Low blood levels of the mineral selenium may mean a man has an increased risk of prostate cancer.

A number of studies have indicated that selenium intake offers some protection from prostate cancer. And the new findings support the hypothesis that supplemental selenium may reduce the risk of prostate cancer.

Selenium is a trace mineral found in foods such as Brazil nuts and walnuts. It acts as an antioxidant, helping to neutralize byproducts of normal metabolism called free radicals, which can damage cells and contribute to cancer.

In the current study, the researchers evaluated selenium levels in blood samples from 52 men with prostate cancer. These men had provided blood samples before they were diagnosed with prostate cancer and again after their diagnosis. This group was compared with 96 otherwise healthy men who had periodically had their blood selenium levels measured.

The investigators found that prostate cancer risk was significantly higher in the group of men with the lowest selenium blood levels, compared with the groups with higher levels.

Low selenium is associated with a 4- to 5-fold increased risk of prostate cancer.

Low selenium levels remained a risk factor even after the researchers took into account other factors such as age, smoking and alcohol use.

The Journal of Urology December 2001;166:2034-2038