What Causes Prostate Cancer? The Answer Continues to Elude Researchers
Nobody knows the underlying cause of prostate cancer. Age increases the risk—about 97 percent of prostate cancers are diagnosed in men age 50 and older—and so does a family history of the disease; having a brother or father with prostate cancer doubles the risk. For reasons not yet understood, prostate cancer occurs in black men at rates more than twice those in white men.
The highest rates of prostate cancer occur in northern Europe and North America. The lowest rates are found in Asia. But when, for example, men move from Japan, where rates are low, to Canada or the United States, their risk goes up. Thus, many researchers think diet is one culprit.
Nothing is certain yet, but scientists have been looking at the following as possible promoters of prostate cancer.
Dietary fat. This has been linked to increased prostate cancer risk since the 1970s, though not in all studies. If fat does play a role, it's unclear whether the amount, type, or source is the key. Some studies point to red meat, specifically to its saturated fat. But the problem could also be the carcinogens formed when meat is fried or grilled. Or it could be that people who eat lots of meat tend to eat fewer healthful foods, like fruits and vegetables, which may protect against cancer.
Zinc. The findings about zinc have been contradictory. An older study from the National Cancer Institute found that men who took more than 100 milligrams of zinc a day from supplements were twice as likely to develop advanced prostate cancer as those who took no zinc. On the other hand, a 2009 study from the Fred Hutchinson Cancer Research Center found that men who took zinc supplements were less likely to develop advanced prostate cancer than those who didn't take the supplements.
Calcium or dairy products. Some studies, including the Physicians' Health Study, have linked high intakes of calcium or dairy to increased risk. But a few have found no connection, and some studies have even found a reduced risk. One complication: Dairy products contain many nutrients besides calcium, some of which may decrease the risk of prostate cancer (such as vitamin D) or increase it (such as saturated fat). Don't stop consuming dairy products for fear of cancer. For one thing, there's some good evidence that dairy products may reduce the risk of colon cancer and hypertension, among other benefits.
Flaxseeds. Some doctors warn men to avoid flaxseeds because of worries about prostate cancer, but there actually has been very little research on this. One laboratory study found that flaxseeds seemed to increase tumor growth. But another, observational study showed that men with prostate cancer who ate flaxseeds daily were able to slow the growth of their cancer. There have been more studies on alpha-linolenic acid (ALA), an omega-3 fatty acid found in flaxseeds, but they, too, have yielded conflicting results. Flaxseeds also contain compounds called lignans, which may have an anticancer effect.
Other. Vasectomy, despite some scary media reports a while back, does not increase the likelihood of prostate cancer, nor does an enlarged prostate (benign prostatic hyperplasia). There is some evidence that obesity increases the chances of developing aggressive prostate cancer or having it recur. On the other hand, men taking a statin for high cholesterol levels may have a reduced risk of aggressive cancer. You may have heard that your sex life—that is, having too few or too many orgasms, either from sex or masturbation—affects the risk of prostate cancer. Studies on this have yielded contradictory findings. Don't worry that your sex life (or lack of one) is harming your prostate.