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.1 2 3 4 5 6 7

In addition, the incidence of non melanoma skin cancer is significantly higher in areas of the United States with low soil selenium content.8

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 containing 200 μg 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.9

Research suggests that selenium affects cancer risk in two ways. As an antioxidant, 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.10

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.11

Two long-term studies, the SU.VI.MAX study in France and the Selenium and Vitamin E Cancer Prevention Trial (SELECT) in the United States and Canada, investigated whether selenium combined with at least one other dietary supplement could reduce the risk of prostate cancer in men.

The SU.VI.MAX study examined the effects of a supplement package containing moderate doses of vitamins E and C, beta-carotene, zinc, and selenium (100 μg/day) versus placebo on the risk of chronic diseases such as cancer and cardiovascular disease. Among the 5,141 men enrolled, those randomized to the supplements who began the study with a normal (<3 ng/ml) PSA (prostate specific antigen) level at baseline had their risk of prostate cancer reduced by half.12 Among the men whose PSA levels were elevated at baseline, however, use of the supplements was associated with an increased incidence of prostate cancer of borderline statistical significance compared to placebo.

The Selenium and Vitamin E Cancer Prevention Trial (SELECT) was a very large randomized clinical trial begun in 2001 specifically designed to determine whether 7-12 years of daily supplementation with selenium (200 μg), with or without synthetic vitamin E (400 IU), reduces the number of new prostate cancers in healthy men (PSA ≤4 ng/ml at baseline).13 14. The trial, which had enrolled >35,000 men, was discontinued in October 2008 when an analysis found that the supplements, taken alone or together for an average of 5.5 years, did not prevent prostate cancer. Study staff members will continue to monitor participants' health for an additional 3 years.

Some population surveys have suggested an association between lower antioxidant intake and a greater incidence of heart disease.15 Evidence also suggests that oxidative stress from free radicals, which are natural by-products of oxygen metabolism, may promote heart disease.16 17 18 For example, it is the oxidized form of low-density lipoproteins (LDL, often called "bad" cholesterol) that promotes plaque build-up in coronary arteries.19 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.20 21 22 Currently there is insufficient evidence available to recommend selenium supplements for the prevention of coronary heart disease.

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.23 24 In addition, some individuals with arthritis have a low selenium intake.25

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.26 Selenium, as an antioxidant, may help to relieve symptoms of arthritis by controlling levels of free radicals.27 Current findings are considered preliminary, and further research is needed before selenium supplements can be recommended for individuals with arthritis.

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. ((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.)) Singhal N and Austin J. A clinical review of micronutrients in HIV infection. J Int Assoc Physicians AIDS Care 2002;1:63-75.)) 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.28 Selenium also may be needed for the replication of the HIV virus, which could further deplete levels of selenium.29

An examination of 125 HIV-positive men and women linked selenium deficiency with a higher rate of death from HIV.30 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.31 Results of research studies have led experts to suggest that selenium status may be a significant predictor of survival for those infected with HIV.32

Researchers continue to investigate the relationship between selenium and HIV/AIDS, including the effect of selenium levels on disease progression and mortality. There is insufficient evidence to routinely recommend selenium supplements for individuals with HIV/AIDS, but physicians may prescribe such supplements as part of an overall treatment plan. It is also important for HIV-positive individuals to consume recommended amounts of selenium in their diet.

Related Links: What is selenium? | What foods provide selenium? | How much selenium do I need? | What happens if I do not get enough selenium? | Do I need extra selenium? | Can selenium be harmful? | What are some of the current issues and controversies about selenium? |

Disclaimer
Reasonable care has been taken in preparing this document and the information provided herein is believed to be accurate. However, this information is not intended to constitute an "authoritative statement" under Food and Drug Administration rules and regulations.

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The mission of the Office of Dietary Supplements (ODS) is to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, stimulating and supporting research, disseminating research results, and educating the public to foster an enhanced quality of life and health for the U.S. population.

