CAM: Selenium

Often ingested as:
Selenomethionine

Structure of Selenomethionine

Intro and Background
Selenium is a component of the amino acid selenomethionine commonly found in soil, forages, and grains. ⁽¹⁾  This naturally occurring amino acid is essential for proper nutrition and in a normal human diet and is most often ingested in meats, seafood, and plants. ^{(2) (3)}  The amount of selenium in plants, animals, and humans depends on the selenium concentration of the soil where they were raised. Investigators started to look at selenium as an anticancer agent when a report suggested that the average selenium intake was lower among nations that showed an increased risk for cancer. ⁽⁴⁾

Please read our notice on CAM and chemoprevention methods

In many studies, selenium is also paired with Vitamin E to investigate their combined cancer fighting abilities. For the most part, research is focused on the ability of selenium to prevent cancer rather than fight it. The exact mechanism by which it works is unknown but it may fight cancer causing events in several different ways: it enhances processes that normally fight cancerous cells ⁽⁵⁾ and prevents harmful molecules from binding to and changing DNA.⁽⁶⁾  The US Food and Drug administration suggests a daily intake of about 70 µg (with a maximum of 400µg/day) for adults as part of a normal, healthy diet.^{(7) (3)}

Scientific Research
Selenium may be an effective agent to prevent cancer but it is not yet clear.^{(8) (9)}  Some studies suggest that a baseline, or minimum, level of selenium intake provides protection from cancer development.^{(10) (3)}  Studies also show that men are at a reduced risk for prostate cancer when selenium is part of their diet. ⁽⁷⁾ Treatment of prostate cancer cells with selenium in vitro can inhibit tumor growth and induce apoptosis. ^{(1) (11)}

There are some indications (included in review by Micke, et. al.) that selenium may increase risk for type II diabetes. ⁽¹⁰⁾

There are currently several clinical trials underway examining selenium's ability to prevent and/or treat cancer.  Studies are underway  to look at the impact on solid tumors and lymphoma View information about ongoing clinical trials involving selenium (National Cancer Institute).

US Food and Drug Administration Approval
There is not enough evidence to support that selenim is effective in the treatment of cancer and it has not been approved by the FDA for cancer treatment. ⁽¹²⁾

1. Menter DG, Sabichi AL, Lippman SM. Selenium effects on prostate cell growth. Cancer Epidemiol Biomarkers Prev. (2000) 11: 1171-82 [PUBMED]
2. Hu H, Jiang C, Ip C, Rustum YM, Lu J. Methylseleninic acid potentiates apoptosis induced by chemotherapeutic drugs in androgen-independent prostate cancer cells. Clinical Cancer Research (2005). 11: 2379-2388. [PUBMED]
3. USDA. Dietary Reference Intakes: Elements National Academy of Sciences. Institute of Medicine. Food and Nutrition Board. Accessed 2 June 2010. [ http://fnic.nal.usda.gov/nal_display/index.php?info_center=4&tax_level=3&tax_subject=256&topic_id=1342&level3_id=5140 ]
4. Rayman MP. Selenium in cancer prevention: a review of the evidence and mechanism of action. Proc Nutr Soc. (2005) 64(4): 527-42 [PUBMED]
5. Zhao H, Brooks JD. Selenomethionine induced transcriptional programs in human prostate cancer cells. J Urol. (2007) 177(2): 743-50 [PUBMED]
6. Whanger PD. Selenium and its relationship to cancer: an update dagger. British Journal of Nutrition (2004). 91: 11-28. [PUBMED]
7. Duffield-Lillico AJ, Dalkin BL, Reid ME, et al. Selenium supplementation, baseline plasma selenium status and incidence of prostate cancer: an analysis of the complete treatment period of the Nutritional Prevention of Cancer Trial. BJU Int. (2003) 91(7): 608-12. [PUBMED]
8. A.J. Duffield-Lillico, B.L. Dalkin, M.E. Reid, B.W. Turnbull, E.H. Slate and E.T. Jacobs et al. Selenium supplementation, baseline plasma selenium status and incidence of prostate cancer: an analysis of the complete treatment period of the Nutritional Prevention of Cancer Trial. British Journal of Urology International. (2003) 91: 608. [PUBMED]
9. Clark LC, Dalkin B, Krongrad A et al. Decreased incidence of prostate cancer with selenium supplementation: results of a double-blind cancer prevention trial. British Journal of Urology 1998; 81: 730-734 [PUBMED]
10. Micke O, Schomburg L, Buentzel J, Kisters K, Muecke R. Selenium in oncology: from chemistry to clinics. Molecules. 2009 Oct 12;14(10):3975-88. [PUBMED]
11. Zu K, Ip C. Synergy between selenium and vitamin E in apoptosis induction is associated with activation of distinctive initiator caspases in human prostate cancer cells. Cancer Research. (2003) 63(20): 6988-95 [PUBMED]
12. US Food and Drug Adminstration website. Accessed 9/10/2010 [http://www.fda.gov/]