U. S. researchers have said that high doses of antioxidant supplements such as vitamins C and E, not foods, may actually increase cancer risk.

It has been reported that Dr. Eduardo Marban, director of the Cedars-Sinai Heart Institute in Los Angeles, and his research team made the discovery accidentally while trying to reduce the genetic abnormalities that occurred when trying to multiply human cardiac stem cells.

In laboratories, stem cells are composed of 20 percent oxygen, but cells growing in human tissue are exposed to just 3 percent to 5 percent oxygen.

Marban said that higher concentration of oxygen in lab-grown stem cells resulted in 9 percent of the cells being rejected because of genetic abnormalities.

Marban said in a statement, "We sought to counter that oxidation problem by adding high doses of antioxidants."

Published online ahead of print in the July issue of the journal Stem Cells, the study found there is a danger zone for the cells exposed to antioxidants to develop genetic abnormalities that predispose to cancer.

Marban further said, "Taking one multivitamin daily is fine, but a lot of people take way too much because they think if a little is good, a lot must be better. If you are taking 10 or 100 times the amount in a daily multivitamin, you may be predisposing your cells to developing cancer, therefore doing yourself more harm than good."

It was further stressed by Marban that the finding applied only to excessive supplements, not to foods that are rich in antioxidants such as oranges, blueberries and peanuts. (With Inputs from Agencies)