Selenium and its health benefits
What is selenium? What are the health benefits of selenium?

Selenium is a trace mineral essential to good health [1.2]. Selenium asserts its health benefits via the production of
selenoproteins. Selenium is incorporated into proteins to make selenoproteins. Selenoproteins are antioxdants to help
prevent cellular damage from free radicals. Free radicals are natural by-products of oxygen metabolism that may
contribute to the development of chronic diseases such as cancer and heart disease [2,3]. Selenoproteins help regulate
thyroid function and play a role in the immune system [4-7]. Selenium may provide important health benefits to people
whose oxidative stress loads are high, such as those with inflammatory or infectious diseases like rheumatoid arthritis or
human immunodeficiency virus/acquired immunodeficiency syndrome, or who are at high risk for cancers, particularly
prostate cancer. [A2] Therefore, some people consider selenium as a vitamin offering multiple health benefits.

What are the food sources of selenium?
Plant foods are the major food sources of selenium. The content of selenium in food depends on the selenium content of
the soil where plants are grown or animals are raised. For example, soils in northern Nebraska and the Dakotas have
very high levels of selenium. People living in those regions generally have the highest selenium intakes in the United
States (U.S.) [8]. In the U.S., food distribution patterns across the country help prevent people living in low-selenium
geographic areas from having selenium deficiency. Soils in some parts of China and Russia have very low amounts of
selenium. Selenium deficiency is often reported in those regions because most food in those areas is grown and eaten
locally.

Other foods with selenium include some meats and seafood. Animals that eat grains or plants that were grown in
selenium-rich soil have higher levels of selenium in their muscle. In the U.S., meats and bread are common sources of
dietary selenium [9,10] Some nuts are also sources of selenium.

Selenium content of foods can vary. For example, Brazil nuts may contain as much as 544 micrograms of selenium per
ounce. They also may contain far less selenium. It is wise to eat Brazil nuts only occasionally because of their unusually
high intake of selenium. Other common food sources of selenium include tuna, beef, spaghetti, cod, turkey, chicken,
noodles, macaroni, egg, cottage cheese, oatmeal, rice, bread and walnuts.

What is the recommended dosage for selenium?
Recommendations for selenium are provided in the Dietary Reference Intakes developed by the Institute of Medicine [12].
The Recommended Dietary Allowances (RDA) for selenium for healthy adults is 55 ug/day.

When can selenium deficiency occur?
Human selenium deficiency is seen, where soil concentration of selenium is low [15]. There is evidence that selenium
deficiency may contribute to development of a form of heart disease, hypothyroidism, and a weakened immune system
[16,17].

Selenium deficiency can also make the body more susceptible to illnesses caused by other nutritional, biochemical or
infectious stresses [18].

Three specific diseases frequently associated with selenium deficiency are Keshan Disease [enlarged heart and poor
heart function], Kashin-Beck Disease [osteoarthropathy] and Myxedematous Endemic Cretinism [mental retardation].

Keshan disease was first described in the early 1930s in China, and is still seen in large areas of the Chinese
countryside with selenium poor soil [18]. Dietary intake in these areas is less than 19 micrograms per day for men and
less than 13 micrograms per day for women, significantly lower than the current RDA for selenium [12]. Researchers
believe that selenium deficient people infected with a specific virus are most likely to develop Keshan disease [18,19].

Selenium deficiency has also been seen in people who rely on total parenteral nutrition (TPN) as their sole source of
nutrition [20,21]. TPN is a method of feeding nutrients through an intravenous (IV) line to people whose digestive systems
do not function. Forms of nutrients that do not require digestion are dissolved in liquid and infused through the IV line. It is
important for TPN solutions to provide selenium in order to prevent a deficiency [22]. Physicians can monitor the selenium
status of individuals receiving TPN to make sure they are receiving adequate amounts.

Severe gastrointestinal disorders may decrease the absorption of selenium, resulting in selenium depletion or deficiency
[23]. Gastrointestinal problems that impair selenium absorption usually affect absorption of other nutrients as well, and
require routine monitoring of nutritional status so that appropriate medical and nutritional treatment can be provided.

