Are Antioxidants Safe During Chemotherapy and Radiation Treatment?
By Alan R. Gaby, MD
Healthnotes Newswire (September 29, 2005)—A new report concluded that cancer patients should avoid antioxidant supplements while receiving chemotherapy or radiation treatment,1 prompting a feature article in the Wall Street Journal,2 which argues that antioxidants could block the beneficial effects of standard cancer therapy; however, the available scientific evidence does not support the view that people undergoing cancer treatment should always avoid antioxidant supplements.
The authors of the new report pointed out that radiation therapy and some chemotherapy drugs act by producing free radicals—highly reactive chemicals that can damage both cancer cells and normal cells. Antioxidants such as vitamin C, vitamin E, coenzyme Q10, glutathione, and selenium can reduce the toxicity of free radicals.3 While supplementing with antioxidants might, therefore, protect healthy cells from the negative effects of radiation or chemotherapy, the authors expressed concern that taking these supplements might protect cancer cells even more than normal cells, thereby inhibiting the beneficial effect of standard treatment.
There are situations in which antioxidant supplementation would be undesirable for cancer patients, but the issue is actually a lot more complicated than the article indicated. Although many chemotherapy drugs do induce the formation of free radicals, their anticancer effects do not, in general, seem to depend on the formation of these free radicals. Consequently, antioxidant supplementation may in some circumstances help prevent free-radical-induced side effects without inhibiting the positive effects of the chemotherapy.
In animal studies, giving antioxidants along with certain chemotherapy drugs did not reduce the anticancer effects of the drugs and it increased survival times, compared with the survival of animals that received chemotherapy alone. In studies in humans with cancer, coenzyme Q10 prevented the heart damage that often occurs with the cancer drug adriamycin without inhibiting its anticancer effect.45 In another study of women with ovarian cancer, supplementation with selenium along with chemotherapy (cisplatin plus cyclophosphamide) prevented the loss of appetite, hair loss, vomiting, and decline in white blood cell counts that occurred when the chemotherapy was given by itself.6 Intravenously administered glutathione prevented cisplatin-induced nerve damage in people with stomach cancer.7 Furthermore, glutathione did not interfere with the anticancer effect of cisplatin; on the contrary, there was a trend toward a better treatment response and longer survival in people given glutathione group than in those receiving chemotherapy alone.
With regard to mixing antioxidants and radiation therapy, there is very little research in humans, and the recommendation made in the article was based primarily on theory and test tube studies. However, one preliminary study in women with cancer of the cervix suggested that antioxidants (vitamin C plus bioflavonoids) might enhance the effects of radiation therapy. Of the women who received antioxidants along with radiation therapy, 100% had a favorable response to the treatment, whereas only 59% of women receiving radiation therapy by itself had a positive response.8
We still have a great deal to learn about the interactions between cancer treatments and antioxidant supplements. Whether or not an antioxidant supplement would be helpful, harmful, or neutral presumably depends in part on the specific antioxidant (and its dose), the chemotherapy drugs being used, the type of cancer being treated, and the type of diet the patient is consuming. We simply do not know enough at the present time to make a categorical statement that antioxidants should never be taken along with standard cancer therapy. However, since there is at least theoretical potential for harm, people who are undergoing cancer therapy should seek the advice of a qualified professional before supplementing with antioxidants.
1. D’Andrea GM. Use of antioxidants during chemotherapy and radiotherapy should be avoided. CA 2005;55:319–21.
2. Parker-Pope, Tara. Cancer and Vitamins: Patients Urged to Avoid Supplements During Treatment; The Wall Street Journal 2005 Sep 20 Sect. D:1.
3. Weijl NI, Cleton FJ, Osanto S. Free radicals and antioxidants in chemotherapy-induced toxicity. Cancer Treat Rev 1997;23:209–40.
4. Cortes EP, Gupta M, Chou C, et al. Adriamycin cardiotoxicity: early detection by systolic time interval and possible prevention by coenzyme Q10. Cancer Treat Rep 1978;62:887–91.
5. Judy WV, Hall JH, Dugan W, et al. Coenzyme Q10 reduction of adriamycin cardiotoxicity. In: Folkers K, Yamamura Y, eds. Biomedical and Clinical Aspects of Coenzyme Q, Vol. 4, Elsevier, 1984:231–41.
6. Sieja K, Talerczyk M. Selenium as an element in the treatment of ovarian cancer in women receiving chemotherapy. Gynecol Oncol 2004;93:320–27.
7. Cascinu S, Cordella L, Del Ferro E, et al. Neuroprotective effect of reduced glutathione on cisplatin-based chemotherapy in advanced gastric cancer: a randomized double-blind placebo-controlled trial. J Clin Oncol 1995;13:26–32.
8. Cheraskin E, Ringsdorf WM Jr, Hutchins K, et al. Effect of diet upon radiation response in cervical carcinoma of the uterus: a preliminary report. Acta Cytologica 1968;12:433–38.
An expert in nutritional therapies, Chief Medical Editor Alan R. Gaby is a former professor at Bastyr University of Natural Health Sciences, where he served as the Endowed Professor of Nutrition. He is past-president of the American Holistic Medical Association and gave expert testimony to the White House Commission on Complementary and Alternative Medicine on the cost-effectiveness of nutritional supplements. Dr. Gaby has conducted nutritional seminars for physicians and has collected over 30,000 scientific papers related to the field of nutritional and natural medicine. In addition to editing and contributing to The Natural Pharmacy (Three Rivers Press, 1999), and the A–Z Guide to Drug-Herb-Vitamin Interactions (Three Rivers Press, 1999), Dr. Gaby has authored Preventing and Reversing Osteoporosis (Prima Lifestyles, 1995) and B6: The Natural Healer (Keats, 1987) and coauthored The Patient's Book of Natural Healing (Prima, 1999).
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