Gut Microbiome Probiotics: A Hidden Ally in the Fight Against Cancer

Researched and written by Keith Bishop, Clinical Nutritionist, Cancer Coach, and Retired Pharmacist

My wife and I come from families with histories of cancer and dementia, and I was personally diagnosed with rheumatoid arthritis. As a teenager with acne, I took powerful antibiotics for years that contributed to loose stools. As I shifted my focus from traditional pharmacy to natural health and cancer support, I uncovered the crucial role of digestive health in tackling these health challenges. Since prioritizing my gut health, I’ve experienced a significant reduction in autoimmune aches and pains and tested negative for rheumatoid arthritis, transforming my overall well-being.

The gut microbiome, a vast ecosystem of trillions of microorganisms in our digestive tract, is emerging as a key player in cancer, health, and disease. Its influence extends beyond digestion, impacting immune function, mental health, and cancer prevention and treatment. Here's how this microscopic community can be a powerful ally in the fight against cancer.

Gut Microbiome and Cancer Risks

Research has shown that an imbalanced gut microbiome, or dysbiosis, can contribute to chronic inflammation, a known risk factor for cancer. Certain gut bacteria produce short-chain fatty acids (SCFAs), such as butyrate, which have anti-inflammatory and anti-cancer properties. By maintaining a healthy microbiome, we can potentially reduce the risk of cancers like colorectal cancer.[i]

Gut Microbiome and Cancer Cell Growth

The gut microbiome influences the tumor microenvironment, affecting cancer cell growth and progression.[ii] Beneficial bacteria can modulate immune responses, promoting the destruction of cancer cells while inhibiting tumor growth. This highlights the potential of targeting the microbiome as part of cancer therapy.[iii]

Supporting Cancer Treatments

Chemotherapy and Radiation Therapy: The gut microbiome can impact these treatments' efficacy and side effects. Certain bacteria enhance the body's ability to tolerate chemotherapy,[iv] while others help repair damage caused by radiation.[v]

Immunotherapy: Emerging evidence suggests that a diverse and balanced microbiome improves the effectiveness of immunotherapy by enhancing the immune system's ability to target cancer cells.[vi]

Gut Microbiome and Overall Health

Immune Function: The microbiome trains the immune system to recognize and combat harmful pathogens, reducing the risk of inflammation, infections,[vii] and autoimmune diseases.[viii]

Mental and Emotional Health: The gut-brain axis connects the microbiome to the brain, influencing mood, cognition, and emotional well-being. Probiotics have shown promise in alleviating symptoms of anxiety and depression.[ix] [x] [xi]

Stomach Acid and Gut Health

Sufficient stomach acid is essential for optimal digestion and maintaining a healthy gut microbiome. Gastric acid breaks down food into absorbable nutrients, creating an acidic environment that prevents harmful pathogens from entering the intestines.[xii] This acidity supports the growth of beneficial gut bacteria, which thrives in a balanced pH environment.[xiii] Low stomach acid, or hypochlorhydria, can lead to poor nutrient absorption, bacterial overgrowth, and an increased risk of gastrointestinal infections. Studies have highlighted the role of stomach acid in regulating gut microbiota composition and its impact on overall health. Maintaining adequate stomach acid levels through a balanced diet and lifestyle is crucial for digestive health and microbial harmony.

Check out the low stomach acid test guides in the learning center on our website.

The Role of Fermented Foods

Fermented foods are a natural way to support a healthy gut microbiome. They are rich in probiotics, replenishing beneficial bacteria and promoting microbial diversity.[xiv]

Homemade Yogurt: Super Gut Recipe - Combine milk with a yogurt starter culture like MyReuteri and ferment at a consistent temperature (around 100°F) for 36 hours. The result is a creamy, probiotic-rich treat. Refrigerate for storage.

How to make L. reuteri yogurt: An UPDATED step-by-step guide.

This links to Dr. William Davis’s book Super Gut on Amazon.

Note: Diary consumption, even yogurt, is associated with an increased risk of prostate cancer in men.[xv]

Homemade Sauerkraut: Shred cabbage mixed with salt and packed tightly into a jar. Allow it to ferment at room temperature for 1-4 weeks, depending on your taste preference. Refrigerate for storage.

Homemade Kimchi: Mix napa cabbage with garlic, ginger, chili flakes, and fish sauce. Ferment in a sealed jar for 3-7 days for a tangy, spicy probiotic boost. Refrigerate for storage.

