A population case-control study on the relationship between selenium and bladder cancer was published in the International Journal of Urology (2006; 13(9): 1180-4). The subjects were 178 patients with bladder cancer and 362 healthy controls.  Researchers found that people with the highest levels of selenium had a 0.30 odds ratio for getting bladder cancer when compared to patients with the lowest selenium levels. The study suggests an inverse relationship between selenium levels and the risk of bladder cancer.

Another study, appearing in the journal Cancer Prevention Research (2009 January;2(1):70-3), looked at selenium levels in over 1,800 subjects by measuring selenium levels in the toenail. The subjects included healthy controls and patients with bladder cancer. Those with higher selenium levels had a decreased risk of bladder cancer. Adequate selenium may be important for the health of the immune system and for the prevention of several diseases, including cancer.