Antioxidant vitamin supplementation and cancer treatments

Ellen Sweeney, RD
Last Modified: June 16, 2002

Dear OncoLink "Ask The Experts,"
I administer chemotherapy and have recently heard of a new study that acknowledges vitamin therapy in cancer patients receiving chemotherapy as non-therapeutic. Some of my patients tell me that the study states that vitamins help enhance cancer growth and cell resistance to chemo. Do you know of this study and where I can get a copy?

Ellen Sweeney, RD, Registered Dietitian at the Abramson Cancer Center of the University of Pennsylvania, responds:

There are actually several studies that show potential interactions between antioxidant vitamin supplementation (Vitamins C, E, and A for example) and cancer treatments, both radiation and chemotherapy. The theory is that since antioxidants protect the body's cells from oxidation or damage, that taking excess amounts of them may protect the cancerous cells as well from oxidative cancer treatments, therefore decreasing the effectiveness of the treatments. Since research is not yet conclusive in this area, it is usually recommended that patients avoid extra antioxidant supplements through out treatment. A standard multivitamin that provides 100% of the RDI for vitamins and minerals is okay. Here are some references to studies below that can be found in their respectable journals. The last one listed was done specifically with vitamin C and cancer cells and showed that cancer cells consume large amounts of vitamin C, therefore possibly protecting them from radiation or chemotherapy. This may be the study your patients referred to although it is not that recent. There have also been large studies that some patients, particularly those with lung cancer, have significantly worse overall survival with antioxidant supplementation.

Hamilton KK. Antioxidant supplements during cancer treatments: where do we stand? Clinical Journal of Oncology Nursing. 2001; 5(4): 181-182.
Labriola D, Livingston R. Possible interactions between dietary antioxidants and chemotherapy. Oncology. 1999; 13:1003-1011.
Lamson DW, Brignall MS. Antioxidants in cancer therapy: their actions and interactions with oncologic therapies. Alternative Medicine Review. 1999; 4:304-329.
Agus DB, Vera JC, Golde DW. Stromal cell oxidation: a mechanism by which tumors obtain vitamin C. Cancer Research. 1999; 59(18): 4555-8.