Who may need supplemental selenium?
In the U.S., most cases of selenium depletion or deficiency are associated with severe gastrointestinal problems, such as
Crohn's disease, or with surgical removal of part of the stomach. These and other gastrointestinal disorders can impair
selenium absorption [24-26]. People with acute severe illness who develop inflammation and widespread infection often
have decreased levels of selenium in their blood [27]. Physicians will evaluate individuals who have gastrointestinal
disease or severe infection for depleted blood levels of selenium to determine the need for supplementation.

People with iodine deficiency may also benefit from selenium supplementation. Iodine deficiency is rare in the U.S., but is
still common in developing countries where access to iodine is limited [28]. Researchers believe that selenium deficiency
may worsen the effects of iodine deficiency on thyroid function, and that adequate selenium nutritional status may help
protect against some of the neurological effects of iodine deficiency [6,7]. Researchers involved in the Supplementation en
Vitamines et Mineraux AntioXydants (SU.VI.MAX) study in France, which was designed to assess the effect of vitamin and
mineral supplements on chronic disease risk, evaluated the relationship between goiter and selenium in a subset of this
research population. Their findings suggest that selenium supplements may be protective against goiter, which refers to
enlargement of the thyroid gland [29].

As noted above, selenium supplementation during TPN administration is now routine [21,22]. While specific medical
problems such as those described above indicate a need for selenium supplementation, evidence is lacking for
recommending selenium supplements for healthy children and adults.

Selenium supplements
Selenium occurs in staple foods such as corn, wheat, and soybean as selenomethionine, the organic selenium analogue
of the amino acid methionine [30,31]. Selenomethionine can be incorporated into body proteins in place of methionine,
and serves as a vehicle for selenium storage in organs and tissues. Selenium supplements may also contain sodium
selenite and sodium selenate, two inorganic forms of selenium. Selenomethionine is generally considered to be the best
absorbed and utilized form of selenium.

Selenium is also available in 'high selenium yeasts', which may contain as much as
1,000 to 2,000 micrograms of
selenium per gram [30]. Most of the selenium in these yeasts is in the form of selenomethionine. This form of selenium
was used in the large scale cancer prevention trial in 1983, which demonstrated that taking a daily supplement [dosage:
200 micrograms of selenium per day] could lower the risk of developing prostate, lung, and colorectal cancer [32].
However, some yeasts may contain inorganic forms of selenium, which are not utilized as well as selenomethionine.

A study conducted in 1995 suggested that the organic forms of selenium increased blood selenium concentration to a
greater extent than inorganic forms. However, it did not significantly improve the activity of the selenium-dependent
enzyme, glutathione peroxidase [33].

Selenium and Cancer
Observational studies indicate that death from cancer, including lung, colorectal, and prostate cancers, is lower among
people with higher blood levels or intake of selenium [34-40]. In addition, the incidence of nonmelanoma skin cancer is
significantly higher in areas of the United States with low soil selenium content [37]. The effect of selenium
supplementation on the recurrence of different types of skin cancers was studied in seven dermatology clinics in the U.S.
from 1983 through the early 1990s. Taking a daily supplement with dosage of 200 ug of selenium did not affect recurrence
of skin cancer, but significantly reduced the occurrence and death from total cancers. The incidence of prostate cancer,
colorectal cancer, and lung cancer was notably lower in the group given selenium supplements [41].

Research suggests that selenium affects cancer risk in two ways. As an anti-oxidant, selenium can help protect the body
from damaging effects of free radicals. Selenium may also prevent or slow tumor growth. Certain breakdown products of
selenium are believed to prevent tumor growth by enhancing immune cell activity and suppressing development of blood
vessels to the tumor [42].

Rayman MP from University of Surrey, Guildford, UK, suggested that selenium is an unusual trace element in having its
own codon in mRNA that specifies its insertion into selenoproteins as selenocysteine (SeCys), by means of a
mechanism requiring a large SeCys-insertion complex. This exacting insertion machinery for selenoprotein production
has implications for the selenium requirements for cancer prevention. If selenium may protect against cancer, an
adequate intake of selenium is desirable. [A1]

However, not all studies have shown a relationship between selenium status and cancer. In 1982, over 60,000
participants of the Nurse's Health Study with no history of cancer submitted toenail clippings for selenium analysis.
Toenails are thought to reflect selenium status over the previous year. After three and a half years of data collection,
researchers compared toenail selenium levels of nurses with and without cancer. Those nurses with higher levels of
selenium in their toenails did not have a reduced risk of cancer [43]. Current primary and secondary prevention trials of
selenium are underway in the USA, including the Selenium and Vitamin E Cancer Prevention Trial (SELECT) relating to
prostate cancer, [A1]

