Antioxidants are marketed as protective powerhouses that can prevent cell damage caused by free radicals. Free radicals are produced by the body after eating certain foods, exercising, pollution, and being exposed to things like cigarette smoke, certain chemicals, and sunlight. Free radicals can damage cells in the body and change our DNA if they attack in large enough numbers, and this can result in oxidative stress, which has been linked to cancer and other diseases.
Antioxidants defend the body against free radicals, but the term “antioxidant” encompasses a wide range of vitamins, minerals, and other substances — and each one is not interchangeable. Some examples of antioxidants include vitamins A, C, and E, beta-carotene, minerals like selenium and manganese, and flavonoids, phenols, polyphenols, and phytoestrogens which are found in plant-based foods. There are hundreds upon hundreds of antioxidants.
However, breast cancer patients who take antioxidant supplements before and during chemo could increase their risk of recurrence and even death, a study has found.
The study, called the Diet, Exercise, Lifestyle and Cancer Prognosis (DELCaP) study, was published in the Journal of Clinical Oncology. It was led by researchers at the SWOG Cancer Research Network, which is a cancer clinical trials network that’s funded by the National Cancer Institute (NCI) through the National Institutes of Health. Christine B. Ambrosone, Ph.D., who is the chair of the Department of Cancer Prevention and Control at Roswell Park, led the DELCap study.
Ambrosone and her team contacted patients from a previous SWOG trial that had enrolled 2,716 breast cancer patients between 2003 and 2010. The original aim of that trial was to determine the best dose and schedule for high-risk, early-stage breast cancer patients who were given one of three chemo drugs: doxorubicin (Adriamycin), cyclophosphamide (Cytoxan), and paclitaxel (Taxol).
Ambrosone and her team asked each man and woman who had been in this trial if they would answer two detailed questionnaires about their antioxidant use before and during chemo. They were asked about their use of the following supplements: vitamin C, vitamin A, vitamin E, coenzyme Q10, carotenoids (such as beta-carotene, lycopene, selenium, and lutein), any antioxidant, multivitamins, vitamin D, vitamin B6, vitamin B12, iron, folic acid, calcium, omega-3 fatty acids, glucosamine, melatonin, and acidophilus.
It’s important to note that the DELCap study is an observational study that relies on the patients’ memory. Though 2,014 of the patients agreed to complete the surveys initially, only 1,134 patients ended up completing both. Of these people, 18% took at least one antioxidant every day, and 44% took multivitamins. These self-reported rates are low compared to rates of supplement use in other studies, especially antioxidants.
Researchers found that the patients who took multivitamins had no significantly better or worse outcomes than other patients. Likewise, the patients who took antioxidants only before chemo or only during chemo had no better or worse outcomes.
However, the patients who took antioxidants both before and during chemo — specifically vitamins A, C, E and carotenoids and Coenyzme Q10 — did. Patients who took any of those antioxidants both before and during chemo were 41% more likely to have breast cancer recur and 40% more likely to die. Patients who took vitamin B12 both before and during chemo were 83% more likely to have breast cancer recur and about twice as likely to die. Patients taking iron supplements both before and during chemo were 91% more likely to have breast cancer recur, and patients taking omega-3 fatty acids both before and during chemo were 67% more likely to have breast cancer recur.
This isn’t the first time antioxidant use in cancer patients have been studied, but it is the first that focuses on the effects of supplements specifically during breast cancer treatment. Studies over the last couple of decades have shown that antioxidants like vitamin E, beta-carotene, and selenium can increase risk of certain cancers, cause cancer to recur, or interfere with the effects of chemotherapy. In the Selenium and Vitamin E Cancer Prevention Trial (SELECT), researchers found that vitamin E supplements increased the risk of prostate cancer in healthy men.
However, one study found positive news about vitamin C use. That study was led by the director of Yale Cancer Center and found that vitamin C could be beneficial specifically for colorectal cancer patients undergoing chemo.
Despite their cancer-fighting reputation, antioxidants may not be suitable for breast cancer patients.
“Patients using any antioxidant before and during chemotherapy had an increased risk of their breast cancer returning and, to a lesser degree, had an increased risk of death. Vitamin B12, iron, and omega-3 fatty acid use was also associated with poorer outcomes,” said Ambrosone.
“People diagnosed with any cancer should talk with their doctors about whether they should be taking vitamins or other supplements,” she continued. “I’d recommend that they try to get their vitamins and minerals — including antioxidants — from food. With a healthy and balanced diet, you can get all the nutrients your body needs, even while undergoing chemotherapy.”
C. Dixon likes to read, sing, eat, drink, write, and other verbs. She enjoys cavorting around the country to visit loved ones and experience new places, but especially likes to be at home with her husband, son, and dog.