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The problem with these supplements is that they lack well conducted clinical studies and clinical trials. The makers of these supplements also lack transparency, and what they claim are not evaluated by regulatory boards such as the FDA. So, I'm afraid that the answer to your question is "no one actually knows for sure".
There are some supplements that are studies in conjunction with chemotherapy, like glutathione which can lower the effectiveness of certain chemo drugs. St-John's Wort was also found to interact with the way some chemotherapy drugs are being metabolized in the liver.
Regards.