Exploring the Gut Microbiome's Role in Integrative Oncology and Cancer Treatment

This is the area I am most excited and most energised to talk about right now. The science is evolving quickly, and its implications for people going through cancer treatment are genuinely significant.

What Is the Gut Microbiome?

Your gut microbiome is the vast community of trillions of microorganisms; bacteria, fungi, viruses, and other microbes, living primarily in your large intestine. Far from passive passengers, these microbes actively participate in immune function, inflammation regulation, hormone metabolism, and neurological health.

We each carry a unique microbial fingerprint, shaped by diet, lifestyle, medication history, stress, and early-life exposures — and the composition and diversity of this ecosystem has a direct bearing on cancer treatment outcomes.

The Microbiome–Immunotherapy Connection

The strongest evidence linking the gut microbiome to cancer treatment centres on immunotherapy — specifically checkpoint inhibitors such as anti-PD-1 and anti-CTLA-4, now standard of care across melanoma, lung, kidney, and other cancers. Three findings stand out:

• Melanoma patients responding to anti-PD-1 therapy showed distinct microbiome profiles from non-responders, with higher levels of Faecalibacterium prausnitzii and Akkermansia muciniphila (Science, 2018)

• Greater microbiome diversity correlated with improved progression-free survival on checkpoint inhibitors (MD Anderson)

• Recent antibiotic use, which disrupts the microbiome, was associated with significantly reduced immunotherapy response rates

The mechanism proposed to explain this is clear: a diverse, healthy microbiome helps prime and train the immune system, supporting the kind of robust immune activation that allows immunotherapy to work more effectively.

Chemotherapy, Side Effects & the Gut

Chemotherapy is also profoundly disruptive to the gut microbiome — damaging the gut lining and contributing to mucositis, diarrhoea, systemic inflammation, fatigue, cognitive changes, and increased infection risk. Encouragingly, early evidence suggests that targeted microbiome support before, during, and after treatment may reduce these side effects and aid recovery; Lactobacillus rhamnosus GG, for instance, has shown clinical promise specifically for chemotherapy-induced diarrhoea.

Akkermansia muciniphila: A Microbe Worth Knowing

Akkermansia muciniphila, a bacterium residing in the gut's mucus layer, has emerged as particularly significant in oncology. It supports gut barrier integrity, modulates immune responses toward anti-tumour activity, and critically seems to enhance checkpoint inhibitor response. Institut Gustave Roussy studies showed that patients with higher Akkermansia levels had better outcomes on anti-PD-1 therapy; FMT experiments in germ-free mice replicated this effect, pointing toward causation.

Polyphenols (berries, dark chocolate, green tea, olive oil) and prebiotic fibres (chicory, Jerusalem artichoke, garlic, onion) are among the most reliable dietary levers for raising Akkermansia levels.

Faecal Microbiota Transplantation (FMT) in Oncology

Faecal Microbiota Transplantation (FMT) involves transferring gut microbiome material from a healthy donor into a patient to restore microbial balance. This innovative approach is gaining attention in oncology as a potential way to enhance cancer treatment outcomes.

Recent early-phase clinical trials, published in Science (2021), demonstrated that FMT from immunotherapy responders to non-responders could restore sensitivity to treatment in some patients. These findings suggest that the gut microbiome may play a pivotal role in determining the effectiveness of immunotherapy.

The implications are profound: if immunotherapy response can be influenced by modifying the microbiome, FMT could become a valuable tool in personalizing cancer treatment. However, more research is needed to fully understand its mechanisms and to establish standardized protocols for its use in oncology.

What Can You Do? Practical Nutrition Strategies to Support Your Microbiome

The encouraging news is that diet is one of the most powerful levers we have to shape the gut microbiome — and change can happen relatively quickly. Here is what the evidence supports:

1. Prioritise Dietary Diversity

The single strongest predictor of a healthy microbiome is the diversity of plants in your diet. Research from the American Gut Project found that people who ate 30 or more different plant foods per week had significantly more diverse microbiomes than those eating fewer than 10. This includes vegetables, fruits, wholegrains, legumes, nuts, seeds, herbs, and spices — every variety counts.

2. Eat Plenty of Prebiotic Fibre

Prebiotics are the foods that beneficial bacteria feed on. Rich sources include:

• Garlic, onion, leeks, and shallots

• Jerusalem artichokes and chicory root

• Asparagus (particularly timely in June)

• Oats and barley

• Under-ripe bananas

• Cooked and cooled potatoes and rice (which form resistant starch)

  

3. Include Fermented Foods Daily

A 2021 Stanford study published in Cell demonstrated that a diet high in fermented foods significantly increased microbiome diversity and reduced inflammatory markers — including in cancer-relevant immune pathways. Aim to include:

• Live yoghurt (unsweetened)

• Kefir

• Sauerkraut and kimchi

• Miso

• Kombucha (low sugar varieties)

  
  

4. Eat a Rainbow of Polyphenol-Rich Foods

Polyphenols selectively feed beneficial bacteria including Akkermansia and Bifidobacterium. June's seasonal produce is particularly polyphenol-rich — strawberries, cherries, watercress, and beetroot are all excellent sources.

5. Limit Ultra-Processed Foods

Ultra-processed foods (UPFs) — those containing emulsifiers, artificial sweeteners, preservatives, and refined starches — have been shown to disrupt the gut lining and reduce microbial diversity. Even modest reductions in UPF intake can have measurable microbiome benefits.

6. Be Mindful of Antibiotic Use

Where clinically necessary, antibiotics are of course essential — but it is worth discussing with your oncology team whether the timing of antibiotic use can be considered alongside immunotherapy scheduling. Following any course of antibiotics, targeted probiotic and prebiotic support becomes especially important.

A Note on Probiotic Supplements

Probiotic supplementation during cancer treatment is an evolving and nuanced area. Some strains show real clinical promise; others are poorly evidenced. I would not recommend self-prescribing probiotic supplements during active treatment without personalised guidance — certain situations, including immunosuppression, require careful consideration. Please reach out if you'd like tailored advice.