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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Selenium's Surprising Anticancer Power
24 December 1996 6:00 pm
In a stunning finding, daily supplements of the trace element selenium have been found to reduce the risk of several types of cancer in patients with a history of skin cancer. The results, reported in tomorrow's issue of the Journal of the American Medical Association, surprised researchers, who are discouraging people from loading up on the supplement until the results are reproduced in other people.
A team led by epidemiologist Larry Clark of the Arizona Cancer Center in Tucson had observed lower rates of skin cancer among people with high levels of selenium. So the group set out to test whether selenium might reduce the chance of recurrence of basal cell or squamous cell carcinoma in people previously treated for skin cancer. Beginning in 1983, they began to enroll patients from seven dermatology clinics in the eastern United States, giving half the group a daily placebo and the other half 200 micrograms of selenium in a brewer's yeast tablet. A total of 1312 patients, three-fourths of them men, were given selenium or the placebo for an average of 4.5 years.
The group found that the selenium was no better than the placebo at preventing a skin cancer comeback, thus disproving the initial thesis. But it did demonstrate some anticancer properties. For example, the selenium group recorded only 77 cases of secondary cancer compared with 119 in the control group. For prostate cancer, the ratio was 13 cases versus 35; for colorectal cancer, eight versus 19; and for lung cancer, 17 versus 31. The selenium group also experienced 17% fewer deaths, including half as many as controls from a variety of cancers. The trial was scheduled to continue for 2 more years, but Clark pulled the plug early "so that physicians could know of this cancer-prevention potential."
Experts say the findings should be viewed with caution. The study is "very, very encouraging," says Clement Ip, a cancer researcher at Roswell Park Cancer Institute in Buffalo, but he and others say more studies are needed to determine how selenium acts on tumors and how it affects a broader spectrum of patients. There are also questions about its safety when taken on a long-term basis: Selenium can lead to a loss of hair and nails at doses larger than 1 milligram. "We're recommending that we do an additional trial to confirm these results and see how it would extend to other populations," says Clark, in particular women and those with certain cancer types.