Breast cancer patients who undergo chemotherapy should avoid taking certain nutritional supplements, such as antioxidants. A new study from Buffalo (USA) suggests that these supplements counteract the efficacy of the chemotherapy, resulting in a higher risk of recurrence of the cancer, or even death. The Journal of Clinical Oncology published findings from this study in its December issue.
According to author dr. Christine Ambrosone, there is strong evidence that antioxidants impair chemotherapy’s ability to kill of cancer cells by counter-acting oxidative stress. She points out that it has been common practice in the USA to advice patients on chemotherapy to stop their intake of supplements, but so far there has never been any empirical data to support that advice.
Ambrosone and her team analyzed data from an existing large study regarding diet, exercise, lifestyle and cancer. Over 1100 patients had filled in questionnaires, and had been followed for over 6 years. Of the 1134 patients, 20% used to take some form of nutritional supplement prior to chemotherapy, and 13% continued to use supplements during their treatment.
Patients who used antioxidants, such as carotenoids and vitamin A,C and E, had 41% more chance of their cancer returning within 6 years, and a 40% higher chance of dying in that period. Other supplements, such as iron, vitamin B12 and omega-3 fatty acids turned out to be even more detrimental. Women who took vitamin B12 during their chemo treatments had an 83% higher risk of their cancer returning, and a 22% higher risk of death. Women who took omega-3 supplements showed a 67% higher risk of relapse, whereas intake of iron resulted in a 79% higher risk.