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Last month a study of over 1,000 people with breast cancer found some worrying evidence that certain nutritional supplements could reduce the chance of survival from the disease and increase the chance that the cancer would recur after treatment. The main findings were:
The research was published in the Journal of Clinical Oncology and led by scientists at the SWOG cancer research institute.
“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 Christine B. Ambrosone, PhD, of Roswell Park Comprehensive Cancer Center and leader of the study.
People with cancer are often bombarded with information, especially at their time of diagnosis and this is not always from their medical team. So what does a patient think about this new work?
“Getting diagnosed with breast cancer was a huge shock – not just for me but everyone who knew me,” said Liz O'Riordan, a Consultant Breast Surgeon from the U.K. with recurrent breast cancer. “When I started chemotherapy I was told to tell my oncologist about any supplements or vitamins I took or wanted to take because they can interfere with the chemotherapy drugs and stop it working,” she added.
This advice is widely repeated on many reputable cancer websites. The American Cancer Society states that “So far, no dietary supplements (including vitamins, minerals, and herbal products) have been shown to clearly help lower the risk of breast cancer progressing or coming back,” along with the advice to patients to speak to a member of their healthcare team if a patient is considering taking supplements.
“I was never going to take anything that might reduce my chances of survival. However I’m sure some cancer patients are desperate for the promise of a cure and will ignore this advice whilst they take every supplement recommended to them,” said O’Riordan.
Vitamin supplements, particularly multivitamins have had a rough couple of years with several studies questioning whether they have any positive effects on health at all. This analysis of almost half a million people by Johns Hopkins researchers entitled “Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements,” found that multivitamin use did not decrease the risk of cancer, heart disease or help with cognitive decline. Experts recommend that the best way to ensure an adequate intake of vitamins and minerals is to eat a healthy, balanced diet.
So if many popular nutritional supplements are of questionable benefit for healthy people and increasingly not often recommended by healthcare professionals, where are people with cancer getting the message that they should take these?
“As I struggled through chemotherapy, I was bombarded with advice; some of it helpful, some of it potentially dangerous. I remember being trolled by strangers who were adamant that I should take iodine supplements and turmeric capsules or have multivitamin drips,” said O’Riordan.
Advice to take various weird and wonderful supplements is all over the internet and although many of the authors of these blogs, websites and social media groups may mean well, the new study now provides evidence that they may be causing harm to patients who follow this advice.
“It’s great to finally see some evidence that supplements can do more harm than good during chemotherapy, help doctors persuade patients to stop taking them during treatment and more importantly, help patients explain to well-wishers why their recommended tablets and potions could be dangerous,” said O’Riordan.
However, it must be noted that although the study was well-constructed, there were issues with low numbers of patients taking individual supplements and many people are calling for more work to solidify the findings of the work.
“These results are interesting but as the study authors point out themselves, the number of women taking any individual supplement in this study is small, and therefore the true magnitude of risk isn’t something we can say with certainty,” said Dr. Kevin Cheung, a physician-scientist at Fred Hutchinson Cancer Research Center in Seattle.
The study also found that there was no evidence that some supplements such as multivitamins or vitamin D were harmful and many people are calling for more research to figure out exactly which supplements are harmful and more to the point, why.
“This study should inspire future laboratory work to get at why and when supplements are associated with worse outcomes. A more nuanced understanding could reveal which supplements fuel the growth and metastasis of cancer cells and should be avoided,” said Cheung.
Of course many people have a clinical need for supplementation, such as people who have anemia or severe vitamin B12 deficiency. The issue appears to be with people choosing to take supplements with no indication that they need them.
“At many institutions including ours, for those with more questions, we recommend consulting our integrative medicine service who can provide guidance on what supplements are safe or not safe to take with treatment,” said Cheung.
“I'd recommend [to people diagnosed with cancer] 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 chemo,” said Ambrosone.
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