The study, published in Cancer Cell, unexpectedly found the actual role of anti-oxidants may be to destabilize a tumor's ability to grow under oxygen-starved conditions.

"The potential anti-cancer benefits of anti-oxidants have been the driving force for many clinical and preclinical studies," lead author, Dr.Chi Dang, of The John Hopkins University, said in a statement. "By uncovering the mechanism behind anti-oxidants, we are now better suited to maximize their therapeutic use."

The researchers, who slowed the growth of implanted cancer cells in mice by feeding anti-oxidants, found tumor growth related to a protein -- HIF-1 -- not because anti-oxidants prevent cancer growth by picking up volatile oxygen free radical molecules that damage DNA as previously thought, but because anti-oxidants remove free radicals. Free radicals promote the protein HIF-1 needed by tumor cells to convert sugar to energy without using oxygen.

The authors caution that while vitamin C is still essential for good health, this study is preliminary and people should not rush out and buy bulk supplies of anti-oxidants as a means of cancer prevention.