Antioxidant vitamins cause cancer spread

Far from boosting vitality, antioxidant vitamins might aid the spread of skin cancers around the body, a study in mice has shown this week.

Antioxidants, like vitamins A, C and E, are believed to benefit health by soaking up reactive chemicals called free radicals.

These are byproducts of metabolism that can damage DNA and trigger the genetics changes, or mutations, that ultimately lead to cancer.

Based on this rationale, a number of clinical trials have investigated whether taking antioxidant vitamins can prevent cancer and prolong life.

But far from affording protection, some of these trials were stopped prematurely when excessive numbers of cancer cases began to surface, although it was unclear why. 

Now, working with mice that develop the rodent equivalent of the common human skin cancer malignant melanoma, University of Gothenburg scientist Martin Bergo has shown that if the mice are given antioxidants in their drinking water the tumours spread - or metastasise - twice as often compared with animals not exposed to antixoidant supplements.

Writing in Science Translational Medicine where the work is published, Bergo speculates that although antioxidants are useful at preventing cancer, they might also protect spreading cancer cells equivalently well.

"When cells leave the primary tumour they are subject to oxidative stress," says Bergo. "Antioxidants can help them to resist this insult."

This increases the likelihood that the cells can survive and spread successfully spread to other parts of the body.

"Cancer patients should use antioxidant supplements with caution," warns Bergo.