Antioxidant supplements may actually cause more harm than good for cancer patients, according to an article in the current issue of the American Cancer Society's CA: A Cancer Journal for Clinicians.
The article reviews the data relevant to the use of antioxidant supplements (including vitamins C and E) during chemotherapy and radiation and points out that many cancer patients expect that such supplements will protect them from their illness or from the harmful effects of their treatment. The author concludes, however, that the existing scientific evidence about the effects of antioxidant supplements is highly contradictory and that supplements should therefore not be recommended to cancer patients. In fact, there is reason to believe that taking antioxidant supplements can reduce the effectiveness of cancer treatments such as chemotherapy and radiation, possibly because the supplements protect cancer cells.
A patient should discuss this issue with his or her doctor before tossing their vitamins -- specific deficiencies in a particular person's diet might warrant their taking vitamin supplements during treatment. However, with the body of evidence against antioxidant supplementation apparently growing, people should not rely on them to bestow health benefits -- nor simply assume that "they can't hurt," an attitude the current review debunks.
D'Andrea, GM (2005). Use of Antioxidants During Chemotherapy and Radiotherapy Should Be Avoided. CA Cancer J Clin; 55:319-321