JNCI: 4/2/97 NEW SELENIUM FORMS MAY ALLOW HIGHER DOSING
Study Provides Further Support for Cancer Prevention NEW YORK (April 2, 1997) New synthetic selenium compounds may provide a way to minimize toxicity associated with higher selenium intake, according to a new study in the Journal of the National Cancer Institute. Researchers from the American Health Foundation, in Valhalla, New York evaluated two newly synthesized selenium compounds, p-methoxy-BSC (p-methoxy-benzyl selenocyanate) and p-XSC (1,4-phenylenebis(methylene)selenocyanate). The compounds prevented both precancerous cell growth and tumor growth in the animals after they had received a compound known to induce colorectal cancer.
The effect was seen both in rats receiving a high-fat diet (a known risk factor for colorectal cancer) and a low-fat diet. Perhaps the most significant finding was that the compounds did not induce toxic side effects even when given at doses two-and-a-half times as high as the dose considered safe for elemental selenium. "Observational and experimental studies have suggested that dietary supplementation with selenium can inhibit the development of colon cancer. However, many forms of selenium are toxic," the researchers noted.
A landmark study in JAMA (12/24/96) concluded that selenium supplements may help protect against cancers of the lung, colon and rectum, and prostate. Patients in that study 200 micrograms of the trace element form of selenium per day for a mean of 4.5 years without toxic effects. Those researchers noted that the selenium dose of 200 micrograms per day is within the normal dietary intake of Americans and provides approximately twice the projected typical dietary intake of the study patients.
Researchers are not sure how to explain the apparent anti-carcinogenic properties of selenium. Hypotheses explaining selenium's inhibition of tumor growth include antioxidant properties; the ability to alter carcinogen metabolism; effects on the endocrine and immune systems; and inhibition of protein synthesis. Selenium is an essential nutrient that help metabolize vitamin E and ensure optimal liver function. Disease associated with selenium deficiency are rare in humans but can include heart failure and severe arthritis. Diseases associated with excess selenium intake (usually in areas where there is excessive selenium in the soil) include hair loss, nail deformation, halitosis and flu-like symptoms.
While further studies are needed to determine the safety and efficacy of various selenium compounds in humans, these compounds could someday prove useful in the prevention of cancer, notes Dr. Karam El-Bayoumy, chief of division of cancer etiology and prevention, American Health Foundation. The research is reported in Volume 89: Issue 7: April 2 1997, of the Journal of the National Cancer Institute. Issue 7: April 2 1997