Brazil nuts are the best source of
selenium. Yeast, whole grains, and seafood are also good sources. Animal studies have
found that selenium from yeast is better absorbed than selenium in the form of
selenite.1
Selenium has been used in
connection with the following conditions (refer to the individual
health concern for complete information):
Reliable
and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies
suggesting a health benefit or minimal health benefit. For an herb, supported by traditional use but minimal
or no scientific evidence. For a supplement, little scientific support and/or minimal health
benefit.
Who is likely to be deficient?
While most people probably don’t take in enough selenium, gross deficiencies are rare
in Western countries. Soils in some areas are selenium-deficient and people who eat foods
grown primarily on selenium-poor soils are at risk for deficiency. People with AIDS have been reported to be depleted in
selenium.2 Similarly, limited research has reported an association between heart disease and depleted levels of
selenium.3 People who are deficient in selenium have an increased risk of
developing certain types of rheumatoid
arthritis.4
How much is usually taken?
While the Recommended Dietary Allowance for most adults is 55 mcg per day, an adult intake
of 100–200 mcg of selenium per day is recommended by many doctors.
Are there any side effects or interactions?
Selenium is safe at the level people typically supplement (100–200 mcg); however,
taking more than 900 mcg of selenium per day has been reported to cause adverse effects in
some people.5 Selenium toxicity can result in loss of fingernails, skin rash, and
changes in the nervous system. In the presence of
iodine-deficiency-induced goiter, selenium
supplementation has been reported to exacerbate low thyroid function.6 Although
most research suggests that selenium prevents cancer, one study found an increased risk of a
type of skin cancer (squamous cell carcinoma) in people taking selenium
supplements.7 The National Academy of Sciences recommends that selenium intake not
exceed 400 mcg per day, unless the higher intake is monitored by a healthcare
professional.8 In a double-blind study of people who took 200 mcg of selenium per
day for several years to prevent recurrences of skin cancer, the incidence of diabetes was
higher in people who received selenium (9.7%) than in those who received a placebo
(6.5%).9 While this difference was statistically significant, this finding should
be considered preliminary, since the study was not originally designed to test whether
selenium influences the risk of developing diabetes.
Are there any drug
interactions?
Certain medicines may interact with selenium. Refer to drug interactions for a list of those medicines.
References (To view, roll mouse over the "References" heading; to hide, click on the heading)
1. Yoshida M, Fukunaga K, Tsuchita H, Yasumoto K. An evaluation of the
bioavailability of selenium in high-selenium yeast. J Nutr Sci Vitaminol
1999;45:119–28.
2. Dworkin BM. Selenium deficiency in HIV infection and the acquired
immunodeficiency syndrome (AIDS). Chem Biol Iteract 1994;91:181–6.
3. Moore JA, Noiva R, Wells IC. Selenium concentrations in plasma of
patients with arteriographically defined coronary atherosclerosis. Clin Chem
1984;30:1171–3.
4. Knekt P, Heliovaara M, Aho K, et al. Serum selenium, serum
alpha-tocopherol, and the risk of rheumatoid arthritis. Epidemiology
2000;11:402–5.
5. Yang GQ, Zhou RH. Further observations on the human maximum safe
dietary selenium intake in a seleniferous area of China. J Trace Elem Electrolytes Hlth
Dis 1994;8:159–65.
6. Contempre B, Dumont JE, Ngo B, et al. Effects of selenium
supplementation in hypothyroid subjects of an iodine and selenium deficient area: The possible
danger of indiscriminate supplementation of iodine deficient subjects with selenium. J
Clin Endocrinol Metabol 1991;73:213–5.
7. Duffield-Lillico AJ, Slate EH, Reid ME, et al. Selenium
supplementation and secondary prevention of nonmelanoma skin cancer in a randomized trial.
J Natl Cancer Inst 2003;95:1477–81.
8. Panel on Dietary Antioxidants and Related Compounds, Food and
Nutrition Board, Institute of Medicine, National Academy of Sciences. Dietary Reference
Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. National Academy Press,
Washington, D.C., 2000.
9. Stranges S, Marshall JR, Natarajan R, et al. Effects of long-term
selenium supplementation on the incidence of type 2 diabetes: a randomized trial. Ann
Intern Med 2007;147:217–23.
The information presented in Healthnotes is for informational purposes
only. It is based on scientific studies (human, animal, or in vitro), clinical
experience, or traditional usage as cited in each article. The results reported may not
necessarily occur in all individuals. For many of the conditions discussed, treatment with
prescription or over the counter medication is also available. Consult your doctor,
practitioner, and/or pharmacist for any health problem and before using any supplements or
before making any changes in prescribed medications. Information expires June 2009.
Reliable
and relatively consistent scientific data showing a substantial health benefit.
