Key Points

  • This page is under construction.
  • Before using this therapy, consult your oncology team about interactions with other treatments and therapies. Also make sure this therapy is safe for use with any other medical conditions you may have.
  • Probiotics are living microorganisms (bacteria and some yeasts) that can support gut and immune health when consumed in sufficient numbers.
  • Examples of probiotic foods are yogurt, kefir, sauerkraut, tempeh and kimchi.
  • Probiotics may reduce treatment-related diarrhea during chemotherapy and radiation treatment.
  • Yogurt consumption reduced risk of conventional adenoma, especially adenomas with high malignant potential in men, with probiotics likely contributing to the effect.
  • Probiotics improved immune response and the intestinal microbial environment in colorectal cancer patients.
  • Used in several integrative programs and protocols and in traditional medical systems (Ayurveda and traditional Chinese medicine).


Laura Pole, RN, MSN, OCNS, BCCT Senior Researcher

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Nancy Hepp, MS, BCCT Project Manager

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Last updated July 28, 2021.

Probiotics, Prebiotics and Synbiotics

Probiotics are living microorganisms (bacteria and some yeasts) that, when consumed in sufficient numbers, can provide health benefits that go beyond basic nutrition, such as supporting gut and immune health and keeping the gut microbiota in balance. Examples of probiotic foods are yogurt, kefir, sauerkraut, tempeh and kimchi. Probiotics are typically consumed in foods such as yogurt and other fermented foods. The effects of probiotic supplements separate from dietary sources are not always reported in the scientific literature. 

Prebiotics are dietary fibers that feed the friendly bacteria in your gut. Most prebiotics are soluble fiber substances like inulin, found in chicory root and foods like bananas, onions, jerusalem artichokes, jicama, garlic and others. Some supplements are also used as prebiotics, such as larch arabinogalactan (Web MD).

Your helpful bacteria turn inulin and other fibers into energy for the colon cells and create protective immunity. Inulin is increasingly being added to a number of processed foods and probiotic supplements. 

Synbiotics simply means consuming both prebiotics and probiotics together.

The evidence for taking probiotic supplements is mixed, with benefit so far mostly among people undergoing colorectal cancer surgery.

Clinical Practice Guidelines

The Society for Integrative Oncology’s 2009 guidelines on botanicals cite research indicating that probiotics are useful in reducing enteritis related to radiation therapy and Fluorouracil (5-FU), as well as reducing diarrhea induced by 5-FU and Irinotecan.1

Treating the Cancer

Working against cancer growth or spread, improving survival, or working with other treatments or therapies to improve their anticancer action

See cautions (below) about possible interference of probiotics with immune checkpoint inhibitors.

Lab and Animal Evidence

  • Anticancer and antimutagenic activity in animals, protecting against harmful effects of procarcinogens2
  • Suppressed colon tumor incidence/number and size and increased cell death (apoptosis) in animals3
  • May enhance the effectiveness of some cytotoxic and immune therapies4

Optimizing Your Terrain

  • Improved immune response5
  • Glycemia:
    • Lower fasting blood sugar, insulin, and homeostasis model assessment for insulin resistance (HOMA-IR) index among women with polycystic ovarian syndrome with pro-/synbiotic supplementation in a meta-analysis of RCTs6
    • Increased insulin sensitivity and insulin, plus decreased BMI, weight and waist circumference, in women with polycystic ovarian syndrome drinking a beverage supplemented with synbiotics compared to an unsupplemented beverage or controls in a small RCT7  
  • Microbiome balance:
    • Use of probiotics around the time of surgery improved the gut microbiome of people undergoing colorectal cancer surgery.8
    • Adding food enriched with prebiotics may possibly improve the condition of your microbiome, as shown in preliminary clinical studies.9
    • Lowered the gut pH10
  • Inflammation:
    • Lower C-reactive protein (a marker of inflammation) among women with polycystic ovarian syndrome with pro-/synbiotic supplementation in a meta-analysis of RCTs11
  • Hormone balance:
    • Lower total testosterone among women with polycystic ovarian syndrome with pro-/synbiotic supplementation in a meta-analysis of RCTs12
    • Lower testosterone in women with polycystic ovarian syndrome drinking a beverage supplemented with synbiotics compared to an unsupplemented beverage or controls in a small RCT13  

The prebiotic inulin is increasingly being added to a number of processed foods and probiotic supplements. Using inulin supplements may possibly improve the condition of your microbiome, although the evidence is not strong yet but is growing.14

Managing Side Effects and Promoting Wellness

Managing or relieving side effects or symptoms, reducing treatment toxicity, supporting quality of life or promoting general well-being

