Antioxidants


 

Various cancer treatments, including many supplements, have multiple mechanisms of action, sometimes including antioxidant action.  Because radiotherapy and many cytotoxic chemotherapies have traditionally been believed to work largely by pro-oxidant action (generation of reactive oxygen species, or ROS), concern has been expressed that the effectiveness of these treatments may be reduced by concurrent use of antioxidants.  However, recent evidence suggests that this emphasis on ROSs may represent an oversimplication of the mechanisms involved.

For a comprehesive review of this issue, see Williams 2009.  Several additional papers dealing with this topic are as follows:

Also note that Aggarwal et al 2006 found that there is a correlation between lower antioxidant levels and increased brain tumor malignancy (ie, a negative correlation between the two), and Il'yasova et al 2009 report a survival benefit for glioma patients associated with increased antioxidant consumption.

Because this issue is controversial, patients need to draw their own conclusions regarding whether to use antioxidants during cancer treatment.  Based mainly on the cited references, the viewpoint of the author of this website is as follows:

  • Supplements which have antioxidant action generally appear to have a protective effect on normal tissue, while also having a net neutral or anti-tumor effect on tumors (rather than reducing the efficacy of radiotherapy or cytotoxic chemotherapy).  However, some supplements may be exceptions to this general rule.
  • When multiple supplements are taken in combination and in generally higher doses, it is likely that their beneficial effects are enhanced while any detrimental effects are reduced.  Supplement combinations are therefore highly preferable to use of single supplements, although of course all supplements in a combination should be carefully selected.

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