We've seen cancer treatment for years focus on one thing.
The tumour.
Remove it. Burn it. Poison it. Starve it.
But in the last decade we've seen researchers begin to look elsewhere for clues about why some treatments work and others don't.
The tumour isn't the only issue.
Chemotherapy isn't the only issue.
The immune system working alone isn't the only issue.
The bacteria living in the gut.
This hidden world – known as the microbiome – is rapidly becoming a major new area of cancer research.
And it's creating a question for both doctors and patients.
Could the bacteria in your gut be influencing how effective your cancer treatment is?
The Cancer Microbiome in 30 Seconds
If you want the quick answer:
- There are trillions of microbes (the microbiome) in your gut.
- The microbiome interacts with your immune system.
- Some species of bacteria can affect how well you respond to immunotherapy.
- Antibiotics and chemotherapy can harm the balance of the microbiome.
- Fibre, fermented foods, and other healthy diet options may assist in maintaining a diverse microbiome.
The microbiome does not cure cancer.
But it may influence the environment in which the treatments work.
What is the Cancer Microbiome?
The term "cancer microbiome" describes the complex ecosystems of microorganisms that live in and on the human body and potentially impact cancer progression, immune response, and treatment efficacy.
There are approximately as many microbial cells in the human body as there are human cells, mostly living in the gastrointestinal system.
The collective group of microbes, including bacteria, fungi, viruses, and archaea, form the gut microbiome.
These microbes do not simply sit back and wait for events to happen; they affect several key processes in the body, including:
- Immune regulation
- Metabolism
- Inflammation
- Absorption of nutrients
- Neurological signalling
Therefore, researchers today think of the microbiome more like a metabolically active organ rather than a mere population of innocuous bacteria.
Due to this fact, the microbiome is viewed as a critical component in diseases like cancer.
The Gut – Immune System Relationship
Approximately 70% of the immune system resides in the gastrointestinal tract.
This implies that the microbiome is in constant contact with immune cells.
Some microbes induce immune responses.
Other microbes suppress inflammation.
Some help teach immune cells to recognise dangerous entities.
When the system is balanced, the immune system generally functions well.
When the microbiome is disrupted (dysbiosis), the immune system can either be hyper-responsive or hypo-responsive.
Either condition can affect the biology of cancer.
The Unexpected Relationship Between Gut Bacteria and Cancer Treatments
One of the most interesting discoveries in modern oncology research is that gut bacteria may affect how treatments perform.
Multiple studies have demonstrated that patients whose microbiome is more diverse may benefit from specific treatments, especially immunotherapy.
Immunotherapy stimulates the immune system to identify and destroy cancerous cells.
However, only a fraction of patients respond to these types of therapies.
Scientists attempting to solve this enigma determined that certain bacterial species seem to be present more frequently in patients who responded better to immunotherapy.
Microbes under investigation include:
• Akkermansia muciniphila
• Bifidobacterium species
• Faecalibacterium prausnitzii
These bacteria appear to modulate the immune signalling pathways involved in anti-tumour responses.
In essence:
A healthy microbiome can help facilitate immune system function.
Antibiotics and Cancer Treatment Efficacy
Research into the relationship between the microbiome and cancer treatment efficacy has revealed additional insights from research evaluating the use of antibiotics during cancer treatment.
Antibiotics can significantly alter the gut microbiome by killing a significant portion of the bacteria residing in the GI tract.
Studies have found that patients undergoing immunotherapy after being administered antibiotics may have lower levels of therapy efficacy.
This does not indicate that antibiotics are harmful to cancer patients.
They can be vital and life-saving when dealing with infections.
However, the results of these studies demonstrate how sensitive the microbiome may be during cancer treatment.
Chemotherapy and the Microbiome
Chemotherapy can also alter the gut microbiome.
Many chemotherapy agents kill rapidly dividing cells, including those in the lining of the GI tract.
These actions can alter the balance of the microbiome and lead to symptoms such as:
- Nausea
- Diarrhoea
- Inflammation
- Digestive problems
Researchers are currently studying the potential benefits of preserving the microbiome during treatment to enhance patient tolerance to treatment and post-recovery.
However, this field of study is still developing.
Personal Experience Supporting Gut Health During Treatment
I began focusing on supporting the underlying systems that treatment relies upon – particularly immune function and metabolism – after I was diagnosed with Stage IV Oesophageal Adenocarcinoma.
Chemotherapy and immunotherapy were two of the primary treatment options I pursued.
Supporting these underlying systems, however, was my interest in learning more about the microbiome.
Not because I thought probiotics or fermented foods were going to be the solution to curing cancer.
They aren’t.
But because the microbiome exists at the intersection of:
- Immunity
- Inflammation
- Metabolism
And those systems are crucial in the context of cancer treatment.
Therefore, in addition to my treatment I implemented practices that would support the diversity of my microbiome:
- Fermented foods
- Fibre intake
- Plant diversity
- Polyphenol-rich foods
All of these options support the biological environment in which treatment occurs.
Fermented Foods and Microbiome Diversity
Perhaps the simplest way to promote microbiome diversity is through the inclusion of fermented foods in your diet.
Examples of fermented foods include:
- Sauerkraut
- Kimchi
- Kefir
- Yogurt
- Fermented vegetables
Fermented foods introduce beneficial microbes and may promote increased microbiome diversity.
