Men, take note: The evidence for an easy, inexpensive way to prevent your number-one malignancy—prostate cancer—has reached critical mass. Prostate cancer strikes nearly 200,000 men each year and kills more than 30,000, and it can devastate a man’s sex life. But you may be able to avoid that fate by taking a simple daily supplement of the mineral selenium.
In fact, the evidence for selenium has swelled into a tide even the FDA couldn’t ignore. Last February the agency, notoriously reluctant to give any supplement its imprimatur, allowed health claims to be made for selenium, stating that the mineral may reduce the risk of certain cancers. Although it permitted only a qualified claim—research has yet to determine exact dosages and other factors that may affect the supplement’s effectiveness—the agency’s action put selenium on the map as one of the most powerful weapons in our anti-cancer arsenal.
Research first linked higher levels of selenium to reduced cancer risk in the 1960s. But the results of a ten-year study, published in 1996, thrust the mineral into the spotlight. The late Larry Clark, then associate professor of epidemiology at the University of Arizona Cancer Center, had done a series of studies linking skin cancer to low selenium levels and decided to put his theory to the ultimate test: a double-blind, placebo-controlled study. For an average of four and a half years, 1,312 volunteers took either brewer’s yeast tablets containing 200 micrograms of selenium or placebos.
Clark was surprised to find that the selenium had no effect on the skin cancers he was studying. But, as another selenium expert put it, “Then serendipity stepped in.” Poring over his data, Clark noticed that the three leading cancers in men—lung, prostate, and colon—were significantly lower in the people taking selenium. He redesigned the study to collect more complete information and ultimately found a moderate decrease in cancer overall, but a whopping 63 percent lower risk of prostate cancer among the selenium-takers. (The study found no decrease in cancers for women, but since it focuses primarily on men—as does most subsequent selenium research—the jury’s still out on whether women can benefit from supplements, too.)
Other researchers rushed to follow Clark’s trail. In 1987, at Harvard, 33,737 male health professionals were asked to send in their toenail clippings, a measure of long-term selenium intake. Four years later, when the researchers matched the men to their clippings, they found that the rate of prostate cancer had decreased by one-half to two-thirds in those with the highest selenium levels.
But perhaps the most exciting evidence of selenium’s powers comes from a bunch of elderly beagles. As a comparative oncologist (an expert in cancers affecting both humans and animals), David Waters, of Purdue University, knew that beagles also tend to develop prostate cancer with age, and that selenium had been shown to lower the risk in men. But he wanted to know how selenium worked its magic. So he assembled 49 dogs that were roughly equivalent in age to 65-year-old men and gave 39 of them 200 micrograms of selenium (twice what most Americans get from their daily diet). They also nibbled a brand of dog food that contains trace levels of selenium. The other ten pooches ate only the dog food.
The results, published last year in Journal of the National Cancer Institute, were impressive. After seven months, dogs who chewed selenium supplements along with their daily chow fared much better than those who didn’t. Among the untreated dogs, nearly 80 percent of their prostate cells had extensive DNA damage, compared with 57 percent of cells from animals who got the extra selenium. When scientists examined the prostate tissue of all the dogs, they didn’t find greater antioxidant activity in the selenium-takers—the mechanism they expected to be responsible for curbing cell damage—but they did find a much higher level of something called apoptosis.
Apoptosis is a normal biological process that, in effect, helps damaged cells commit suicide. When cells deteriorate or go haywire because of radiation, viral infection, aging, or the kind of aberrant growth that occurs with cancer, this process shuts them down, limiting the damage they can do. Waters’ group found twice the level of apoptosis in the prostate tissue of the selenium-supplemented dogs as in the untreated beagles.
Does this mean men should all immediately begin taking 200 micrograms of selenium a day?
Many experts say yes, among them pioneering physician Dean Ornish, in Sausalito, California. “If a drug company came out with a medication that could reduce the risk of cancer to this degree, just about every doctor in the country would prescribe it,” he says. “The potential benefit is great, the cost is very low, and so are the side effects and risks.” Ornish’s soon-to-be-reported Prostate Cancer Lifestyle Trial includes selenium supplements along with a low-fat plant-based diet and other cancer-reducing strategies.
John Finley, a scientist at the Human Nutrition Research Center in Grand Forks, North Dakota, also thinks men should be taking a daily supplement with 100 to 200 micrograms of selenium. (Until more research is done, it can’t hurt for women to hedge their bets against cancer with a supplement, too.) Most people have blood levels of selenium of about 120 mcg just from diet alone, says Finley, but it takes around 300 mcg to get the benefits.
Some experts recommend even more. Stephen Strum, former medical director of the Prostate Cancer Research Institute in Los Angeles, thinks it’s perfectly safe to take daily doses in the 400 to 800 mcg range—the amount physicians routinely recommend in England. But don’t overdo it. In doses above 1,000 micrograms, selenium can lead to a disease called selenosis, which may cause neurological problems, hair loss, and deformed nails. Anyone taking large amounts should watch for side effects—oddly enough, the first sign that you may be headed toward selenosis is a garlicky smell on your breath and skin—and work with a physician to find the right dosage.
Some experts think selenium might work best when taken along with vitamin E. A vast ten-year study, called SELECT (Selenium and Vitamin E Cancer Prevention Trial), sponsored by the National Cancer Institute, was launched in 2001 to find out. In the meantime, you can’t go wrong with a daily dose of both supplements.
Tell your friends about them, too—including any beagles you know.
Selenium User’s Guide
What is it? A trace mineral that’s been shown to prevent prostate cancer, and possibly other cancers as well.
- Dosage: Many experts recommend a multivitamin with 100 to 200 micrograms of selenium. But daily doses in the 400 to 800 mcg range are considered safe, too.
- Risks: In amounts above 1,000 mcg, the mineral can lead to a disease called selenosis, which causes neurological problems, hair loss, and deformed nails.
By Susan Edmiston