Does selenium truly protect against cancer? A five-year study involving 42,000 volunteers in the United States and five European countries (Denmark, Finland, Sweden, the United Kingdom and the Netherlands) is under way to confirm the value of daily selenium supplements in the war on cancer.

An editorial in the Journal of the National Cancer Institute suggests the study may be one trial away from proving what's been called "the tremendous potential public health benefits" of improving public access to selenium. Researchers will be looking for the effects of selenium in protecting against a wide range of cancer types, including but not limited to prostate cancer.

The study is comparing three different dosages of selenium and is, according to the research team, large enough to detect a 10 percent reduction in total cancer incidence over the five-year period. Both men and women, ages 60 to 74, are being enrolled.

The first phase of the study has begun in two countries and is due to start in the United States as soon as funding is finalized. That's expected sometime this fall.