Selenium and heart disease
Some population surveys have suggested an association between lower antioxidant intake and a greater incidence of
heart disease [46]. Evidence also suggests that oxidative stress from free radicals, which are natural by-products of
oxygen metabolism, may promote heart disease [47-49]. For example, it is the oxidized form of low-density lipoproteins
(LDL, often called "bad" cholesterol) that promotes plaque build-up in coronary arteries [48]. Selenium is one of a group of
antioxidants that may help limit the oxidation of LDL cholesterol and thereby help to prevent coronary artery disease
[47-49]..

Selenium and arthritis
Surveys indicate that individuals with rheumatoid arthritis, a chronic disease that causes pain, stiffness, swelling, and
loss of function in joints, have reduced selenium levels in their blood [50-51]. In addition, some individuals with arthritis
have a low selenium intake [52].

The body's immune system naturally makes free radicals that can help destroy invading organisms and damaged tissue,
but that can also harm healthy tissue [53]. Selenium, as an antioxidant, may help to relieve symptoms of arthritis by
controlling levels of free radicals [54].

Selenium and HIV
HIV/AIDS malabsorption can deplete levels of many nutrients, including selenium. Selenium deficiency is associated with
decreased immune cell counts, increased disease progression, and high risk of death in the HIV/AIDS population [55,56].
HIV/AIDS gradually destroys the immune system, and oxidative stress may contribute to further damage of immune cells.
Antioxidant nutrients such as selenium help protect cells from oxidative stress, thus potentially slowing progression of the
disease [57]. Selenium also may be needed for the replication of the HIV virus, which could further deplete levels of
selenium [58].

An examination of 125 HIV-positive men and women linked selenium deficiency with a higher rate of death from HIV [59].
In a small study of 24 children with HIV who were observed for five years, those with low selenium levels died at a younger
age, which may indicate faster disease progression [60]. Results of research studies have led experts to suggest that
selenium status may be a significant predictor of survival for those infected with HIV [61].