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The information is not intended to be a substitute for professional medical advice. It is important to seek the advice of a physician about any medical condition or symptom. It is also important to seek the advice of a physician, registered dietitian, pharmacist, or other qualified health professional about the appropriateness of taking dietary supplements and their potential interactions with medications.

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Footnotes

  1. 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. PubMed abstract [↩]
  2. Patterson BH and Levander OA. Naturally occurring selenium compounds in cancer chemoprevention trials: A workshop summary. Cancer Epidemiol Biomarkers Prev 1997;6:63-9. PubMed abstract [↩]
  3. 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. PubMed abstract [↩]
  4. 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. PubMed abstract [↩]
  5. Shamberger RJ. The genotoxicity of selenium. Mutat Res 1985;154:29-48. PubMed abstract [↩]
  6. Young KL and Lee PN. Intervention studies on cancer. Eur J Cancer Prev 1999;8:91-103. PubMed abstract [↩]
  7. 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. PubMed abstract [↩]
  8. 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. PubMed abstract [↩]
  9. Combs GF, Jr., Clark LC, Turnbull BW. Reduction of cancer risk with an oral supplement of selenium. Biomed Environ Sci 1997;10:227-34. PubMed abstract [↩]
  10. Combs GF, Clark LC, Turnbull BW. An analysis of cancer prevention by selenium. BioFactors 14 2001; 153-9. [↩]
  11. 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. PubMed abstract [↩]
  12. Meyer F, Galan P, Douville P, Bairati I, Kegle P, Bertrais S, et al. Antioxidant vitamin and mineral supplementation in the SU.VI.MAX trial. Int J Cancer 2005;116:182-186. [↩]
  13. Lippman SM, Klein EA, Goodman PJ, Lucia MS, Thompson IM, Ford LG, et al. The effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA 2009;301:39-51. [↩]
  14. National Cancer Institute. Questions and Answers: Selenium and Vitamin E Cancer Prevention Trial (SELECT). http://www.cancer.gov/newscenter/pressreleases/SELECTQandA. [↩]
  15. National Cancer Institute. Questions and Answers: Selenium and Vitamin E Cancer Prevention Trial (SELECT). http://www.cancer.gov/newscenter/pressreleases/SELECTQandA. [↩]
  16. 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. PubMed abstract [↩]
  17. 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. PubMed abstract [↩]
  18. Neve J. Selenium as a risk factor for cardiovascular diseases. J Cardiovasc Risk 1996;3:42-7. PubMed abstract [↩]
  19. 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. PubMed abstract [↩]
  20. 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. PubMed abstract [↩]
  21. 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. PubMed abstract [↩]
  22. Neve J. Selenium as a risk factor for cardiovascular diseases. J Cardiovasc Risk 1996;3:42-7. PubMed abstract [↩]
  23. Kose K, Dogan P, Kardas Y, Saraymen R. Plasma selenium levels in rheumatoid arthritis. Biol Trace Elem Res 1996;53:51-6. PubMed abstract [↩]
  24. 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. PubMed abstract [↩]
  25. 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. [PubMed abstract [↩]
  26. Grimble RF. Nutritional antioxidants and the modulation of inflammation: Theory and practice. New Horizons 1994;2:175-85. PubMed abstract [↩]
  27. Aaseth J, Haugen M, Forre O. Rheumatoid arthritis and metal compounds- perspectives on the role of oxygen radical detoxification. Analyst 1998;123:3- 6. >PubMed abstract [↩]
  28. Romero-Alvira D and Roche E. The keys of oxidative stress in acquired immune deficiency syndrome apoptosis. Medical Hypotheses 1998;51(2):169-73. [↩]
  29. Patrick L. Nutrients and HIV; Part One - Beta carotene and selenium. Altern Med Rev 1999;4:403-13. PubMed abstract [↩]
  30. 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. PubMed abstract [↩]
  31. 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. PubMed abstract [↩]
  32. Baum MK and Shor-Posner G. Micronutrient status in relationship to mortality in HIV-1 disease. Nutr Rev 1998;56:S135-9. PubMed abstract [↩]

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