Washington: New research is prompting a fresh look at the value of vitamin supplements, with some surprising results indicating that taking too many supplements of some could be harmful.

The research is forcing scientists to rethink the use of supplements with antioxidants, which had been seen as beneficial in preventing cancer, heart disease and other ailments.

"Everybody is confused," admitted Toren Finkel, head of the Center for Molecular Medicine at the National Institutes of Health (NIH).

While logic would seem to dictate that taking vitamins and antioxidants should help fight illness and disease, Finkel said in an interview that the clinical data "are pretty consistently showing no benefit."

"So that means we have to go back and think about some of the assumptions we have made along the way in terms of what the mechanism for these diseases are and how things like oxidants play a role in those diseases," he said.

Finkel explained that while it has long been believed that oxidants -- free radicals produced by the body or introduced through external sources such as pollution – were unhealthy, the research paints a more complex picture.

"You have to go back to the lab and try to design experiments you can do a little simpler with cells or animals... to better understand the role of oxidants and vitamins," he said.

"For years, we were using these supplements without knowing the effects on the body."

A study published on October 11 in the United States indicates a 17 per cent increase in the risk of developing prostate cancer among men who take high doses of vitamin E.

Another recent US study conducted among women and published on October 10 revealed that multivitamins -- commonly taken in the United States -- were useless and actually gradually contributed to a higher risk of mortality.

(Agencies)