What are the side effects of selenium? Is high dose of selenium poisoning?
Within the recommended daily allowance, selenium appears to be safe. However, high blood levels of selenium (greater
than 100 ug/dL) can lead to a side effect called selenosis [62]. Symptoms of selenosis include gastrointestinal upsets,
hair loss, white blotchy nails, garlic breath odor, fatigue, irritability, and mild nerve damage [2].
Selenium toxicity is rare. The few reported cases have been associated with industrial accidents and a manufacturing
error that led to an excessively high dose of selenium in a supplement [63,64]. The Institute of Medicine of the National
Academy of Sciences has set a tolerable upper intake level (UL) for selenium at
400 micrograms per day for adults to
prevent the risk of developing the side effect, i.e. selenosis [12].
the relationship was established. Am J Clin Nutr 1993;57 (2 Suppl):244S-8S. 8 Longnecker MP, Taylor PR, Levander OA, Howe M, Veillon C, McAdam PA, Patterson KY, Holden JM, Stampfer
MJ, Morris JS, Willett WC. Selenium in diet, blood, and toenails in relation to human health in a seleniferous area. Am J Clin Nutr 1991;53:1288-94. 9 Pennington JA and Schoen SA.
Contributions of food groups to estimated intakes of nutritional elements: Results from the FDA total diet studies, 1982-91. Int J Vitam Nutr Res 1996;66:342-9. 10 Pennington JA and
Young BE. Total diet study nutritional elements. J Am Diet Assoc 1991;91:179-83. 11 U.S. Department of Agriculture, Agricultural Research Service. 2003. USDA National Nutrient Database
for Standard Reference, Release 16. Nutrient Data Laboratory Home Page 12 Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: Vitamin C, Vitamin E, Selenium,
and Carotenoids. National Academy Press, Washington, DC, 2000. 13 Bialostosky K, Wright JD, Kennedy-Stephenson J, McDowell M, Johnson CL. Dietary intake of macronutrients,
micronutrients and other dietary constituents: United States 1988-94. Vital Heath Stat. 11(245) ed: National Center for Health Statistics, 2002. 14 Zhou BF, Stamler J, Dennis B,
Moag-Stahlberg A, Okuda N, Robertson C, Zhao L, Chan Q, Elliott P for the INTERMAP Research Group. Nutrient intakes of middle-aged men and women in China, Japan, United Kingdom,
and United States in the alte 1990s: The INTERMAP Study. J of Human Hypertension. 2003;17:623-30. 15 Ellis DR and Salt DE. Plants, selenium and human health. Curr Opin Plant Biol
2003;6:273-9. 16 Combs GF. Food system-based approaches to improving micronutrient nutrition: the case for selenium. Biofactors 2000;12:39-43. 17 Zimmerman MB and Kohrle J. The
impact of iron and selenium deficiencies on iodine and thyroid metabolism: biochemistry and relevance to public health. Thyroid 2002;12:867-78. 18 Beck MA, Levander O, Handy J.
Selenium deficiency and viral infection. J of Nutr 2003;133:1463S-67S. 19 Levander OA and Beck MA. Interacting nutritional and infectious etiologies of Keshan disease. Insights from
coxsackie virus B-induced myocarditis in mice deficient in selenium or vitamin E. Biol Trace Elem Res 1997;56:5-21. 20 Levander OA. Scientific rationale for the 1989 recommended
dietary allowance for selenium. J Am Diet Assoc 1991;91:1572-6. 21 Gramm HJ, Kopf A, Bratter P. The necessity of selenium substitution in total parenteral nutrition and artificial
alimentation. J Trace Elem Med Biol 1995;9:1-12. 22 Abrams CK, Siram SM, Galsim C, Johnson-Hamilton H, Munford FL, Mezghebe H. Selenium deficiency in long-term total parenteral
nutrition. Nutr Clin Pract 1992;7:175-8. 23 Rannem T, Ladefoged K, Hylander E, Hegnhoj J, Staun M. Selenium depletion in patients with gastrointestinal diseases: Are there any predictive
factors? Scand J Gastroenterol 1998;33:1057-61. 24 Kuroki F, Matsumoto T, Lida M. Selenium is depleted in Crohn's disease on enteral nutrition. Digestive Diseases 2003;21:266-70. 25
Rannem T, Ladefoged K, Hylander E, Hegnhoj J, Jarnum S. Selenium status in patients with Crohn's disease. Am J Clin Nutr 1992;56:933-7. 26 Bjerre B, von Schenck H, Sorbo B.
Hyposelaemia: Patients with gastrointestinal diseases are at risk. J Intern Med 1989;225:85-8. 27 Gartner R, Albrich W, Angstwurm MW. The effect of a selenium supplementation on the
outcome of patients with severe systemic inflammation, burn, and trauma. BioFactors 14 2001; 199-204. 28 Berdanier, CD. Advanced Nutrition: Micronutrients. CRC Press 1998; 208-11.
29 Derumeaux H, Valeix P, Castetbon K, Bensimon M, Boutron-Ruault MC, Arnaud J, Hercberg S. Association of selenium with thyroid volume and echostructure in 35- to 60-year-old
French adults. Eur J Endocrinol 2003;148(3):309-15. 30 Schrauzer GN. Commentary: Nutrition selenium supplements: Product types, quality, and safety. J Am College of Nutr 2001;20:1-4.
31 Schrauzer GN. The nutritional significance, metabolism and toxicology of selenomethionine. Adv Food Nutr Res 2003:47:73-112. 32 Clark LC, Combs Jr GF, Turnbull BW, Slate EH,
Chalker D, Chow J, Davis LS, Glover RA, Graham GF, Gross EG, Krongrad A, Lesher JL, Park HK, Sanders BB, Smith CL, Taylor JR. Effects of selenium supplementation for cancer
prevention in patients with carcinoma of the skin. A randomized controlled trial. J Am Med Assoc 1996;276:1957-63. 33 Neve J. Human selenium supplementation as assessed by changes
in blood selenium concentration and glutathione peroxidase activity. J Trace Elem Med Biol 1995;9:65-73. 34 Russo MW, Murray SC, Wurzelmann JI, Woosley JT, Sandler RS. Plasma
selenium levels and the risk of colorectal adenomas. Nutr Cancer 1997;28:125-9. 35 Patterson BH and Levander OA. Naturally occurring selenium compounds in cancer chemoprevention
