From CNN Health Correspondent Elizabeth Cohen

ATLANTA (CNN) -- Some 40,000 men die every year from prostate cancer, but a new study says what a man eats may help prevent the disease.

The study, published by the National Cancer Institute, found men who had the highest intakes of the mineral selenium cut their cancer rates by one-half to two-thirds compared to men with the lowest intakes of selenium.

"The notion that vitamins and minerals might prevent prostate cancer is a particularly exciting thing," said Dr. Philip Taylor of the National Cancer Institute.

Selenium is found in fish, meats, grains and seeds in varying amounts. But it is also available in supplements.

Researchers have found that taking 200 micrograms a day cuts the risk of getting prostate cancer.

Other studies have shown that vitamin E might also prevents prostate cancer. Vitamin E and selenium work together as antioxidants to protect cells from damage that could lead to cancer. But doctors are not suggesting that all men start taking supplements for the two nutrients.

"The sum of all the data available to us at this point is not sufficiently compelling or conclusive for us to move into the arena of recommendations," Taylor said.

One problem is that very high levels of selenium can be harmful, causing nails and hair to become brittle. Higher doses can cause neurologic problems and there are reports of selenium overdose deaths.