  • During chemotherapy and radiation treatment, probiotics may reduce treatment-related diarrhea.15
  • Colorectal cancer:
    • Reduced incidence of diarrhea induced by chemoradiotherapy, especially grade 2 or higher16
    • Reduced the portion of colorectal cancer patients experiencing irritable bowel symptoms or symptoms of depression, and  improved function-related quality of life and cancer-related quality of life scores in a small trial17
    • Conflicting findings on whether the use of  prebiotics, probiotics or synbiotics at the time of surgery in patients undergoing colorectal cancer surgery reduces the development of infectious complications18
    • Improved quality of life and chemotherapy-related side effects including appetite lossfatigue, painnausea and vomiting and diarrhea with a combination omega-3 fatty acid and strain-specific probiotic19

Reducing Risk

Reducing the risk of developing cancer or the risk of recurrence

Clinical Evidence

  • Yogurt consumption reduced risk of conventional colorectal adenoma, especially adenomas with high malignant potential, in men. Probiotics in yogurt are thought to contribute to this effect.20
  • Preliminary but mixed evidence that probiotic therapy may decrease the risk of developing colorectal cancer21 with different effects from different species22

Lab and Animal Evidence

  • Lactobacillus casei BL23 protected mice against colorectal cancer development.23


People with melanoma taking over-the-counter probiotic supplements before treatment had lower diversity of gut microbes and a 70% lower chance of response to cancer immunotherapy treatment with anti-PD-1 checkpoint inhibitors.24 Our comments on this:

  • It’s not clear whether people who were taking the supplements had experienced events that altered their microbiome—such as recent antibiotic use—and were working to re-balance it with probiotics. People taking antibiotics before treatment also had lower microbe diversity. If people taking probiotics also had altered microbe balanaces, then we don’t know whether the probiotics themselves or the underlying imbalance was the real culprit in the reduced response to immunotherapy.
  • We also don’t know how probiotic use in this study related to the food choices that promote a healthy microbiome. 
  • Until we can answer questions such as these, we caution against assuming that probiotic use is linked to poor treatment response. In the meantime, we urge caution in using probiotics before immunotherapy.

Neil McKinney, ND, and Lise Alschuler, ND, FABNO, do not give probiotics if the absolute neutrophil count is 1.5 or less.2526

BCCT advises consulting your physician before taking probiotic supplements. It may also be a good idea to work with a healthcare provider experienced in using probiotics in people with cancer, as many different types of probiotics are available, and taking the appropriate probiotic for your particular situation is important.

The About Herbs summary on Probiotics lists contraindications to taking probiotics as well as adverse events and herb-drug interactions.


BCCT does not recommend therapies or doses, but only provides information for patients and providers to consider as part of a complete treatment plan. Patients should discuss therapies with their physicians, as contraindications, interactions and side effects must be evaluated.

Dosage recommendations are available from these sources:

Integrative Programs, Protocols and Medical Systems

For more information about programs and protocols, see our Integrative Programs and Protocols page.
  • Programs and protocols
    • Alschuler & Gazella complementary approaches:27
      • Post-operative support
      • Bladder cancer
      • Breast cancer
      • Colorectal cancer
      • Gastric cancer
      • Pancreatic cancer (to reduce infection risk after Whipple procedure)
      • Healthy digestion
      • Hormone balance
      • Immune enhancement
      • Anti-inflammatory support
      • Insulin-resistance reversal
      • Managing diarrhea
      • Enhancing immune activity
      • Reducing inflammation and systemic inflammatory diseases
      • Reducing anxiety and depression
      • Improving insulin sensitivity
      • Improving digestion and detoxification
      • Reducing cancer risk
      • Reducing risk of dysbiosis from antibiotics
      • Colorectal cancer
    • Block program28
      • Core diet plan
      • Preventing/managing diarrhea from antibiotics
      • Radiation-induced enteritis
      • High-intensity nutritional support diet for cachexia (wasting)
    • Lemole, Mehta & McKee colorectal cancer protocol29
    • McKinney protocols30
      • Post-op diarrhea
      • With radiation therapy to protect gut and immune competence
      • Treatment-related diarrhea
      • With platin drugs (such as cisplatin) to prevent gut bacteria translocation to liver/blood
      • Protocol for better nutrition
      • Side effect alleviation protocol
      • Health restoration and creating healing conditions—detoxification
      • Cancer risk reduction plan
      • Reducing dysbiosis risk from antibiotics
      • Breast cancer
      • Colorectal cancer
  • Traditional systems

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