Why a healthy gut can reduce side effects and improve outcomes 

Enhancing and protecting the gut microbiome is one of the most important self-help strategies people can do during cancer treatments to reduce side effects and enhance effectiveness.  Despite the overwhelming body of evidence to support this, many patients are sadly still told by their oncology team to actually avoid fermented foods and probiotics – the opposite advice!

inflammation gutThe trillions of commensal bacteria in and on our bodies have a significant influence, not only, on our overall wellbeing, response to cancer treatments, chance of getting cancer in the first place or relapsing after surgery. This is thought to be via  its influence on inflammation, oxidative stress, immune surveillance [Yadav].  One study showed that women with poor gut health have a higher percentage of cells which encourage cancer cells to metastasise.  The trouble is, even if a person’s gut health is good before treatment, it takes a battering from drugs such as antibiotics, anti-indigestion remedies and steroids. Chemotherapy agents can damage to the gut lining directly and gut microbiome, contributing to symptoms such as indigestion, fatigue, “brain fog”, joint aches, nausea and diarrhoea, which if severe, this can lead to dehydration, concentration of the chemotherapy in the bloodstream leading to neutropenic infection and a high risk of peripheral neuropathy.The gut microbiome is also implicated in cancer incidence

How to help your gut?

Many cancer centres such as Memorial Sloane Kettering recommend a range of safe  lifestyle and nutritional strategies to improve gut health during chemotherapy, radiotherapy, hormone therapies and immunotherapies. These include

  • increasing the intake of fermented foods such as kimchi and kefir
  • stopping smoking and exercising more
  • eating more fibres in beans, vegetables, mushrooms,
  • eating more prebiotic phytochemicals,
  • trying to get a good nights sleep
  • reducing processed sugar intake..read more

yourgut

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The role for probiotics supplements

Chemotherapy: On top of these practical measures, a number of placebo-controlled randomised trials have also shown that certain lactobacillus probiotics capsules can further reduce chemotherapy induced diarrhoea particularly from fluorouracil and irinotecan agents although they are likely to help with others. A recent summary (systemic review) of 20 studies showed that lactobacillus probiotics are very safe during chemotherapy. In this review,  17 of the studies revealed that probiotics reduced the incidence of treatment-related side effects in oncology patients, whilst only 3  reported no impact in their findings – N0 study reported any harm… read more.  In particular lactobacillus during chemotherapy:

  • Reduced chemo brain
  • lowered the risk of neutropenia
  • prevented diarrhoea and gut issues

Not all probiotics are safe during cancer treatments. The safest varieties are lactobacillus, which also have the most evidence of benefit. Try to pick a blend which as been evaluate din medical studies so has a high level of quality assurance – For example yourgutplus.

Hormonal therapies such as tamoxifen, aromatase inhibitors in women and ADT in men can adversely affect gut health which in the longer term contributes to menopausal symptoms, metabolic syndrome, arthralgia, cognitive impairment and osteoporosis. Dietary measure to maintain or restore gut health would be very sensible and some studies are showing that probiotic supplements may have an additional role...more

Screen Shot 2017 02 22 at 17.41.40Immunotherapies: People with poor gut health receiving immunotherapies have an increased chances of toxicity including diarrhoea and pulmonary inflammation. Clinical trials  show that people with poor gut health have up to 40% lower chance these treatments working including for tumours such as glioblastoma, melanoma, lung, breast, bowel cancers and sarcomas… read more

Radiotherapy: Several well-conducted trials have demonstrated that probiotics can help prevent radiation bowel damage, oral mucosities, secondat candida infection and aid recovery after radiotherapy...more .

Prostate Cancer: Laboratory models have shown that altering the gut microbiome can slow prostate cancer (CaP) progression [Pernigoni]. In men with CaP, lower levels of gut lactobacillus strains have been linked with a higher rate of prostate cancer and biochemical recurrence [Kim]. Most importantly, a recent double blind RCT found that an intervention with the lactobacillus, inulin and vitamin D capsule called Yourgutplus significantly slowed CaP progression in men compared to placebo especially it combined with the supplement YourPhyto which contained 6 phytochemical rich foods [Thomas].


References:

Li et al `systemic review of probiotics and chemotherapy Journal of Advanced ResearchVolume 64, 2024, 223-235

Masaaki et  RCT neo-adjuvant chemotherapy oesophageal cancer Clinical Nutrition 36, 1, 2017, 93-99

Juan Z, et al. Probiotics reduce chemo-related cognitive impairment in women with breast cancer: a randomised, double-blind, placebo-controlled trial. Eur J Cancer. 2022 ;161:10-22.

Rodriguez-Arrastia M, et al Probiotic Supplements on Oncology Patients’ Treatment-Related Side Effects: A Systematic Review of Randomized Controlled Trials. Int J Environ Res Public Health. 2021 17;18(8):4265. doi: 10.3390/ijerph18084265. PMID: 33920572; PMCID: PMC8074215.

Feng TY, et al. Reciprocal Interactions Between the Gut Microbiome and Mammary Tissue Mast Cells Promote Metastatic Dissemination of HR+ Breast Tumours. Cancer Immunol Res. 2022 Nov 2;10(11):1309-1325. doi: 10.1158/2326-6066.CIR-21-1120. PMID: 36040846; PMCID: PMC9633553.

Pernigoni N et al. Commensal bacteria promote endocrine resistance in prostate cancer through androgen biosynthesis. Science. 2021 Oct 8; 374(6564):216-224. doi: 10.1126/science.abf8403. Epub 2021 Oct 7. PMID: 34618582.

Thomas R, Kenfiled S, Newton R et al.  Gut health and prostate cancer: The influence of a specific phytochemical-rich food capsule plus or minus a probiotic/prebiotic blend on symptoms and progression—A randomised, double-blind placebo-controlled trial. 2025. https://ascopubs.org/doi/10.1200/JCO.2025.43.5_suppl.311

Kim JH, et al. Biochemical Recurrence in Prostate Cancer Is Associated with the Composition of Lactobacillus: Microbiome Analysis of Prostatic Tissue. Int J Mol Sci. 2023 Jun 21;24(13):10423. doi: 10.3390/ijms241310423. PMID: 37445601; PMCID: PMC10341780.