Supplements and Cancer
Supplements and Cancer
At one point or another, you may have seen the claims of various dietary supplement manufacturers such as: “Insurance for healthy ageing and DNA protection” or “Protects from the effects of everyday pollution and other environmental exposures” or “Supports healthy oestrogen activity and detoxification to preserve women’s breast health.”
When it sounds too good to be true, it probably is (too good to be true)
What is a dietary supplement? The World Cancer Research Federation [1] defines a dietary supplement as a product intended for ingestion that contains a ‘dietary ingredient’ intended to achieve levels of consumption of micronutrients or other food components beyond what is usually achievable through diet alone.
Supplements are regulated like other drugs – right? Wrong! In the United States, the FDA regulates both finished dietary supplement products and dietary ingredients BUT under a different set of regulations than those covering "conventional" foods and drug products [2]. The manufacturer is responsible for the safety and quality of their products. In the UK, supplements are required to be regulated as foods and are subject to the provisions of general food law, but not regulated and tested as a drug. The Food Standards Agency states to the manufacturer “It is your responsibility to ensure that food supplements you sell are safe for consumption” [3]. In most countries, supplements do not undergo the same rigorous testing criteria as drugs leaving a significant gap in understanding how a supplement may interact with cancer cells or with the various cancer treatments.
Can taking supplements prevent cancer? Unless you are nutrient deficient and your care team has prescribed a supplement, the answer is no. A commentary published in the Journal from the National Cancer Institute summarized several studies that focused on supplements and the possible prevention of cancer [4]. The results were basically the same – there is no evidence to support recommending supplements to prevent different cancers. Other professional organizations, including the World Cancer Research Federation, concluded that there is little to no scientific evidence that supplements reduce cancer risk.
Could supplements potentially do harm? Yes! Several antioxidant trials have actually reported increased risks with supplementation. The most prominent example, the antioxidant b-carotene possibly preventing lung cancer, was tested in two high-risk populations of heavy smokers and asbestos-exposed individuals. Individuals randomly assigned to b-carotene in the Beta-Carotene and Retinol Efficacy Trial (CARET) trial had a 39% increase in lung cancer incidence compared with those in the placebo arm [5].
Are there risks with taking supplements during treatment? Yes, there are definitely risks with taking supplements during your treatment. There can be drug-nutrient interactions. For example, some chemotherapy drugs share the same absorption channels as vitamins, minerals, and phytonutrients and in high doses (such as with a supplement) these nutrients can impact the absorption of the drugs. In addition, antioxidants may lessen the effects of radiation by reversing cell damage (radiation works by causing cell damage in the body). There is ongoing research focused on probiotic supplementation and immunotherapy as a recent study suggested melanoma patients were 70% less likely to respond to immunotherapy when taking probiotic supplements [4].
The bottom line is to aim to meet your nutritional needs through diet alone. Eating a varied diet of fruits, vegetables, whole grains, and lean sources of protein is the best way to get enough vitamins, minerals, and phytonutrients.
Most importantly, always speak to your care team about any herbs, supplements, minerals, or vitamins you are or thinking about taking.
August 2022
Ms Annette Goldberg has no disclosures to report.
References
[1] WCRF International. Do not use supplements for cancer prevention. World Cancer Research Fund International. Accessed August 22, 2022. https://www.wcrf.org/diet-activity-and-cancer/cancer-prevention-recommendations/do-not-use-supplements-for-cancer-prevention/
[2] Office of Dietary Supplement Programs. Dietary Supplements. US Food and Drug Administration. Accessed August 22, 2022. https://www.fda.gov/food/dietary-supplements
[3] Food Standards Agency. Food Supplements. Food Standards Agency. Accessed August 22, 2022. https://www.food.gov.uk/business-guidance/food-supplements
[4] Martinez ME, et al. Dietary Supplements and Cancer Prevention: Balancing Potential Benefits Against Proven Harms. J Natl Cancer Inst. 2012;104(10):732-739
[5] Goodman GE, et al. The Beta-Carotene and Retinol Efficacy Trial: incidence of lung cancer and cardiovascular disease mortality during 6-year follow-up after stopping beta-carotene and retinol supplements. J Natl Cancer Inst. 2004;96(23):1743-1750.