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With the current climate it is important that we understand the relationship between the gut and aspect of our health. As modern research keeps unraveling the importance of microbial ecosystems within and between living environments, relationships between gut microbiota and human health continue to evolve our understanding of our own body’s internal habitat. We hear about probiotics and prebiotics, often in relation to supporting our metabolism, digestive, and immune function, but how much do we understand the amount of influence our diet has on our gastrointestinal microenvironment, health maintenance and disease prevention?

Do we all have the same type of gut bacteria?

The gut is populated with a unique set of intestinal bacteria collectively forming the gut microbiome. The human gastrointestinal tract contains over 100 million microorganisms that outnumber our own body cells and a hundred and thirty times more genetic material than our body’s own genome. We often think of the gut merely as a mechanical system, able to move and process food content and discard waste material but we are largely unaware of the fact that the large bowel alone harbors one of the richest microbial habitats on earth. Although genetics seem to be one of the determinants of one’s microbiome diversity, it is the balance within our gastrointestinal tract and how well we manage to sustain it through our life that contributes most to our health.

The quality of the gut is determined by: environmental exposures to toxins, antibiotics, pathogenic microorganisms, hygiene, exercise and sleep. Our eating habits influence our gut microbiome almost daily. For example, diets based on plant-based polysaccharides (starch and non-starch fibre) support Prevotella species in our digestive environment, while those rich in animal protein and saturated fat and sugar appear to favour an increase of Bacteroides. The diversity of bacteria and balance between the different populations in each part of the digestive tract enables bacteria to perform magnificent roles in our body. Some of these roles include: removing, manufacturing and absorption of nutrients; preventing the colonization of harmful bacteria; strengthening (innate and adaptive) immunity and gut function such production of metabolic by-products such as short chain fats (SCFA) that are essential for the maintenance of a healthy gut wall, brain resilience, and ability to achieve optimum weight.

The connection between the gut and the brain, mood and anxiety

Growing evidence suggests that how we deal with stress and our psychological states are influenced by our unique microbial ecosystem. Numerous mechanisms aid communication between the microorganisms in our intestines and our nerve cells through the production of neuroactive substances or through modulation of normal nerve signaling. For example, GABA (gamma-aminobutyric acid), which is the main amino acid-based inhibitory neurotransmitter, acting somewhat like a brake in the brain and spinal cord, that seems to be influenced by Bacteroides species. This class of bacteria appear to be inversely associated with depression. Likewise, there are significant relationships between types of gut bacteria and behavioural traits emerging from studies about stress, negative mood, sociability and psychological conditions, including autistic disorders. Lactobacillus and Bifidobacterium species, two of the most common classes of probiotic organisms found in health food supplements and targeted dietary interventions, appear to be helpful in both stress and depression.

Some fascinating work has shown that the use of specific bacteria can affect emotional processing by increasing resilience to negative stimuli and lowering levels of the stress hormone cortisol after just a few weeks. In irritable bowel syndrome (IBS), the addition of probiotic food supplementation may help to reduce feelings of anxiety, which highlights the intimate connection between the microbiome and the gut-brain axis. And In autism, studies have showed that altering microbiome diversity in the gut can lead to improvements in behavioural attitudes, communication and gastrointestinal health.

An analysis of the impact of gut microbiome diversity has revealed that people who consume a probiotic-rich diet, consisting of fermented foods like miso and tempeh, have lower levels of anxiety and stress. Conversely, higher levels of stress and anxiety have been connected to a poorer gut biodiversity, which also appears to be a cofactor in lower sleep quality. Not surprisingly then, findings regarding stool consistency attributed to dysbiosis (alterations/ imbalances in the gut flora) are consistent with animal studies showing that stress changes both the diversity and the numbers of bacteria in the gut.

How the gut microbiome affects immunity

Gut microbiome diversity has been shown to increase resistance against infection and improve immune function while reducing the risk of allergic conditions such as atopic dermatitis. It is the intestinal barrier which holds multiple lines of defence, with resident bacterial diversity being responsible for producing protective compounds, to ward off potentially pathogenic bacteria from colonizing the gut and causing inflammation and infection in other parts of the body. SCFA are a characteristic example of the relationship between our gut microbiome and the diet. The concentration of these small types of fat relies on the amount of fibre in our diet from foods such as vegetables, legumes, and whole grains. SCFA modify the activity of our immune system and protect the integrity of the intestinal barrier. Our guts have specialized receptor systems to assist communication between the resident bacteria and gut cells to elicit an immune response under infection also to support the development of immune (lymphoid) tissues, which are crucial for immune surveillance and regulating inflammation

Studies examining the effects of dietary modulation of the gut microbiome and immunity show that many Western diets can negatively influence one’s gut flora and immunity. A high intake of saturated fat, typically found in meats, dairy, butter, cakes, and biscuits promotes an increase in secondary bile acids (compounds originally secreted by our liver to aid the digestion of fat). Which stimulate the development of certain types of pathogenic bacteria alongside cell-dependent immune responses that predispose to colitis. With inflammatory bowel disease (IBD), what we see is that both environmental factors (diet, stress, antibiotics, and proton pump inhibitors) can lead to a disturbance in microbial richness in the gut alongside changes in the substances produced by gut bacteria. This is followed by immune dysregulation resulting in inflammation, injury of the gut barrier and the junctions that keep the gut cells tightly together, and disruption in the production of antimicrobial defense substances. Inflammatory bowel syndrome (IBS) is one of the conditions that can be improved by dietary modification geared towards specific carbohydrate-rich foods, probiotic supplementation, and strategies to help restore gut microbial diversity and the integrity and normal movement of the bowel.

There is a link between the ecology of the gut and weight management and there seemed to be a similar interplay between diet, microbiota and immune function/ chronic inflammation as shown in metabolic syndrome and diabetes. Some of the effects of poor biodiversity in the gut can alter several mechanisms such as hormonal as well as the immune system, leading to changes in blood sugar balancing (insulin resistance), appetite and fat deposition in the body. The potential benefits of gut microbiome diversity, through probiotic-friendly diets, strain-specific supplementation with friendly bacteria and tailoring of carbohydrate intake include: reduction of intestinal inflammation; immune rebalancing; lipid reduction or absorption; calorie saving; increase of fat breakdown; and suppression of fat storage; improved liver and gut barrier function; and modulation of appetite. Additionally, the consumption of viscous soluble fibre e.g. psyllium husk and inulin (found in foods such as Jerusalem artichokes, chicory and other vegetables and grains) and insoluble fibre (roughage), can improve our gut function and ecosystem by increasing satiety, promote microbe diversity and SCFA production, support gut barrier integrity and healthy cholesterol metabolism, and reduce inflammation.

IBS and SIBO (small intestinal bacterial overgrowth) often arising from similar causes or contributory factors including changes in microbiota populations and infections, most notably parasitic, as well as chronic fluctuations in normal gut motility and especially slower movement of the bowel as seen in constipation.

Rather than waiting for a chronic condition to launch in, its vital to maintain a healthy gut brain connection with biodiversity in the gut, by consuming enough plant fibre alongside a balanced intake of macronutrients and water. Colonic hydrotherapy – a great means of toxin removal – intermittent fasting, food variety to assist microbe variety and keeping away from calorie-laden processed foods, some often-neglected routines such as regular exercise and sleep hygiene. These are just a few of those ancient practices that can help us flow gracefully and steadily through the demands of modern living.

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