Selenium supplements have cancer-preventive properties (Combs GF, Jr. 2005), particularly in reducing the occurrence of lung, colorectal, esophageal, and prostate cancers (Mark SD et al 2000). Indeed, low selenium levels are associated with a four- to fivefold increase in the risk of developing prostate cancer (Brooks JD et al 2001). Higher selenium levels are associated with a reduced risk of prostate cancer (Brooks JD et al 2001). Because selenium levels decline with age, selenium supplements may be of particular benefit to elderly men (Brooks JD et al 2001).
However, the benefits of selenium supplements in preventing cancer appear to be cancer-specific, as some clinical studies have shown supplementation to be ineffective in protecting against basal and squamous cell carcinomas of the skin (Clark LC et al 1996).
Clinical studies have shown that vitamin E can reduce the risk of prostate and lung cancers, particularly when used in combination with selenium supplements (Helzlsouer KJ et al 2000; Woodson K et al 1999). Regular and long-term (over 10 years) use of vitamin E reduces the risk of death from bladder cancer (Jacobs EJ et al 2002). Similarly, the use of vitamin E supplements for longer than three years slightly reduces the risk of recurrence among breast cancer survivors (Fleischauer AT et al 2003).
In addition, animal studies indicate that vitamin E may have activity against colon cancer and melanoma (Barnett KT et al 2002; Malafa MP et al 2002b; Malafa MP et al 2002a). Larger clinical studies are currently underway to further assess vitamin E’s protective role against prostate cancer (Fleshner N et al 2005; Lippman SM et al 2005).
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