Why a healthy gut can reduce side effects and improve outcomes 

The trillions of commensal bacteria in and on our bodies have a significant influence, not only, on our overall wellbeing, but the level of side effects and the effectiveness of cancer treatments.

People on cancer treatments, ideally, should be making positive steps to protect their gut microbiome yet, 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 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 hence neutropenic infection.

Many cancer centres such as Memorial Sloane Kettering recommend lifestyle and nutritional strategies to improve gut health during chemotherapy such as increasing the intake of fermented foods such as kimchi, eating more fibres in beans, vegetables, mushrooms, eating more prebiotic phytochemicals, exercising more and reducing processed sugar intake..read more

yourgutOn top of these practical measures, a number of placebo-controlled randomised trials have also shown that 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 safe during chemotherapy – 85% of them revealed that probiotics reduced the incidence of treatment-related side effects in oncology patients. While 15% reported no impact in their findings, no study reported any harm… more

A word of caution with probiotics: 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 17.41.40People 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

Several well-conducted trials have demonstrated that probiotics can help prevent radiation bowel damage and aid recovery after radiotherapy...more .

gut health and probioticsThe gut microbiome is also implicated in cancer incidence is its influence on inflammation, oxidative stress, immune surveillance [Yadav]. 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]. Women with poor gut health have a higher percentage of mast cells in the breast tissue which encourage cancer cells to metastasise. 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:

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.