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Probiotic Supplements and Cancer Immunotherapy Treatment

What are probiotics?

Probiotics are bacteria that live inside our intestines, making up our gut microbiome. They can be found in supplements and in many foods, including yogurt, kefir and kombucha. A balanced and diversified gut microbiome is optimal since each microbe plays a different role in the body and can aid in healthy digestion [i]. In fact, scientists have discovered these intestinal microbes that make up the gut microbiome have a huge influence on our immune system. Although the general belief is that probiotics make your microbiome healthier, this may not be true for all patients with cancer.

Probiotics and Cancer Treatment

Current research exploring probiotic supplements and cancer immunotherapy treatment found that certain probiotic supplements may affect the success of immunotherapy. At the AACR 2019 Annual Meeting, Christine Spencer, PhD from MD Anderson presented research with data that taking probiotic supplements may reduce the response of cancer patients to immunotherapy, specifically melanoma patients treated with anti-PD-1 checkpoint inhibitors [ii]. The study tested fecal samples from 113 patients and tracked patients’ probiotic supplement use. Forty percent of these patients regularly used probiotic supplements.


  • Probiotic users had lower diversity in the gut microbiome. There was a 70% reduction in odds that the melanoma patients would respond favorably to cancer immunotherapy with anti-PD-1 checkpoint inhibitors [ii]
  • A low gut microbiome diversity was linked to poorer response to checkpoint inhibitor immunotherapy
  • The gut microbiome in patients with melanoma may be negatively influenced by probiotic supplements

Fiber May Be Key  

The study found that eating a fiber rich diet was linked to a better response to immunotherapy. A subset of 46 patients treated with anti-PD-1 immunotherapy were five times as likely to respond [iii]. Fiber is an essential part of a healthy diet. A fiber rich diet consists of whole grains, vegetables, fruits, legumes and nuts. The high fiber diet was positively associated with bacteria shown to communicate response to the anti-PD-1 treatment [iv]. However, diets high in added sugar and processed meat were negatively associated with the bacteria. These findings reveal that incorporating fiber in your diet can be beneficial and safer than taking probiotic supplements.

Overall, the results of this study suggest that doctors and patients with cancer should carefully consider the use of probiotic supplements [ii], although more research is needed in this area.

This research study was presented at the American Association for Cancer Research (AACR) Annual Meeting 2019, but the full journal has not yet been published for the public or reviewed by the American Society of Clinical Oncology. Findings are further described in the abstract.


[i] Investigating the Power of Bacteria. Retrieved from https://www.aicr.org/publications/newsletter/2014/124-winter/newsletter-investigating-the-power-of-bacteria.html

[ii] Probiotics Linked to Poorer Response to Cancer Immunotherapy in Skin Cancer Patients. Retrieved from  https://www.parkerici.org/2019/04/02/probiotics-linked-to-poorer-response-to-cancer-immunotherapy-in-skin-cancer-patients/

[iii] Dietary Factors Affecting Gut Microbiome May Influence Response to Immunotherapy in Melanoma Patients. Retrieved from https://www.aacr.org/Newsroom/Pages/News-Release-Detail.aspx?ItemID=1273

[iv] Christine N. Spencer, Vancheswaran Gopalakrishnan, Jennifer McQuade, Miles C. Andrews, Beth Helmink, M.A. Wadud Khan… Jennifer A. Wargo. (2019). The Gut Microbiome (GM) and immunotherapy response are influenced by host lifestyle factors. 2019 American Association for Cancer Research Annual Meeting Abstract. Retrieved from https://www.abstractsonline.com/pp8/#!/6812/presentation/4578

Sammy Troob

Sammy is a summer intern at Savor Health and currently a student at Cornell University. She is studying Nutritional Sciences in the school of Human Ecology and has a passion for nutrition and health. Through taking an array of health courses and volunteering at her local hospital, she also became interested in exploring global and public health. She enjoys creating plant-based food recipes with her sister to motivate others about how food can be delicious yet healthy and nutritious. In her free time, Sammy enjoys spending time with her family, playing tennis and traveling.

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