Vitamin C, which is widely touted as cancer preventive, is on display June 15, 2001 in Miami, FL. (Photo by Joe Raedle/Getty Images)

Selenium and vitamins E and C do not reduce the risk of prostate cancer and other cancers in men, two large studies released Tuesday suggest.

The findings are described as disappointing because previous studies had suggested the vitamins and selenium — a chemical element that in trace amounts is necessary for cellular function — were associated with reduced risk of certain cancers.

The two studies will be published in the Jan. 7 issue of the Journal of American Medicine but are being released early because of the public health implications.

Despite uncertainty about the long-term health effects or benefits, more than half of U.S. adults take vitamin supplements, and vitamins E and C are among the most popular individual supplements, according to background information in the article.

In Canada, an average of 12 men die of prostate cancer every day, while one in every eight men develop the disease in their lifetime.

Dr. Peter Gann of the University of Illinois at Chicago, who was not involved in the studies, describes the finding as "disappointing news" in an accompanying editorial.

"Single-agent interventions, even in combinations, may be an ineffective approach to primary prevention in average-risk populations. It may be time to give up the idea that the protective influence of diet on prostate cancer risk … can be emulated by isolated dietary molecules given alone or in combination to middle-aged and older men," he writes.

Given to healthy men

In the first study, Dr. Scott Lippman of the University of Texas, Dr. Eric Klein of the Cleveland Clinic Lerner College of Medicine, and colleagues conducted trials to examine the effects of selenium and vitamin E, alone or in combination, on the risk of prostate cancer in relatively healthy men.

The trial included more than 35,000 men over age 50 from the U.S., Canada and Puerto Rico. The participants were randomly assigned to receive one of four treatments between August 2001 and June 2004 for a planned minimum followup of seven years.

The four treatments were 200 micrograms/day of selenium; 400 international units per day of vitamin E; selenium and vitamin E together; or a placebo.

In September, the researchers cut their study short after an independent data- and safety-monitoring committee said there was no convincing evidence of benefit.

The second study followed nearly 15,000 male doctors aged 50 and older who took 400 IU of vitamin E and 500 mg of vitamin C supplements a day.

Over eight years, Dr. Michael Gaziano of Brigham and Women's Hospital and colleagues found no reduction of risk of prostate cancer or other cancers, including colorectal, lung, bladder and pancreatic.

"These data provide no support for the use of these supplements in the prevention of cancer in middle-aged and older men," the authors concluded.