Certain combinations seem to raise risk of cancer death

If you're one of the millions of Americans who take vitamins and antioxidant supplements in hopes of improving your health and warding off disease, researchers have some startling news: People who take vitamin and antioxidant supplements are more likely to die of gastrointestinal cancer than those who don't.

The researchers reviewed the results of 14 medical trials that involved more than 170,000 people and found an increase in gastrointestinal cancer deaths when supplements that contained beta-carotene and vitamins A, C and E were involved.

In half of the trials, people who took supplements had a 6 percent higher risk of death from cancers of the esophagus, stomach, pancreas, liver, colon and rectum than those who took a placebo, the review revealed.

But according to the researchers, some combinations of supplements posed an even greater risk.

Supplements containing beta-carotene and vitamin A had a 30 percent higher risk, and supplements that mixed beta-carotene and vitamin E showed a 10 percent higher risk, they reported.

"The indication that mortality in supplement-taking patients was higher compared to placebo has to be explored extensively in all randomized trials," study author Dr. Goran Bjelakovic, a professor of internal medicine at the University of Nis in Serbia and Montenegro, told HealthDay . Results of the review were first published last year in the British medical journal The Lancet .

In contrast, four of the trials that were reviewed showed that selenium might help reduce the risk, the report said.

"The potential protective effect of selenium should be studied in adequate clinical trials," Bjelakovic said.

The National Cancer Institute is conducting a large-scale trial of selenium and vitamin A for prevention of prostate cancer. The trial was started because two studies suggested that it might protect against the disease.

No one knows why antioxidant supplements might be harmful, Bjelakovic said. One theory is that they may interfere with apoptosis, the process by which the body gets rid of abnormal cells.

"Someone who takes supplements can suppress apoptosis and thus can influence the growth of different tumors," Bjelakovic said. "But this is only a hypothesis."

Neither the American Cancer Society nor the National Cancer Institute recommends vitamin supplements as a way to prevent cancer. The cancer society wants people to focus on getting the vitamins and minerals they need by eating a balanced diet.

Dr. David Forman of University of Leeds and Dr. Douglas Altman of Cancer Research U.K. wrote in an editorial in The Lancet that the "prospect that vitamin pills might not only do no good but also kill their consumers is a scary proposition given the vast quantities used in certain communities."

If the findings are correct, " 9,000 in every million users of such supplements will die prematurely as a result," they wrote, adding that the review was "a work in progress and does not offer convincing proof of hazard."

Eric Jacobs, a senior epidemiologist at the American Cancer Society, encouraged people to take actions that are known to prevent cancer.