The human gastrointestinal (GI) tract contains an abundant and diverse microbial community that gathers more than 100 trillion microorganisms. Gut bacteria are key regulators of digestion along the gastrointestinal tract; commensal bacteria play an important role in the extraction, synthesis, and absorption of many nutrients and metabolites, including bile acids, lipids, amino acids, vitamins, and short-chain fatty acids (SCFAs). Gut microbiota have a crucial immune function.

Gut microbiota have a crucial immune function against pathogenic bacteria colonisation inhibiting their growth, consuming available nutrients and/or producing bacteriocins. Gut microbiota also prevent bacteria invasion by maintaining the intestinal epithelium integrity.

The normal gut microbiota imparts specific function in host nutrient metabolism, xenobiotic and drug metabolism, maintenance of structural integrity of the gut mucosal barrier, immunomodulation and protection against pathogens. Strong evidence is emerging to support the effects of the gut microbiome on the development of some malignancies but also on responses to cancer therapies, most notably, immune checkpoint inhibition (immunotherapy). Tools for manipulating the gut microbiome including dietary modification, probiotics and faecal microbiota transfer (FMT).

The gut microbiome has been referred to as “the last undiscovered human organ”; microbes within the human gut have significant effects on human health and immune function due to their proximity to the immune environment within the gastrointestinal tract. Complex interactions allow for the oral tolerance of commensal bacteria and food antigens, along with enabling the immune system to recognise and attack opportunistic bacteria. In addition to influencing localised immune responses, the microbiota also has broader effects contributing to innate and adaptive immunity by modulating the regulatory phenotype of gastrointestinal dendritic cells [3]. This concept is supported in animal models: germ-free mice lacking intestinal microbiota are noted to have severe defects in immunity, with an absent mucous layer, altered IgA secretion and reduced size and functionality of Peyer’s patches and draining mesenteric lymph nodes.

Lower gut bacterial diversity has been observed in people with a wide range of conditions, including obesity, cardiovascular disease, autoimmune disease and neurological disorders, along with vaccine responses, suggesting a direct relationship between gut microbiome diversity and functional outcomes. Disruption of the delicate balance of commensal bacteria is seen in the setting of what is often referred to as dysbiosis, a somewhat ill-defined state characterised by a less diverse and less stable microbiota, with potential enrichment of opportunistic pathogenic bacteria. Such an imbalance can lead to impaired local, locoregional and systemic immune responses through the breakdown of mucosal barriers, alterations in cytokine signalling, inhibition of probiotic commensal bacterial colonisation and proliferation of enteropathogens. This results in the translocation of gut bacteria into the mesenteric lymph nodes and peripheral circulation, resulting in the activation of Th17 and effector T cells promoting neutrophil infiltration, and activation of an inflammatory phenotype both locally and systemically.

Probiotics and probiotics = synbiotics 
Probiotics are live bacteria that are thought to provide health benefits and aid in gut microbiome homeostasis, while synbiotics are a combination of prebiotics and probiotics in a single formulation. Some difficulties have been shown to exist in the transportation of live bacteria beyond the acidic environment of the upper GI tract, but efforts are underway to combat this. Symbiosis is the mutually beneficial relationship between certain nutrients and the biota (bacteria) that populate our bodies. When balanced, this relationship enables optimal immune and digestive health Probiotics are healthy bacteria that we introduce into our microbiome, or digestive system, to boost the healthy bacteria that already lives there. Probiotics can be found naturally in foods like Greek yoghurt, cheese, kimchi, and pickles; they also exist in supplement and powder form. Taking probiotics can boost some of the healthy bacteria already in your gut, which works at its best when it has a balance of “good” and “bad” bacteria. A balanced gut is an important part of your body’s overall wellness.

Evidence shows that probiotics can help with long-term symptom management for cancer patients following treatment, including chemotherapy-related diarrhoea. A 2014 study investigating the effects of administering probiotics to colorectal cancer survivors for 12 weeks saw a significant decrease in symptoms for patients suffering from irritable bowel symptom, ultimately improving quality of life for those patients. Another randomised trial, conducted with 150 patients, found that patients who underwent chemotherapy and received probiotics experienced significantly less grade three and four diarrhoea and also required fewer hospitalisations and dose reductions due to bowel toxicity. However, this group also had a higher number of neutropenia complications — meaning a lower-than-normal number of neutrophils, a type of white blood cell, in the blood. This can result in an infection.

In addition to alleviating symptoms of diarrhoea, probiotics can be beneficial for some cancer patients who have preexisting health problems such as irritable bowel syndrome and those experiencing other gastrointestinal issues like constipation, gas, or bloating, 

Probiotics are not the only way to maintain a healthy gut or to improve gastrointestinal problems. Fibre from fruits and vegetables, nuts, and whole grain foods can maintain and improve overall gut health. Gastrointestinal issues that patients may experience, such as gas, can also be chocked up to beverages such as soda, so switching your source of hydration can be helpful.

At Vitawell Wellness we recommend that these patients regularly change the types of probiotics they consume to get the benefit of a variety of probiotic strains.