Women with breast cancer who take antioxidant supplements during their chemotherapy or radiotherapy treatment have been found to have higher rates of mortality and cancer recurrence.
At least when it comes to reducing the risk of cancer, diets high in fruits and vegetables (which are also high in antioxidants) can be protective. The question of if high-dose antioxidant supplements can have similar benefits to fruit and vegetables, especially during and after cancer, treatment is a controversial one.
There are concerns that supplements, especially antioxidants, could counteract the effects of chemotherapy or radiation therapy. Radiotherapy and certain types of chemotherapy are designed to increase the production of a type of free radical in the body called reactive oxygen species (ROS).
ROS can react with genes inside cells by creating structural bonds which can prove potentially fatal to cells. If the damage occurs to cancer cells, then that is bad news for cancer cells and good news for the person. Unfortunately, ROS action is not always selective, and many normal healthy cells succumb to ‘friendly fire’ from the cancer treatment.
Are antioxidants good or bad guys?
This is where the story gets complicated as theoretically, antioxidant supplementation could either increase or decrease the effectiveness of cancer treatment
In a new research study aimed at helping to answer the question on antioxidant supplements during cancer treatment, researchers collected supplement use habits of over 2,200 post-menopausal women who had undergone breast cancer treatment. Over a third of the women took supplements before and after their cancer diagnosis. Vitamin C, vitamin E, vitamin A, selenium, zinc and multivitamin supplements were the most common supplements taken.
After adjusting for potential factors that could bias the study, supplement use during chemotherapy or radiotherapy was linked to a 64 percent greater total mortality. An almost doubling in the rates of cancer recurrence was also seen in supplement users.
The study was observational so cannot prove that it was the antioxidants interfering with the cancer treatment. But the study results do not stand in isolation.
Already recommendations exist advising people undergoing cancer treatment to not take antioxidants. And this is based on previous intervention and observational studies with antioxidants during cancer treatment showing worse outcomes. For example, a
What it all means
During breast cancer treatment, the taking of antioxidants is a choice that should be closely discussed with treating medical staff. While there is evidence to show that antioxidants can reduce treatment-related side-effects, this appears to be at the expense of tumour recurrence rates and overall survival.
Michael Thomsen says
Research in this field is extremely important given the high level of supplementation in cancer patients.
However, it makes no sense to group all those herbal and nutritional supplements together as “antioxidants”.
I am not aware of any study that has been able to directly establish that a supplemental antioxidant interfered with chemoradiotherapy because it was an “antioxidant”. It remains a theoretical concern but in any case grouping such different compounds together and just referring to them as ‘antioxidants’ is meaningless.
Secondly, if the opposite had been true, that taking these compounds improved the prognosis, it would be dismissed as a unreliable results because patients are notoriously bad a remembering and recording dietary habits and supplement use, dosage, frequency etc.
In your review you also glance over the author’s caveats. I think they are so significant that one can not conclude from this study that ‘antioxidants’ or indeed those specific nutrients are associated with a worse prognosis.
And common sense would suggests that antioxidants are not an issue. Fruits, nuts, seeds and vegetables are full of antioxidants, if antioxidants were associated with a worse prognosis, should we recommend not eating fruits and vegetables?
I do however agree with not giving high dose of specific nutrients in isolation unless there is a very good rationale for its use and it is safe. Betacarotene seems to be problematic. A plant-based, low animal protein, wholesome diet is always going to be the best option.
Future research is vital. Rather than grouping all herbal and nutritional compounds together, the research needs to be focused on specific compounds and they need to be randomized trials, not just association studies like this one.
Here are the caveats from the study:
When interpreting our results, there are some caveats to consider. In analyses examining antioxidant use during chemotherapy or radiation therapy, there were few events, specifically deaths from breast cancer, and results warrant replication in larger data sets with more events of interest. Also, unlike studies in the United States (15,26), antioxidant use (20% of all participants)is uncommon in Germany. In order to achieve statistical power,it was necessary to combine the antioxidants together rather than examine their associations with prognosis individually even though dietary antioxidants encompass a myriad of chemical classes such as carotenoids and polyphenols that are vital fora multitude of biological reactions. We were moreover unable to ascertain frequency and dose of supplements used, so dose-response relations between individual supplements and prognosis could not be studied. Information on postdiagnosis dietary intake of antioxidants, which, alone or in combination with supplemental antioxidants during chemotherapy or radiationtherapy, could affect breast cancer prognosis, was also not collected. Postdiagnosis supplement use for the time period after breast cancer diagnosis was collected∼5 y after diagnosis, so there is potential for recall bias, which could result in both underestimation and overestimation of supplement use. This misclassification is likely to have been nondifferential, and wouldhave resulted in attenuated associations with prognosis (40).
Daniel Chan says
Great points there Micheal.. This is what happens sometimes, people try to find things to blame when there is a bad outcome.
When people die from cancer, It’s all because of the supplements, the water, the food, the air, its the cancer etc., but never the chemotherapy aka. poison? Hmmm seem very bias. In life nothing is 100% guaranteed success including cancer treatment.
Conclusion is take control of your own health early when you can so you have no regrets.