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Vitamin C and cancer therapy

TORONTO, CANADA. The use of vitamin C supplements during chemotherapy is controversial. Most physicians advise their patients to stop supplements during chemotherapy and radiation treatments. Two new studies, just published in the Journal of Orthomolecular Medicine, conclude that this advice is likely very misguided.

The first study painstakingly reviews the medical literature dealing with the use of vitamin C as an adjunct to chemotherapy. A total of 36 studies or reviews concludes that vitamin C is beneficial, 3 that it could be harmful, while one is neutral on the subject. Overall, the author of the study concludes that the use of vitamin C during chemotherapy results in:

  • An increase in survival time
  • Enhancement of the effect of chemotherapy
  • Inhibition of tumour growth
  • A decrease in toxicity
  • An increase in cell death.

Dr. K.N. Prasad of the University of Colorado Health Sciences Center sums up the benefits of combining chemotherapy with vitamin C supplementation in these words, “…. antioxidants (including vitamin C) do not protect cancer cells against free radical and growth-inhibitory effects of standard therapy. On the contrary, they enhance its growth-inhibitory effects on tumour cells, but protect normal cells against its adverse effects.”

The second study reviews studies concerning the use of other antioxidants in conjunction with chemotherapy and radiation therapy. Seven clinical trials evaluated the use of glutathione (intravenous injection) in conjunction with chemotherapy using cisplatin or oxaliplatin. In all cases, neurotoxicity was significantly diminished without affecting the effectiveness of the treatment. Another clinical trial concluded that glutathione is highly effective in preventing diarrhea in patients treated for endometrial cancer with radiation therapy. Selenium (4 mg/day for 4 days before and 4 days after chemotherapy) was found to materially reduce bone marrow suppression and nephrotoxicity induced by cisplatin. Vitamin E (300 IU/day) was found to reduce cisplatin-induced nerve damage from 85% to 31%. Coenzyme Q10 has been found to protect the myocardium from damage during chemotherapy with adriamycin, cyclophosphamide, and 5- fluorouracil. Melatonin has been found to enhance the efficacy of chemotherapy and reduce its toxicity. A cocktail of several antioxidants has been found to increase survival in a group of lung cancer patients undergoing chemotherapy and no decrease in effectiveness was observed in a group of breast cancer patients given a high potency antioxidant cocktail along with their radiation treatments.

The overall conclusion is that there is no convincing evidence that antioxidants impair the effectiveness of chemotherapy and radiation treatments, but a substantial amount of evidence that concurrent antioxidant usage may enhance effectiveness and materially reduce side effects.
Journal of Orthomolecular Medicine, Vol. 19, No. 4, 4th Quarter 2004 (special issue) – The use of vitamin C and other antioxidants with chemotherapy and radiotherapy in cancer treatment

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