Soy & Antioxidants After Breast Cancer

Last Modified: March 16, 2008

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Question

Dear OncoLink "Ask The Experts,"

I was told not to take antioxidant vitamins C and E while I was taking chemotherapy for breast cancer. Supposedly, they are taken up by the cancer and used for growth. Should I take them now that I am no longer on chemo and Herceptin? I take Arimidex daily. Also, soy products, are they out also?

Answer

Katrina Claghorn, MS, RD, Registered Dietitian at the Abramson Cancer Center of the University of Pennsylvania, responds:

The advice to avoid antioxidant supplements during chemotherapy is actually due to the potential for interaction with the treatments, not because they will promote tumor growth. So, you can take these supplements now that you are off chemotherapy & radiation treatment.

See these previous questions regarding antioxidants:

Antioxidants during radiation therapy

Antioxidant vitamin supplementation and cancer treatment

It has generally been recommended that women with breast cancer limit their intake of soy foods, since soy contains estrogen-like plant compounds. However, the ACS, in it's report "Nutrition and Physical Activity During and After Cancer Treatment: An American Cancer Society Guide for Informed Choices" (CA Cancer J Clin 2006;56:323-353) states that three servings per day of soy foods is unlikely to be harmful, however they discourage the use of soy supplements, as that may provide too much soy.