Until the late 1950s, selenium was thought to be toxic. Although it can indeed be toxic at high doses, it is now recognized as an important nutritional trace mineral. Selenium plays important roles in detoxification and antioxidant defense mechanisms in the body.

Dosage Info

Dosage Range

Doses used safely in clinical trials range from 21 to 200mcg daily for adults. (1) , (2)

Most Common Dosage

100mcg daily

Dosage Forms

Tablets, capsules, and liquid.

Interactions and Depletions


Reported Uses

While selenium is itself an antioxidant, it is also vital for the formation of one of the body’s key antioxidants. This antioxidant activity is believed to be responsible for selenium’s reported ability to protect against heart attacks and strokes while supporting overall cardiovascular health. However, a study involving 153 people with coronary artery disease and low HDL (good) cholesterol questioned these benefits. The antioxidants vitamin C, vitamin E, beta-carotene and selenium were added to cholesterol treatment of simvastatin and niacin and continued to show improvement over placebo, but decreased the benefits seen on HDL cholesterol measurements from simvastatin and niacin without the antioxidants. (3)

Also, studies have linked low dietary selenium intake with higher rates of several types of cancer. (4) , (5) , (6) , (7) , (8) , (9) , (10)

Selenium may also have anti-viral properties by enhancing the body’s cellular defenses. (11) , (12) It may also help rid the body of heavy metal toxins like mercury and cadmium.

Targeted clinical applications for selenium include use in the fight against AIDS, bronchial asthma and cataracts. (13) , (14) , (15)

Toxicities & Precautions


[span class=alert]Be sure to tell your pharmacist, doctor, or other health care providers about any dietary supplements you are taking. There may be a potential for interactions or side effects.[/span]


Large doses of this dietary supplement can cause toxicity. Symptoms include loss of hair and nails, skin lesions, nervous system abnormalities, digestive dysfunction and a garlicky breath odor. (16) It may be necessary to reduce the dose of this dietary supplement. Tell your doctor if these symptoms occur.

Pregnancy / Breast Feeding

To date, the medical literature has not reported any adverse effects related to fetal development during pregnancy or to infants who are breast-fed. Proper nutrition is essential during pregnancy for the healthy development of the fetus. Numerous vitamins and minerals are a vital part of proper nutrition. If you are pregnant, think you might be pregnant, trying to get pregnant, or breast-feeding an infant, talk to your healthcare professional about supplementing your diet with appropriate vitamins and minerals.

Age Limitations

To date, the medical literature has not reported any adverse effects specifically related to the use of this dietary supplement in children. Vitamins and minerals are an essential part of proper growth and development. Talk to your healthcare professional about the appropriate use of vitamins and minerals in children. Do not use any vitamin or mineral in children under 2 years of age unless first discussed with your healthcare professional.


  1. View Abstract: Levander OA. Selenium requirements as discussed in the 1996 joint FAO/IAEA/WHO expert consultation on trace elements in human nutrition. Biomed Environ Sci. Sep1997;10(2-3):214-219.
  2. View Abstract: Clark LC, Combs GF Jr, Turnbull BW, Slate EH, Chalker DK, Chow J, et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial, Nutritional Prevention of Cancer Study Group. JAMA. Dec1996;276(24):1957-1963.
  3. View Abstract: Cheung MC, Zhao XQ, Chait A, Albers JJ, Brown BG. Antioxidant supplements block the response of HDL to simvastatin-niacin therapy in patients with coronary artery disease and low HDL. Arterioscler Thromb Vasc Biol. Aug2001;21(8):1320-6.
  4. View Abstract: Schrauzer GN, et al. Cancer Mortality Correlation Studies–III: Statistical Associations with Dietary Selenium Intakes. Bioinorg Chem. 1977;7(1):23-31.
  5. View Abstract: Combs GF Jr, et al. Reduction of cancer mortality and incidence by selenium supplementation. Med Klin. Sep1997;92(Suppl 3):42-5.
  6. View Abstract: Federico A, et al. Effects of selenium and zinc supplementation on nutritional status in patients with cancer of digestive tract. Eur J Clin Nutr. Apr2001;55(4):293-7.
  7. View Abstract: Wong HK, et al. Effects of selenium supplementation on malignant lymphoproliferative pathologies associated with OF1 mouse ageing. Anticancer Res. Jan2001;21(1A):393-402.
  8. View Abstract: Thikkurissy S, et al. Effect of interleukin-2 and selenium on the growth of squamous cell carcinoma cells. Otolaryngol Head Neck Surg. Feb2001;124(2):142-9.
  9. View Abstract: Combs GF Jr, et al. Chemopreventive agents: selenium. Pharmacol Ther. Sep1998;79(3):179-92.
  10. View Abstract: Combs GF. Status of selenium in prostate cancer prevention. Br J Cancer. 2004 Jun 22 [Epub ahead of print]
  11. View Abstract: Ferencik M, Ebringer L. Modulatory effects of selenium and zinc on the immune system. Folia Microbiol (Praha). 2003;48(3):417-26.
  12. View Abstract: Broome CS, McArdle F, Kyle JA, et al. An increase in selenium intake improves immune function and poliovirus handling in adults with marginal selenium status. Am J Clin Nutr. Jul2004;80(1):154-62.
  13. View Abstract: Schrauzer GN, et al. Selenium in the Maintenance and Therapy of HIV-infected Patients. Chem Biol Interact. Jun1994;91(2-3):199-205.
  14. View Abstract: Kadrabova J, et al. Selenium Status is Decreased in Patients with Intrinsic Asthma. Biol Trace Elem Res. Jun1996;52(3):241-48.
  15. View Abstract: Karakucuk S, et al. Selenium Concentrations in Serum, Lens and Aqueous Humour of Patients with Senile Cataract. Acta Ophthalmol Scand. Aug1995;73(4):329-32.
  16. View Abstract: Holness DL, Taraschuk IG, Nethercott JR. Health status of copper refinery workers with specific reference to selenium exposure. Arch Environ Health. Sep1989;44(5):291-7.