Probiotics, widely recognized for their role in gut health, have recently gained attention in cancer therapy. New evidence indicates that probiotics may boost the effectiveness of cancer treatments like immunotherapy while also minimizing the adverse side effects of chemotherapy and radiation.
The Role of Probiotics in Cancer Therapy
Probiotics are live microorganisms when ingested in adequate amounts, provide health benefits, primarily through modulation of the gut microbiota. Since the gut microbiome is closely linked to the immune system, its balance can greatly impact how the body responds to cancer treatments. Studies have shown that a diet rich in Lactobacillus is associated with a lower incidence of colon cancer.1 Probiotics have attracted interest for their ability to regulate cancer cell growth (proliferation) and death (apoptosis), offering a potential alternative to invasive treatments like chemotherapy or radiotherapy.2
Mechanisms of Action: How Probiotics Enhance Cancer Therapy
Probiotic bacteria play a crucial role in maintaining homeostasis by promoting stable physicochemical conditions in the colon. Probiotics may:
- Regulate pH Levels and Bile Acids: Lactobacillus acidophilus and Bifidobacterium bifidum help balance the body by regulating pH and bile acid levels in the gut. This can lower cancer risk and make these probiotics a valuable tool for cancer prevention.3
- Maintain Gut Bacterial Balance: Numerous studies have confirmed that probiotics positively influence the activity of bacterial enzymes linked to tumor development in humans.4
- Reduce Mutagenic Effects: Probiotics may bind to and break down carcinogens. Harmful compounds that increase colon cancer risk are often found in unhealthy foods, especially fried meats. Research has shown that consuming Lactobacillus strains reduces the mutagenic effects of a high-cooked-meat diet, leading to lower levels of heterocyclic aromatic amines in urine and feces.5
- Reduce Inflammation: Probiotics can either enhance or suppress the production of anti-inflammatory cytokines and regulate prostaglandin secretion, helping to prevent cancer development.6
- Suppress H. pylori and HPV Infections: Studies have shown that certain Lactobacillus strains can inhibit H. pylori infections, which are linked to gastric cancer.7 Additionally, research on patients with persistent human papillomavirus (HPV) revealed that daily probiotic intake over six months significantly improved the clearance of HPV and precursors to cervical cancer.8
- Improve Drug Metabolism: Some studies suggest that probiotics can affect the absorption and metabolism of certain cancer therapies, such as those for colorectal cancer, making treatments more effective.9
Promising Results from Recent Trials
Recent clinical trials have highlighted the potential benefits of probiotics in enhancing the effectiveness of cancer therapies while reducing side effects.
Probiotics to Reduce Chemotherapy-Induced Diarrhea: Chemotherapy often causes gastrointestinal distress, reducing patients’ quality of life and interrupting treatment. A study published in Frontiers in Nutrition explored the potential of oral probiotics to reduce chemotherapy-induced diarrhea and mucositis. This meta-analysis showed that orally administered probiotics could lower the incidence of chemotherapy-induced diarrhea and oral mucositis. However, more clinical trials are required to confirm the effectiveness of probiotics in managing these side effects, and the specific strains and dosages need to be standardized before clinical use.12
Probiotics Complementing Colorectal Cancer Treatment: Research indicates that next-generation probiotics (NGP) and postbiotics may help develop new treatments for colorectal cancer (CRC). These probiotics produce essential natural compounds and metabolites that enable new signaling between the host and microbiota to combat CRC. Although promising results have emerged, more research is needed to focus on specific strains and dosages to ensure the safety and effectiveness of traditional probiotics, NGP, and postbiotics in preventing and treating CRC.10
Probiotics and Vaginal Health: While the role of probiotics in female reproductive health is still debated, they are known to stabilize the vaginal environment, enhance immune defenses, and help prevent cervical cancer. Lactobacillus attaches to the vaginal lining and competes with harmful pathogens, preventing colonization. It also produces bacteriocin and hydrogen peroxide (H₂O₂), which inhibit harmful microorganisms and maintain the vagina’s low pH level.11
Challenges Ahead for Probiotics in Cancer Treatment
While many of the positive results from probiotic treatments have been observed in experimental studies, some microbes marketed as ‘probiotics’ in fermented foods lack clinical trial support. Additionally, certain probiotic strains may cause side effects, such as systemic infections, gene transfer, harmful metabolic activities, and overstimulating the immune system, especially in immunocompromised patients.13 Although research on the role of probiotics in cancer therapy is still in its early stages, recent trials are promising. However, more extensive studies are necessary to fully understand how probiotics interact with cancer therapies and to determine the best strains and dosages for different cancer types.
Ongoing clinical trials will likely provide further insights into how probiotics can be integrated into standard cancer treatments. In the near future, probiotics may become a routine part of cancer care, improving patient outcomes and reducing side effects.
Conclusion
The potential of probiotics in cancer therapy is an exciting and promising area of research. By influencing the gut microbiome, probiotics may enhance the effectiveness of cancer treatments like immunotherapy and reduce the side effects of chemotherapy and radiation. As more clinical trials are conducted, probiotics could become an essential part of cancer care, offering new hope to millions of patients worldwide.
References
- Goldin BR, Gorbach SL. Effect of Lactobacillus acidophilus dietary supplements on 1,2-dimethylhydrazine dihydrochloride-induced intestinal cancer in rats. J Natl Cancer Inst. 1980 Feb;64(2):263-5. doi: 10.1093/jnci/64.2.263. PMID: 6766509.
- Górska A, Przystupski D, Niemczura MJ, Kulbacka J. Probiotic Bacteria: A Promising Tool in Cancer Prevention and Therapy. Curr Microbiol. 2019 Aug;76(8):939-949. doi: 10.1007/s00284-019-01679-8. Epub 2019 Apr 4. PMID: 30949803; PMCID: PMC6586914.
- Jia W, Xie G, Jia W. Bile acid-microbiota crosstalk in gastrointestinal inflammation and carcinogenesis. Nat Rev Gastroenterol Hepatol. 2018 Feb;15(2):111-128. doi: 10.1038/nrgastro.2017.119. Epub 2017 Oct 11. PMID: 29018272; PMCID: PMC5899973.
- Kim DH, Jin YH. Intestinal bacterial beta-glucuronidase activity of patients with colon cancer. Arch Pharm Res. 2001 Dec;24(6):564-7. doi: 10.1007/BF02975166. PMID: 11794536.
- Hayatsu H, Hayatsu T. Suppressing effect of Lactobacillus casei administration on the urinary mutagenicity arising from ingestion of fried ground beef in the human. Cancer Lett. 1993 Sep 30;73(2-3):173-9. doi: 10.1016/0304-3835(93)90261-7. PMID: 8221630.
- Ivanov II, Honda K. Intestinal commensal microbes as immune modulators. Cell Host Microbe. 2012 Oct 18;12(4):496-508. doi: 10.1016/j.chom.2012.09.009. PMID: 23084918; PMCID: PMC3516493.
- Oh Y, Osato MS, Han X, Bennett G, Hong WK. Folk yoghurt kills Helicobacter pylori. J Appl Microbiol. 2002;93(6):1083-8. doi: 10.1046/j.1365-2672.2002.01779.x. PMID: 12452966.
- Verhoeven V, Renard N, Makar A, Van Royen P, Bogers JP, Lardon F, Peeters M, Baay M. Probiotics enhance the clearance of human papillomavirus-related cervical lesions: a prospective controlled pilot study. Eur J Cancer Prev. 2013 Jan;22(1):46-51. doi: 10.1097/CEJ.0b013e328355ed23. PMID: 22706167.