Studies have demonstrated that consuming fermented foods increases the diversity of the microbiome and reduces certain inflammatory biomarkers.
Fermentation jars or kits designed to simplify homemade fermentations can be purchased if you're interested in fermenting your own foods.
Fibre: The Microbiome's Favourite Food
Probiotics introduce beneficial microbes, and fibre feeds them.
Prebiotic fibres serve as the primary source of nutrition for beneficial gut bacteria.
As microbes digest fibre they create substances known as short-chain fatty acids (SCFA) that include butyrate.
Butyrate helps to:
- Reduce inflammation
- Maintain the integrity of the gut barrier
- Regulate immune cell signalling
The average Western diet contains relatively little fibre and this may partially account for the decreased diversity of the microbiome.
Increased fibre intake from whole foods is perhaps the simplest strategy to support the health of the microbiome.
Polyphenols: Feeding the Right Microbes
Plant-based compounds referred to as polyphenols also interact with the microbiome.
Examples of polyphenol-rich foods include:
- Berries
- Olive oil
- Green tea (especially Matcha)
- Dark chocolate (ideally 85%+)
- Herbs & Spices
Polyphenols may promote the proliferation of beneficial microbes and inhibit the proliferation of pathogenic microbes.
This is likely one explanation as to why diets containing a wide variety of plant-based foods may favourably influence the diversity of the microbiome.
What This DOESN'T MEAN
Every time microbiome research receives media attention, unsubstantiated claims inevitably follow.
It is therefore imperative to provide clarity on what the microbiome does not mean.
The microbiome does not:
- Probiotics Cure Cancer
- Fermented Foods Replace Cancer Treatment
- Bacteria in the Gut Determine Outcomes
Cancer biology is far too complex to be influenced by these simplistic statements.
However, the microbiome may represent one piece of the larger picture.
What Cancer Patients Can Do TODAY
While research into the relationship between the microbiome and cancer treatment continues to advance, there are several practical ways to support the health of the microbiome.
These are not cancer treatments.
However, they can support the biological systems that treatment relies on.
Strategies include:
- Eating a variety of plant-based foods
- Increasing fibre content in your diet
- Consuming fermented foods consistently
- Reducing ultra-processed foods
- Prioritising sleep and managing stress
These habits can support the health of the microbiome and the overall metabolic resilience of the individual.
Frequently Asked Questions Regarding the Cancer Microbiome
Can probiotics enhance cancer treatment?
Some studies indicate that certain probiotic strains may positively affect immune responses. Probiotics, however, are not cancer treatments and evidence is still in its infancy.
Will chemotherapy harm the good bacteria in the gut?
Chemotherapy can cause alterations to the microbiome and decrease the diversity of the microbiome, contributing todigestive issues during treatment.
Do antibiotics interfere with immunotherapy?
Some studies indicate that administering antibiotics before initiating immunotherapy may negatively affect the treatment efficacy of immunotherapy due to the disruption of beneficial bacteria.
Which foods support the health of the microbiome?
Foods associated with improved diversity of the microbiome include high-fibre vegetables, legumes, fermented foods, berries, olive oil, and other polyphenol-rich foods.
The Bottom Line
The microbiome will not cure cancer.
However, ignoring the microbiome may be unwise.
Microbes in our bodies are in continuous interaction with the immune system, generate chronic inflammation, and directly affect metabolic health.
Those systems all play roles during cancer treatment.
To me, the microbiome is not magic.
It is merely another component of the biological environment in which the body operates.
When dealing with something as severe as cancer, enhancing that environment wherever possible seems reasonable.
References
Routy B, Le Chatelier E, Derosa L, et al. Gut microbiome influences efficacy of PD-1–based immunotherapy against epithelial tumors. Science. 2018.
https://www.science.org/doi/10.1126/science.aan3706
Gopalakrishnan V, Spencer CN, Nezi L, et al. Gut microbiome modulates response to anti–PD-1 immunotherapy in melanoma patients. Science. 2018.
https://www.science.org/doi/10.1126/science.aan4236
Wastyk HC, Fragiadakis GK, Perelman D, et al. Gut microbiota-targeted diets modulate human immune status. Cell. 2021.
https://www.cell.com/cell/fulltext/S0092-8674(21)00754-6
Valdes AM, Walter J, Segal E, Spector TD. Role of the gut microbiota in nutrition and health. BMJ. 2018.
https://www.bmj.com/content/361/bmj.k2179
Schwabe RF, Jobin C. The microbiome and cancer. Nature Reviews Cancer. 2013.
https://www.nature.com/articles/nrc3610
Gopalakrishnan V, Helmink BA, Spencer CN, et al. The influence of the gut microbiome on cancer, immunity, and cancer immunotherapy. Cancer Cell. 2018.
https://www.cell.com/cancer-cell/fulltext/S1535-6108(18)30190-1
Matson V, Fessler J, Bao R, et al. The commensal microbiome is associated with anti–PD-1 efficacy in metastatic melanoma patients. Science. 2018.
https://www.science.org/doi/10.1126/science.aao3290
Turnbaugh PJ, Ley RE, Hamady M, et al. The human microbiome project. Nature. 2007.
https://www.nature.com/articles/nature06244
National Cancer Institute. Human Microbiome and Cancer.
https://www.cancer.gov/about-cancer/causes-prevention/risk/microbiome
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