trials: A workshop summary. Cancer Epidemiol Biomarkers Prev 1997;6:63-9. 36 Knekt P, Marniemi J, Teppo L, Heliovaara M, Aromaa A. Is low selenium status a risk factor for lung
cancer? Am J Epidemiol 1998;148:975-82. 37 Fleet JC. Dietary selenium repletion may reduce cancer incidence in people at high risk who live in areas with low soil selenium. Nutr Rev
1997;55:277-9. 38 Shamberger RJ. The genotoxicity of selenium. Mutat Res 1985;154:29-48. 39 Young KL and Lee PN. Intervention studies on cancer. Eur J Cancer Prev 1999;8:91-103. 40
Burguera JL, Burguera M, Gallignani M, Alarcon OM, Burgueera JA. Blood serum selenium in the province of Merida, Venezuela, related to sex, cancer incidence and soil selenium content.
J Trace Elem Electrolytes Health Dis 1990;4:73-7. 41 Combs GF, Jr., Clark LC, Turnbull BW. Reduction of cancer risk with an oral supplement of selenium. Biomed Environ Sci
1997;10:227-34. 42 Combs GF, Clark LC, Turnbull BW. An analysis of cancer prevention by selenium. BioFactors 14 2001; 153-9. 43 Garland M, Morris JS, Stampfer MJ, Colditz GA, Spate
VL, Baskett CK, Rosner B, Speier FE, Willett WC, Hunter DJ. Prospective study of toenail selenium levels and cancer among women. J Natl Cancer Inst 1995;87:497- 505. 44 Hercberg S,
Galan P, Preziosi P, Roussel AM, Arnaud J, Richard MJ, Malvy D, Paul-Dauphin A, Briancon S, Favier A. Background and rationale behind the SU.VI.MAX Study, a prevention trial using
nutritional doses of a combination of antioxidant vitamins and minerals to reduce cardiovascular diseases and cancers. Supplementation en VItamines et Mineraux AntiXydants Study. Int
J Vitam Nutr Res 1998;68:3-20. 45 Klein EA, Thompson IM, Lippman SM, Goodman PJ, Albanes D, Taylor PR, Coltman C. SELECT: the next prostate cancer prevention trial. Selenium and
Vitamin E Cancer Prevention Trial. Journal of Urology 2001;166(4):1311-5. 46 Gey KF. Vitamins E plus C and interacting conutrients required for optimal health. A critical and constructive
review of epidemiology and supplementation data regarding cardiovascular disease and cancer. Biofactors 1998;7:113-74. 47 Ozer NK, Boscoboinik D, Azzi A. New roles of low density
lipoproteins and vitamin E in the pathogenesis of atherosclerosis. Biochem Mol Biol Int 1995;35:117-24. 48 Lapenna D, de Gioia S, Ciofani G, Mezzetti A, Ucchino S, Calafiore AM,
Napolitano AM, Di Ilio C, Cuccurulo F. Glutathione-related antioxidant defenses in human atherosclerotic plaques. Circulation 1998;97:1930-4. 49 Neve J. Selenium as a risk factor for
cardiovascular diseases. J Cardiovasc Risk 1996;3:42-7. 50 Kose K, Dogan P, Kardas Y, Saraymen R. Plasma selenium levels in rheumatoid arthritis. Biol Trace Elem Res 1996;53:51-6. 51
Heliovaara M, Knekt P, Aho K, Aaran RK, Alfthan G, Aromaa A. Serum antioxidants and risk of rheumatoid arthritis. Ann Rheum Dis 1994;53:51-3. 52 Stone J, Doube A, Dudson D, Wallace
J. Inadequate calcium, folic acid, vitamin E, zinc, and selenium intake in rheumatoid arthritis patients: Results of a dietary survey. Semin Arthritis Rheum 1997;27:180-5. 53 Grimble RF.
Nutritional antioxidants and the modulation of inflammation: Theory and practice. New Horizons 1994;2:175-85. 54 Aaseth J, Haugen M, Forre O. Rheumatoid arthritis and metal
compounds- perspectives on the role of oxygen radical detoxification. Analyst 1998;123:3- 6. 55 Look MP, Rockstroh JK, Rao GS, Kreuzer KA, Spengler U, Sauerbruch T. Serum selenium
versus lymphocyte subsets and markers of disease progression and inflammatory response in human immunodeficiency virus-1 infection. Biol Trace Elem Res 1997;56(1):31-41. 56
Singhal N and Austin J. A clinical review of micronutrients in HIV infection. J Int Assoc Physicians AIDS Care 2002;1:63-75. 57 Romero-Alvira D and Roche E. The keys of oxidative stress
in acquired immune deficiency syndrome apoptosis. Medical Hypotheses 1998;51(2):169-73. 58 Patrick L. Nutrients and HIV; Part One - Beta carotene and selenium. Altern Med Rev
1999;4:403-13. 59 Baum MK, Shor-Posner G, Lai S, Zhang G, Lai H, Fletcher MA, Sauberlich H, Page JB. High risk of HIV-related mortality is associated with selenium deficiency. J Acquir
Immune Defic Syndr Hum Retrovirol 1997;15:370-4. 60 Campa A, Shor-Posner G, Indacoche F, Zhang G, Lai H, Asthana D, Scott GB, Baum MK. Mortality risk in selenium-deficient
HIV-positive children. J Acquir Immune Defic Syndr Hum Retrovirol 1999;15:508-13. 61 Baum MK and Shor-Posner G. Micronutrient status in relationship to mortality in HIV-1 disease.
Nutr Rev 1998;56:S135-9. 62 Koller LD and Exon JH. The two faces of selenium-deficiency and toxicity are similar in animals and man. Can J Vet Res 1986;50:297-306. 63 Hathcock J.
Vitamins and minerals: Efficacy and safety. Am J Clin Nutr 1997;66:427-37. 64 Raisbeck MF, Dahl ER, Sanchez DA, Belden EL, O'Toole D. Naturally occurring selenosis in Wyoming. J Vet
Diagn Invest 1993;5:84-7. 65 Dietary Guidelines Advisory Committee, Agricultural Research Service, United States Department of Agriculture (USDA). HG Bulletin No. 232, 2000. 66 Center
for Nutrition Policy and Promotion, United Stated Department of Agriculture. Food Guide Pyramid, 1992 (slightly revised 1996). [A1] Selenium in cancer prevention: a review of the
evidence and mechanism of action. Proc Nutr Soc. 2005 Nov;64(4):527-42. [A2] Ryan-Harshman M and Aldoori W The relevance of selenium to immunity, cancer, and
infectious/inflammatory diseases. Can J Diet Pract Res. 2005 Summer;66(2):98-102.
Source Dietary Supplement Fact Sheet: Selenium, U.S. Department of Health and Human Services, Online Publication January 2006.         


