes observed in patients after trauma. The EFSA has established that selenium contributes to the normal functioning of the thyroid.

Posologie

Oral route

70 - 300 µg

Adults

Oxidative stress
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At plasma concentrations below 1000 mcg/L, selenium activates glutathione peroxidase (GSH-Px), which reduces oxidative stress by dealing with free radicals and hydrogen peroxide. At concentrations above 2000 mcg/L, selenium paradoxically increases cellular oxidation by promoting the formation of reactive oxygen species (ROS), such as hydroxyl radicals and superoxide. At higher concentrations, selenium also promotes the intracellular formation of nitric oxide, which is converted into toxic nitrous oxide. To reduce the effect of ROS formation, selenium is often administered with other antioxidants, like vitamin E or vitamin C. Preliminary evidence suggests that selenium and vitamin E work synergistically as antioxidants, and may also synergistically inhibit the growth of prostate cancer cells. Selenium may reduce inflammation by decreasing the cellular concentration of reactive oxygen species (ROS). In the case of liver transplantation, ROS are generated when the organ is reperfused with blood after a period of prolonged warm ischemia. Preliminary evidence suggests that the antioxidant action of selenium may decrease liver damage and improve microcirculation. Selenium may act within a defensive mechanism, reducing oxidative stress in peptic ulcers. The EFSA has established that selenium contributes to the protection of cells against oxidative stress.

Posologie

Oral route

70 - 300 µg

Hair beauty
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The EFSA has established that selenium contributes to the maintenance of normal hair and nails.

Posologie

Oral route

70 - 300 µg

Immune boosting
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Selenium enhances immune function by increasing interleukin-2 (IL-2) activity and promoting the normal growth and development of helper T cells. These actions may be important in the treatment of acquired immunodeficiency syndrome (HIV) as selenium deficiency is common in this disease. There is preliminary experimental evidence that selenium inhibits the reverse transcriptase and replication of the human immunodeficiency virus (HIV). However, there is also evidence that selenium can improve subjective feelings of well-being in HIV-infected patients, but it seems not to affect overall outcomes. Selenium deficiency is associated with increased viral shedding in HIV-infected women. The intake of selenium in the diet of these women may reduce AIDS transmission. There is also evidence suggesting that selenium deficiency may increase inflammatory lung damage caused during influenza virus infection. Selenium could also protect patients infected with hepatitis B or C from developing liver cancer. The EFSA has established that selenium contributes to the normal function of the immune system.

Posologie

Oral route

70 - 300 µg

Pregnancy
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A meta-analysis of three clinical trials shows that taking selenium at 60-100 mcg per day for up to 6 months reduces the risk of pre-eclampsia by 72% compared to placebo in pregnant women. Another analysis showed that the risk of pre-eclampsia is higher in pregnant women with low selenium levels.

Posologie

By oral route

70 - 100 µg

Pregnant women

Prostate Cancer
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There is a slight reduction in the risk of prostate cancer in areas with high selenium soil content (indicator of dietary selenium intake) compared to those with low soil selenium content. In clinical trials, there are conflicting results regarding the effect of selenium on prostate cancer risk. In a large-scale clinical trial, taking 200 µg/day of selenium for 4.5 years significantly reduced the relative risk of prostate cancer by 63% compared to placebo. However, this benefit seems to be limited to patients with selenium deficiency. In another large-scale clinical trial, taking selenium at 200 µg/day for an average of 5.5 years did not significantly reduce the risk of prostate cancer compared to placebo in men with normal PSA (Prostate-Specific Antigen) levels.

Posologie

By oral route

70 - 200 µg

4 - years

Men

Synergies

Chronic Lymphocytic Thyroiditis
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Clinical studies have shown that daily intake of 200 µg of selenium in association with levothyroxine considerably reduces thyroid peroxidase antibodies by about 6% to 30% compared to placebo in adults with thyroiditis, after 3 to 12 months of treatment. (Lower doses below 200 µg per day might not be as effective.) However, established clinical research in affected children suggests that taking selenium 50-200 µg per day, also for 3 to 12 months, does not significantly reduce thyroid peroxidase antibodies.

Posologie

By oral route

70 - 200 µg

1 - years

Adults

Emotional Balance
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A low dietary intake of selenium has been associated with a higher incidence of anxiety, depression, and fatigue. Several studies have examined the relationship between higher dietary intake or selenium supplementation and improvement in mood and reduction in anxiety. Some double-blind studies have shown that short-term selenium supplementation (100 mcg/day) resulted in a significant improvement in mood, and a decrease in anxiety, depression, and fatigue.

Posologie

By oral route

100 µg

8 - weeks

Adults

Hypothyroidism
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Low selenium levels or selenium deficiency seem to reduce the conversion of thyroxine (T4) into triiodothyronine (T3). In addition, selenium intake can worsen hypothyroidism in individuals with iodine deficiency because selenium increases the conversion of T4 into T3, but the thyroid gland lacks iodine to synthesize more T4. Individuals deficient in both iodine and selenium should receive supplementation with selenium and iodine simultaneously to avoid worsening hypothyroidism. On the other hand, selenium does not have a significant effect on thyroid function when iodine intake is sufficient. Some clinical research has shown that daily intake of 200 µg of selenium during pregnancy seems to reduce the risk of postpartum thyroid dysfunction by 41% and permanent hypothyroidism by 42% compared to placebo, in euthyroid pregnant women with thyroid peroxidase antibodies (autoantibodies present in inflammatory thyroid disorders).

Posologie

By oral route

70 - 200 µg

Adults

Rheumatoid Arthritis
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The results of clinical studies regarding the effects of selenium on rheumatoid arthritis (RA) are contradictory. Some clinical research suggests that taking selenized yeast, at a rate of 200 µg/day, slightly improves quality of life without changing objective measurements of RA. Other clinical research suggests that taking selenium 200 µg/day for 3 months improves joint swelling, pain, and morning stiffness, and reduces the need for cortisone and non-steroidal anti-inflammatory drugs for symptomatic control in patients with RA.

Posologie

By oral route

70 - 200 µg

3 - months

Adults

Selenized yeast

HIV Infection
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There are conflicting evidences regarding the effect of selenium on HIV. Some clinical evidence shows that taking 200 µg of selenium daily for up to 2 years can slow down the increase of viral load, increase the number of CD4 cells, and reduce the number of hospitalizations in HIV-positive men and women. However, other evidence shows that daily intake of selenium 100-200 µg does not reduce the risk of opportunistic infections or improve CD4 count or viral load in HIV-positive patients, including pregnant women.

Posologie

By oral route

70 - 200 µg

24 - months

Adults

Detoxification
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Besides its role as an antioxidant, selenium participates in the detoxification of xenobiotics and certain heavy metals by forming metal-selenide complexes.

Posologie

By oral route

70 - 300 µg

Adults