Selenium may worsen prostate cancer in some

Higher selenium levels in the blood may worsen prostate cancer in some men who already have the disease, revealed by researchers.

The new study was conducted by researchers at Dana-Farber Cancer Institute the University of California, San Francisco.

A higher risk of more-aggressive prostate cancer was seen in men with a certain genetic variant found in about 75 percent of the prostate cancer patients in the study. In those subjects, having a high level of selenium in the blood was associated with a two-fold greater risk of poorer outcomes than men with the lowest amounts of selenium.

The research findings suggest that “if you already have prostate cancer, it may be a bad thing to take selenium,” says Philip Kantoff, MD, director of Dana-Farber’s Lank Center for Genitourinary Oncology.

The lead author is June Chan, ScD, of the University of California, San Francisco.

Selenium is a mineral found widely in rocks and dirt. Small amounts of selenium are essential for health: 40 to 70 micrograms is the recommended daily intake. In recent years, supplemental selenium has been sold and promoted as a means of preventing prostate cancer, largely based on observational studies that found higher risk of prostate cancer incidence and mortality in areas of the country that are naturally low in selenium.

Scientists examined banked blood samples, DNA, and medical records of 489 male Dana-Farber patients diagnosed between 1994 and 2001 with localized or locally advanced prostate cancer.

Simply having a high level of selenium was associated with a slightly elevated risk of aggressive prostate cancer. But the risk was much more strongly affected by the interaction of selenium levels and whether the patient had a certain variant of the SOD2 gene.

Men with the highest selenium levels and the “AA” form of the SOD2 gene were 40 percent less likely to have been diagnosed with aggressive prostate cancer than the men with same gene form but low levels of selenium.

Source: Dana-Farber Cancer Institute, USA

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