Thursday October 30, 2008, 2008 (foodconsumer.org) -- A study sponsored by the National Cancer Institute found that supplementation of vitamin E and selenium may do more harm than good in men with regard to the risk of prostate cancer.

The Selenium and Vitamin E Cancer Prevention Trial (SELECT) showed that taking vitamin E or selenium supplements or combination of the two did not seem to reduce the risk of developing prostate cancer in men age 50.

Even worse, men who took only vitamin E had a small increase in their risk for prostate cancer and men who only took selenium had a small increase in their risk for adult onset diabetes although the increases were not statistically significant.

The study was conducted at more than 400 clinical sites in the United States, Puerto Rico and Canada and involved 35,000 men age 50 or older.

The NCI said in a statement that study staff will continue to monitor the participants' health by performing regular digital rectal exams and PSA (prostate-specific antigen) tests to detect prostate cancer in next three years to see if there is a long term effect of the supplementation.

“SELECT was always designed as a study that would answer more than a single question about prostate cancer,” said Eric Klein, M.D., a study co-chair for SELECT, and a physician at the Cleveland Clinic. “As we continue to monitor the health of these 35,000 men, this information may help us understand why two nutrients that showed strong initial evidence to be able to prevent prostate cancer did not do so.”

Prostate cancer is the most common type of cancer in men except for skin cancer in the United States.   In 2008, the disease is expected to be diagnosed in 186,000 men and 28,660 will die from the disease.

An early study led by Jiyoung Ahn, Ph.D., and Richard Hayes D.D.S., Ph.D., of the National Cancer Institute in Bethesda, Md. and colleagues and reported in May 2008 suggests that taking vitamin D may not help prevent prostate cancer because the serum levels of this vitamin D did not differ much between patients and healthy controls.   But that was not a trial and did not prove that taking the vitamin is ineffective at protecting against the disease.

A health observer commented that readers should not be disappointed at the finding by the NIC because it is not uncommon for the government agency to find something negative.   He said men got to eat what men got to eat.   There are still many things men may do to reduce the risk of prostate cancer.

Many previous studies have associated certain foods or diets with lower risk of prostate cancer.   Some studies showed that plant-based diets are protective against the disease.

A review led by Berkow SE from George Mason University and colleagues and published in the September 2007 issue of Nutrition Review showed that eating plant-based diets may help patients with prostate cancer.

The researchers reviewed eight observational studies and 17 intervention or laboratory trials on the effect of plant-based diets and plant nutrients on both the progression and clinical outcome of prostate cancer.

Black tea, green tea, lycopene supplements, soy isoflavones, broccoli, cauliflowers, pomegranate juice, and salmon are some of protective foods that men can eat to reduce the risk of prostate cancer, according to numerous previous studies.

At least one study led by   Ulrike Peters and colleagues from the Cancer Prevention Program, Fred Hutchinson Cancer Center, Seattle, WA and other organizations even found that high dietary intake of selenium may reduce risk of prostate cancer in groups of men who also took vitamin E and those who took multivitamins.

Studies on the effect of vitamin D are also inconsistent.   Some studies suggest that taking high doses of vitamin D may help prevent spreading of aggressive prostate cancer. But Ahn’s study found that there was an association between high serum levels of vitamin D and increased risk for aggressive disease.