Taking certain vitamins during breast cancer chemo tied to recurrence, death

https://news.yahoo.com/taking-certain-vitamins-during-breast-212802391.html

By Linda Carroll
,Reuters•December 23, 2019

Patients with breast cancer who use supplements during chemotherapy may be at an increased risk of recurrence and death, a new study suggests.

Use of dietary supplements that boost levels of antioxidants, iron, vitamin B12 and omega-3 fatty acids appeared to lower the effectiveness of chemotherapy, researchers report in the Journal of Clinical Oncology.

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"It's thought that antioxidants might interfere with the ability of chemotherapy to kill cancer cells," Ambrosone explained. "One way chemotherapy works is by generating lots of oxidative stress. The thinking is that antioxidants may block oxidative stress and make chemotherapy less effective."

Doctors have been advising patients for a number of years not to take antioxidants during chemotherapy, Ambrosone said. "But there was no strong empirical data for that recommendation," she added.

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"There has been ongoing theoretical concern about the fact that while antioxidants may protect normal cells from the toxic effects of chemo, we don't know that they don't also protect the cancer cells," Tiersten said in an email. "Now we have solid data to back up that concern. I am a bit surprised by the magnitude of the effect, a 41% increase in the risk of recurrence for patients taking these supplements. I have always told patients on chemotherapy that the best way to get their vitamins is through a well-balanced diet and will continue to do so given these data."