Conclusion

The gut microbiome is a cornerstone of health, influencing everything from cancer risk to emotional well-being. By nurturing this hidden ecosystem through diet, lifestyle, and fermented foods, we can harness its power to support cancer prevention and treatment. As research continues to uncover the microbiome's secrets, its role in medicine will only grow.

Together – We Prevail Over Cancer!™ One Microbe at a Time.

[i] Sun, J., Chen, S., Zang, D., Sun, H., Sun, Y., & Chen, J. (2024). Butyrate as a promising therapeutic target in cancer: From pathogenesis to clinic (Review). International Journal of Oncology, 64, 44. https://doi.org/10.3892/ijo.2024.5632

[ii] Liu, C., Fu, L., Wang, Y. et al. Influence of the gut microbiota on immune cell interactions and cancer treatment. J Transl Med 22, 939 (2024). https://doi.org/10.1186/s12967-024-05709-3 +

[iii] Shalini, Ahana Majumdar, Rayees AK, Paheli Bhatt. Gut microbiome and cancer: Mechanisms, dysbiosis, and therapeutic prospects. J Curr Res Food Sci 2025;6(1):181-184. DOI: 10.22271/foodsci.2025.v6.i1c.199

[iv] Yang, S., Hao, S., Ye, H. et al. Crosstalk between gut microbiota and cancer chemotherapy: current status and trends. Discov Onc 15, 833 (2024). https://doi.org/10.1007/s12672-024-01704-8

[v] Liu, J., Liu, C. & Yue, J. Radiotherapy and the gut microbiome: facts and fiction. Radiat Oncol 16, 9 (2021). https://doi.org/10.1186/s13014-020-01735-9

[vi] Zhang, M., Liu, J. & Xia, Q. Role of gut microbiome in cancer immunotherapy: from predictive biomarker to therapeutic target. Exp Hematol Oncol 12, 84 (2023). https://doi.org/10.1186/s40164-023-00442-x

[vii] Ferrão, M., Muller, G. C., Campos, D. M., Peruzzo, J., Bonamigo, R. R., Veit, T., & Vianna, F. S. (2023). Role of gut microbiota in infectious and inflammatory diseases. Frontiers in Microbiology, 14, 1098386. https://doi.org/10.3389/fmicb.2023.1098386

[viii] Sadeghpour Heravi, F. Gut Microbiota and Autoimmune Diseases: Mechanisms, Treatment, Challenges, and Future Recommendations. Curr Clin Micro Rpt 11, 18–33 (2024). https://doi.org/10.1007/s40588-023-00213-

[ix] Gupt, A., Naudiyal, S., Rani, A. et al. Mental Health and the Microbiome: A Review of Psychological Impacts of Gut Microflora. Curr. Pharmacol. Rep. 10, 223–236 (2024). https://doi.org/10.1007/s40495-024-00357-z

[x] Merlo, G., Bachtel, G., & Sugden, S. G. (2024). Gut microbiota, nutrition, and mental health. Frontiers in Nutrition, 11, 1337889. https://doi.org/10.3389/fnut.2024.1337889

[xi] Arneth B. Gut-Brain Axis and Brain Microbiome Interactions from a Medical Perspective. Brain Sciences. 2025; 15(2):167. https://doi.org/10.3390/brainsci15020167

[xii] Beasley, D. E., Koltz, A. M., Lambert, J. E., Fierer, N., & Dunn, R. R. (2015). The Evolution of Stomach Acidity and Its Relevance to the Human Microbiome. PLOS ONE, 10(7), e0134116. https://doi.org/10.1371/journal.pone.0134116

[xiii] Biology Insights. Stomach pH: Mechanisms, variation, and microbial interplay. Biology Insights Website. Accessed March 20, 2025. Available from: https://biologyinsights.com/stomach-ph-mechanisms-variation-and-microbial-interplay/?form=MG0AV3

[xiv] Leeuwendaal NK, Stanton C, O’Toole PW, Beresford TP. Fermented Foods, Health and the Gut Microbiome. Nutrients. 2022; 14(7):1527. https://doi.org/10.3390/nu14071527

[xv] Alzahrani MA, Shakil Ahmad M, Alkhamees M, et al. Dietary protein intake and prostate cancer risk in adults: A systematic review and dose-response meta-analysis of prospective cohort studies. Complement Ther Med. 2022;70:102851. doi:10.1016/j.ctim.2022.102851 https://www.sciencedirect.com/science/article/pii/S096522992200053X?via%3Dihub