Walnut is a good source of selenium.         



Selenium may benefit people at cancer risk; some research suggested.         
The National Cancer Institute has
halted its $114 million study of
whether vitamin E and selenium
can prevent prostate cancer.

Earlier smaller studies had
suggested the nutrients might
help, but instead they've become
the latest failures in a quest to find
cancer-preventing dietary
supplements.  These two
supplements were believed to
help prevent prostate cancer. Both
are antioxidants -- compounds
that interfere with chemical
reactions that can damage cells
and DNA.

data showed no benefit for the
data showed no benefit for the
treatment. In the study, the men
received either vitamin E (400
milligrams) and
selenium (200
micrograms)
, , vitamin E and
placebo, vitamin E and placebo,
selenium and placebo, or
placebos alone.
placebos alone.
THIS WEBSITE TALKS ABOUT THE SIDE EFFECTS AND THE POTENTIAL HEALTH BENEFITS OF HERBS, SUPPLEMENTS,
PHYTONUTRIENTS AND DRUG PRODUCTS. THIS WEBSITE ALSO TALKS ABOUT SOME POPULAR HEALTH ISSUES AND DISEASES.
ARTICLES IN THIS WEB SITE IS FOR YOUR REFERENCE ONLY. IF YOU HAVE ANY QUESTION, YOU SHOULD CONSULT WITH YOUR
DOCTOR IMMEDIATELY. ALL RIGHTS RESERVED 2011. DO NOT COPY NOR TRANSFER ARTICLES TO OTHER WEBSITES NOR OTHER
FORMS OF PUBLICATIONS.
Privacy Policy. ARTICLE INDEX