Gut Feelings: Current Research on The Role of The Microbiome in Cancer

May 15, 2023

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What is the gut microbiome?

Your gut contains more than 1 trillion microorganisms, including bacteria, viruses, archaea, and eukaryotes that live in your small intestine. These tiny organisms are often thought of as bad, but they actually do a lot of good things for your body. In fact, they have a special relationship with us where we both help each other out. This is called a symbiotic relationship.

Some functions of the gut microbiome include:

• Aiding in digestion and absorption of nutrients
• Preventing the proliferation of “bad” bacteria
• Aiding in metabolism of nutrients
• Synthesis of vitamins such as Vitamin K and certain B vitamins
• Synthesis of serotonin, GABA, and other neurotransmitters that affect mood, memory and cognitive function
• Regulating allergy and immune function
• Many, many others

What is Dysbiosis?

Dysbiosis is a condition where the balance of microorganisms in the gut is disrupted, often caused by various environmental and genetic factors. Additionally, as we age, the likelihood of developing gut dysbiosis increases. This imbalance can lead to negative impacts on overall health, including an increase in inflammation in the body. Inflammation is linked to the formation of various types of cancer, highlighting the importance of maintaining a healthy balance of microorganisms in the gut.

Does Dysbiosis in the Gut Microbiome Affect Cancer Treatment?

A recent review published in Gut suggests that knowing the certain kinds of bacteria we have in our gut might be able to tell us how well cancer treatments will work. For example, higher amounts of the bacteria Faecalibacterium and other Firmicutes, a type of bacteria that helps us digest food, are associated with longer survival in multiple myeloma patients on a certain immune checkpoint inhibitor.  However, an increase in Faecalibacterium was also shown to raise the risk of a side effect called colitis, or inflammation of the colon, that occurs in response to some cancer treatments. Alternatively, patients with reduced levels of Akkermansia muciniphila were less likely to respond to anti-PD-1, which is another type of cancer treatment. In contrast, patients who responded well to anti-PD-1 treatment had a higher diversity, meaning more species, of gut bacteria and enriched levels of Ruminococcaceae and Faecalibacterium, which are associated with better immune function in the environment created around a cancer tumor.

Two studies conducted by MD Anderson Cancer Center in 2022 revealed patients who survived longer after treatment with immune checkpoint inhibitors showed unique gut microbiome signatures, or common communities of microbes, compared to those who had shorter survival. While the study initially intended to examine the efficacy of immune checkpoint inhibitor therapy in glioblastoma patients, they also collected stool samples from patients as part of the study before and after treatment. They analyzed the gut microbiome composition and compared the results based on patient survival rates. The analysis revealed that increased numbers of Ruminococcus spp. were related to increased odds of survival and increased levels of Eubacterium spp. increased response to treatment. As a result of this exciting, yet unexpected, discovery, many clinical trials on glioblastoma now routinely collect stool samples from study participants. These findings highlight the importance of the gut microbiome in cancer treatment and may drive research on targeted therapies based on microbiome characteristics in the future.

Although this research is crucial for advancing cancer treatment, the study of the gut microbiome is a relatively recent area of investigation, and more research is needed to fully understand the complex relationship between the microbiome and cancer development and treatment. There are many ongoing clinical trials currently recruiting to uncover the role of the microbiome in cancer treatment (e.g. 1,2). For more information on open trials currently recruiting, sign up for OncoPower, and our team can help match you to a clinical trial, absolutely free!

What You Can Do to Support Your Gut During Treatment

Consume High Fiber and Fermented Foods

Many kinds of cancer therapies can harm the gut lining, making it essential to support your microbiome throughout the treatment process. Consuming a well-balanced diet rich in fiber, fruits, and vegetables can aid in feeding beneficial bacteria and improving microbial diversity in the gut. While cancer treatment might impact your appetite, do your best to consume these foods when you can!

Fiber is important for feeding the beneficial bacteria in the gut microbiome to keep out the bad bacteria, but it also functions to support regular bowel movements, control blood sugar levels, and help maintain a healthy weight. Some high-fiber foods include oats, quinoa, black beans, lentils, chickpeas, broccoli, brussels sprouts, kale, chia seeds, flaxseeds, prunes, and figs. Generally, fiber is considered beneficial for most individuals, including cancer patients. However, there are certain types of cancers and situations in which the amount of fiber recommended may need to be lowered including digestive complications, malnutrition, bowel obstruction or blockage, and after certain surgical procedures. Check with your care team for recommendations on how much fiber to include in your diet during treatment.

Additionally, fermented foods, also known as probiotic foods, are excellent sources of beneficial bacteria and can help replenish your microbiome after a round of antibiotics or during treatments that may harm your gut bacteria. Examples of probiotic foods include yogurt, sauerkraut, kefir, kimchi, kombucha, and tempeh. 

While taking on fermented food projects at home is fun, make sure to consume only commercially available fermented foods instead of farmer’s markets or homemade fermented foods while you are going through treatment. This is because it’s important to practice food safety while the immune system is compromised. Without the precise combination of ingredients and careful practice in making fermented food, bad bacteria might outcompete the good bacteria which could lead to illness for immunocompromised individuals. 

For patients who are experiencing digestive issues, probiotic foods might make negative symptoms, like nausea and diarrhea, worse. It’s important to assess your individual tolerance for fermented foods and work with a dietitian to assess whether adding these foods to your diet would benefit you. 

Overall, fermented foods can be a beneficial component of a healthy diet for cancer patients, but it is essential to assess your personal situation and consult your team of healthcare professionals. Your healthcare team can provide guidance on what is suitable for your specific situation and help you make informed decisions about your diet during cancer treatment.

Should You Take a Probiotic?

Over the past decade, probiotics have become increasingly popular among the general population. Although their benefits and effectiveness are still being studied, research suggests that probiotics may improve the diversity of the microbiome, as well as the efficacy of cancer treatments involving immunotherapy. Despite ongoing research, there is still much to learn about the full range of benefits that probiotics may offer in the oncology space.

One scientific review of clinical trials published by the National Institute of Health found that in cancer patients, probiotics can help reduce the negative side effects of chemotherapy and radiation therapy by improving bacterial diversity in the gut. Probiotics also produce helpful substances that fight against harmful bacteria and block their attachment to the intestinal walls. Some studies have found that probiotics can improve immune responses, reduce infectious complications, and even have positive effects on behavioral and cognitive symptoms in cancer patients. More specifically, one study found a positive link between the strain Bifidobacterium longum 1714 and decreased stress reduction and improved memory. Furthermore, a 2019 review reported on a study that linked oral intake of Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 to a decrease in depression symptoms in individuals with major depressive disorder. 

In addition, probiotics have been found to have neuroprotective and cardioprotective effects in both animal models and humans. In rat models, a combination of the strains Bifidobacterium breve, Lactobacillus casei, Lactobacillus bulgaricus, and Lactobacillus acidophilus was linked to a reduction in oxidative stress in a myocardial infarction model. 

 While exciting research is underway to understand the role of probiotic supplements in improving cancer treatment, many commercially available probiotics are not regulated by the FDA and contain a very limited number of bacteria that may not produce a health-altering response. Talk to your doctor or dietitian before taking any new supplements during treatment and they can help in selecting the most appropriate one for your condition and health goals. 

Join the community at OncoPower to speak with our Registered Dietitians who can help you learn more about how gut health can impact your cancer treatment.