Written by: Dr. Adam McLeod, ND, BSc(Hons)
I frequently hear from patients that their Medical Doctor bluntly told them to forget changing their diet because it does not make a difference, even though this is not accurate based on a large body of scientific evidence. I was very surprised to hear a patient tell me that their doctor told them to specifically avoid blueberries. This was the only dietary recommendation that they were given.
When I asked why the doctor prescribed such a bizarre dietary change the patient replied that the antioxidants from blueberries can interfere with the chemotherapy and radiation. Although I was happy to hear that this doctor was offering dietary advice, unfortunately this advice is not accurate. There is no evidence to suggest that antioxidants from natural sources are dangerous during chemotherapy or radiation. In fact, virtually all of the literature clearly states the opposite which is that it is very beneficial to get antioxidants from natural sources. By consuming antioxidant rich foods patients have less side effects during chemotherapy and radiation. Many studies have also clearly demonstrated that these foods do not interfere with the effectiveness of these conventional therapies2,3,4,5,6,7.
It is interesting to note that of all the foods in the world this doctor only picked one item: blueberries. I am not sure of the rationale with this recommendation because there are countless foods that have antioxidant properties. Although blueberries are commonly associated with being antioxidants they are not very potent antioxidants when compared to other common foods. The antioxidant capacity of a food is measured by a lab test which determines the ability of that food to neutralize free radicals. This is commonly known as the Oxygen Radical Absorbance Capacity (ORAC) and a quick google search will clearly demonstrate that blueberries do not even make the top 50 for antioxidant capacity. These values are based on biological samples in vitro and it is not clear how significant these values are in the human body. What is clear, is that these values are a measure of the antioxidant capacity of these foods.
Depending on which source you look at blueberries have a ORAC value of approximately 6,500 which is not particularly high when compared to cinnamon which has an ORAC value of 265,000. In other words cinnamon is approximately 40 times stronger of an antioxidant compared to blueberries. Of course one could argue that you do not have as much cinnamon as blueberries, which is indeed true. However there are other foods consumed in comparable amounts to blueberries which have a significantly higher antioxidant capacity. Unsweetened cocoa powder has an ORAC value of 81,000 and baking chocolate has an ORAC value of 50,000. If you are having a food rich in chocolate then chances are you are consuming more antioxidants than if you are having blueberries1,8.
I am not suggesting that chocolate should be a primary source of antioxidants. I would certainly prefer that my patients get their antioxidants from blueberries rather than chocolate. There are many bioflavonoids in blueberries that are helpful in the context of cancer and the elevations in blood sugar from excessive chocolate consumption is not desirable in cancer patients. The point is that it is silly to single out one food as a antioxidant concern. The reality is that if you really want to cut antioxidants out of your diet it would involve much more than the elimination of blueberries. The advice of avoiding blueberries is confusing and it is simply not an evidence based dietary plan.
The bottom line is that these natural sources of antioxidants are very helpful in the context of cancer and there is no debate about this in the scientific community. The debate is around synthetic supplementation with high doses of antioxidants during chemotherapy and radiation. Natural sources are well established to be beneficial in these cases as they protect healthy cells without interfering with the effects of these conventional therapies5. So make sure you eat your blueberries and give your cells the nutrients that they need!
Blueberries are a great source of nutrients and they provide a balanced antioxidant support that is synergistic with chemotherapy and radiation. What is particularly interesting is that wild blueberries are much more effective at neutralizing free radicals when compared to cultivated blueberries. Depending on which measurements you use, in some cases the wild blueberries have almost double the antioxidant capacity!
If you are undergoing chemotherapy or radiation make sure that you contact a Naturopathic Doctor to develop an evidence based treatment plan that can support you through these therapies. During chemotherapy or radiation your cells are under a significant amount of stress and it is essential that you adequately supply your cells with the necessary nutrients. Diet is an important component of any integrative cancer therapy.
Dr. Adam McLeod is a Naturopathic Doctor (ND), BSc. (Hons) Molecular biology, Motivational Speaker and International Best Selling Author
His clinical focus is Naturopathic cancer care and he currently practices as at Yaletown Naturopathic Clinic in Vancouver, BC. https://www.yaletownnaturopathic.com
1) Haytowitz, David B., and Seema Bhagwat. “USDA database for the oxygen radical absorbance capacity (ORAC) of selected foods, Release 2.” US Department of Agriculture (2010).
2) Moss, Ralph W. “Should patients undergoing chemotherapy and radiotherapy be prescribed antioxidants?.” Integrative cancer therapies 5.1 (2006): 63-82.
3) Simone, Charles B., et al. “Antioxidants and other nutrients do not interfere with chemotherapy or radiation therapy and can increase kill and increase survival, part 1.” Alternative therapies in health and medicine 13.1 (2007): 22.
4) Drisko, Jeanne A., Julia Chapman, and Verda J. Hunter. “The use of antioxidant therapies during chemotherapy.” Gynecologic oncology 88.3 (2003): 434-439.
5) Moss, Ralph W. “Do antioxidants interfere with radiation therapy for cancer?.” Integrative cancer therapies 6.3 (2007): 281-292.
6) Conklin, Kenneth A. “Cancer chemotherapy and antioxidants.” The Journal of nutrition 134.11 (2004): 3201S-3204S.
7) Block, Keith I., et al. “Impact of antioxidant supplementation on chemotherapeutic toxicity: a systematic review of the evidence from randomized controlled trials.” International Journal of Cancer 123.6 (2008): 1227-1239.
8) Vertuani, Silvia, et al. “Evaluation of Antiradical Activity of Different Cocoa and Chocolate Products: Relation with Lipid and Protein Composition.” Journal of medicinal food 17.4 (2014): 512-516.