Can probiotics (probiotic supplements) reduce cancer risk?

Probiotics and Cancer Risk Reduction: Current Evidence

Based on the current evidence, probiotics cannot be recommended for cancer risk reduction as there is insufficient consistent clinical data supporting their effectiveness for this purpose. 1

Evidence Assessment

Guidelines on Probiotics and Cancer

The most recent and authoritative guidelines do not support using probiotics for cancer prevention:

• The 2021 ESPEN Clinical Nutrition in Cancer guideline explicitly states there is insufficient consistent clinical data to recommend probiotics, even for the more limited purpose of reducing radiation-induced diarrhea 1
• The 2017 ESPEN Guidelines on Nutrition in Cancer Patients similarly indicates insufficient evidence to recommend probiotics for radiation-induced diarrhea 1

Limited Evidence for Specific Applications

While probiotics are not recommended for general cancer prevention, there is some evidence for specific limited applications:

• Radiation therapy support: Some studies show probiotics may reduce acute toxicity during pelvic radiotherapy, including reduced incidence and severity of diarrhea and abdominal pain 1
• Microbiota modulation: The 2023 APAGE-APSDE guidelines suggest that for individuals with abnormal abundance of pathogenic microbes but negative colonoscopy, lifestyle modifications including probiotics might help improve enteric microbiota by reducing potentially harmful bacteria 1

Mechanisms and Research Status

Research on probiotics and cancer shows several potential mechanisms, but clinical evidence remains limited:

• Potential mechanisms include:

  • Modulation of immune responses 2, 3
  • Anti-inflammatory effects 4
  • Reduction of enzymes implicated in carcinogen generation 5
  • Binding of mutagens by intestinal bacteria 5
  • Antioxidant activity 2

• Current research limitations:

  • Most studies are laboratory-based or small clinical trials with substantial risk of bias 6
  • Significant heterogeneity in probiotic strains, dosing, and study designs 1
  • Lack of large-scale human clinical trials 3

Clinical Considerations and Cautions

When discussing probiotics with patients, important considerations include:

• Safety concerns: Probiotics should be used cautiously in immunocompromised patients, including those undergoing cancer treatment 1, 6
• Strain specificity: Different probiotic strains have different effects; not all probiotics are equal 1
• Adjunctive role: Probiotics might be considered as adjunctive therapy in specific situations (like radiation-induced diarrhea) but not as primary cancer prevention 4

Bottom Line

While laboratory and some small clinical studies suggest potential benefits of probiotics in cancer-related contexts, current clinical guidelines do not support recommending probiotics specifically for cancer prevention due to insufficient consistent evidence. Patients interested in microbiome health should focus on comprehensive dietary approaches including adequate fiber intake and limited animal protein and fat, with probiotics potentially being one component of this broader approach 1.