National Breast Cancer Foundation, Inc.

I get daily advice from everydayhealth.com I thought this might be useful for some going through treatment. My doctor told me about limiting my antioxidant supplements during treatment, as you'll see below.

The following supplements and other preparations can harm cancer patients or cause dangerous side effects by interacting with chemotherapy or radiation.

1. High doses of vitamins A and C. ... Studies suggest, however, that large doses of antioxidants can lower the effectiveness of chemotherapy and radiation because these treatments work by triggering oxidation in the genes of cells.

2. Soy supplements and other phytoestrogens- red clover and ginseng. One animal study found that genistein, an estrogen found in soy, can prevent tamoxifen from inhibiting breast cancer growth. People with ER-positive cancer should avoid phytoestrogens.

3. Black cohosh. This herbal extract, widely used by women to alleviate hot flashes and other menopausal symptoms, might cause early-stage breast cancer to metastasize, according to research presented in 2003 at a meeting of the American Association for Cancer Research.

The article is more at length on the website I mentioned above.