Can Selenium Stop Prostate Cancer?

Prostate cancer is the most commonly diagnosed cancer among American men, according to the Washington, D.C.-based National Cancer Institute (NCI). However, the bulk of these cancers remain latent, and only a small number progress to cause illness or death. In 1997, NCI estimated 210,000 new cases were diagnosed and 42,000 men died as a result of their cancer. A recent study suggests eating foods rich in the trace mineral selenium—organ meats, seafood and whole grains—may help men reduce their risk of advanced prostate cancer.¹

To determine this, researchers from Harvard University studied 33,737 male health professionals, all of whom provided toenail clippings that were stored for later analysis. Because the selenium content of toenails is a good indicator of selenium status, the stored material provided an opportunity to match selenium status before diagnosis with a later occurrence of prostate cancer. The study began in 1987 as part of a prostate cancer study in which selenium was not supplemented.

Participants filled out questionnaires during the course of the study, and all new cases of prostate cancer were recorded. From 1989 through 1994, the group reported 181 new cases of advanced prostate cancer. Each case was matched with a control subject (one who did not have prostate cancer) of the same age and smoking status. The toenail samples of both the cases and controls were analyzed for selenium.

Results showed the mean toenail selenium level was significantly higher in control subjects than in cancer subjects. When subjects in the highest 20 percent for selenium status were compared with those in the lowest 20 percent, those with the highest selenium status were half as likely to get prostate cancer as those with the lowest levels.

While this study shows an association between low selenium levels and occurrence of prostate cancer, it does not show that the relationship is causal. Additional well-planned, controlled studies are needed to show whether raising selenium levels can protect against this disease. However, this report adds another strong piece of supportive evidence.

—S.B.

References

1. Yoshizawa K, etal. Study of prediagnostic selenium level in toenails and the risk of advanced prostate cancer. J Nat Canc Inst 1998 Aug 19;90(16):1219-24.