A microbiome is the collective genetic makeup of microbes in a given habitat. Human gut microbiomes are microorganisms living in the gut. It is also known as "gut microbiota" or "gut flora". Our bodies are ecosystems. We have microbes all over us, like on our skin, in our nose, and in our ears, but most of them reside in our gastrointestinal tract, in our colon. In the colon, colon cells secrete mucus to keep these microbes in their right spots. These microbiomes are not harmful as long as they are in their correct place. In fact, they are helpful.
We know our gut microbes help us with the digestion of complex, fiber-rich foods, but they are actually more helpful than that. Our gut microbiome can influence our biology. They influence our metabolism, immune system, and also our Central Nervous system.
Gut bacteria serve the host by strengthening the host's immune system. In addition to regulating gut motility, creating vitamins, converting bile acid and steroids, metabolising xenobiotics, absorbing minerals, and activating and eliminating toxins, genotoxins, and mutagens. Gut bacteria are beneficial to the host in a number of ways.
Short-chain organic acids are abundantly produced in the proximal colon. These short-chain fatty acids (SCFA) serve as energy sources for the intestinal mucosa and peripheral body tissues. By influencing colonic water absorption and lowering faecal pH, these SCFA in turn has an impact on bacterial development in the colon. Additionally, Oxalobacter formigenes control the oxalic acid balance and stop kidney stones from forming. Isoflavones are also metabolised by gut bacteria. Breast and prostate cancer, heart disease, osteoporosis, and menopausal symptoms can all be prevented by isoflavones.
What is the relation between gut microbiome and disease?
Microbes cause the fermentation of nutrients into absorbable forms like carbohydrates into short-chain fatty acids. These SCFAs have anti-inflammatory and immunomodulatory effects. Components of the bacteria themselves are also released and result in secondary beneficial effects for the host. These effects include preservation of gut epithelium, synthesis of vitamins, and immune system signalling molecules, activating and inhibiting specific responses.
When there is bad gut health, these functions are impaired, leading to inflammation and a compromised immune system. This can cause conditions like metabolic syndrome, inflammatory bowel disease, cancer, multiple sclerosis, Crohn's disease, asthma, and obesity.
Hence, increasing your gut microbe diversity is important for better metabolic markers, immune markers, and less inflammation.
Reduced variety and alterations in the makeup of the gut bacteria may be linked to obesity. A key factor in determining susceptibility to obesity and related metabolic problems is gut flora. It has been discovered that the ratio of firmicutes to bacterioides is connected with body weight, with the ratio being higher in obese individuals.
Diabetes is influenced by alterations in gut flora. Early intestine microbial colonisation at birth influences the development of diabetes and is influenced by a baby's eating habits, birth weight, and delivery procedure. Since islet destruction may be a result of cross-talk between gut bacteria and the innate immune system, abnormal gut bacteria may contribute to the pathogenesis of Type 1 Diabetes.
Cardiovascular disease risk is directly correlated with gut bacteria. The high permeability of the intestinal wall may result in the transfer of bacteria and/or endotoxins, which may be a significant trigger for the activation of inflammatory cytokines in chronic heart failure.
Cancers like gastrointestinal cancer and prostate cancer are influenced by the presence of microbial pathogens or a disturbance in the native gut bacterial flora. Commensal bacteria have been acknowledged as significant cofactors in the development of colon cancer. Butyrate, a significant nutrient for healthy colon cells, has been demonstrated to inhibit cell growth and trigger apoptosis in human colon cancer cells, whether used alone or in conjunction with propionate.
Numerous other illnesses and symptoms, including poor sleep, rheumatic disorders, and kidney problems, are also linked to gut microbes. Numerous diseases may be brought on by dysbiosis of the gut bacterial ecosystem in humans. For instance, the use of antibiotics and surgery might result in pseudomembranous colitis, sepsis from Escherichia coli, Enterococcus faecalis, and Enterococcus faecium, as well as intra-abdominal abscesses from Bacteroides fragilis. Intestinal symptoms such as bloating, stomach pain, and diarrhoea have been linked to an imbalance in the makeup of the gut flora. IBS-Allergies and IBD may be brought on by the host and indigenous gut bacteria interacting reciprocally. In a genetically vulnerable host, IBD may result from an aberrant immune reaction against the commensal microbiota. An inflammatory condition called ulcerative colitis (UC) is one of the two major idiopathic IBDs that mostly affects the colon and rectum. Environmental variables, host immune system issues, gut microbiota dysbiosis, and genetic factors are thought to have a role in the pathogenesis of UC. Another class of IBD is Crohn's disease (CD). It is believed to be an autoimmune condition where the body's immune system attacks the digestive tract and results in inflammation.
Can diet influence your gut?
Fiber is the fuel of the gut microbiome. Changing your diet alone can help you change your gut flora from low to high microbiota diversity. It is in your hands to direct your inner microbes to a more healthy state through the food you eat.
So, to increase your gut health and to increase your diversity of microbes, it is important to increase the intake of fiber in your diet, which is the fuel of the gut microbiome. A diet high in fiber helps to keep the mucous layer thick, which in turn helps to keep the microbes away from the host tissue. An increase of 10g of fiber per day decreases your chances of dying.
Fiber is the fuel of the gut microbiome. Changing your diet alone can help you change your gut flora from low to high microbiota diversity.
Prebiotics are similar to fiber; they are purified dietary fiber. A mixture of dietary fiber is much better than a single prebiotic. The best way to include prebiotics in your diet is to include a diverse plant diet and fermented foods.
Dietary components like polyphenols, fiber, and carbs can alter the composition of the gut flora. The two primary types of polyphenols we consume through food are phenolic acids and flavonoids. The growth of some pathogenic bacteria, including Clostridium perfringens, Clostridium difficile, and Bacteroides spp., was shown to be inhibited by tea phenolics and their derivatives, whereas commensal anaerobes, including Clostridium spp., Bifidobacterium spp., and Lactobacillus spp., were only mildly harmed. When we eat simple foods, they get digested in the stomach and released into the bloodstream, which increases our blood sugar levels. It doesn't reach your gut microbiome, which causes your gut microbiome to starve. This starvation leads them to eat you, your mucous lining of the GI tract, which is made up of carbohydrates and is the backup food source of these microbes. Because of this, microbes start moving closer to the epithelium and the inflammation markers start.
Artificial sweeteners have a negative impact on your microbiota, leading to changes in metabolism. It has the potential to turn healthy bacteria into harmful microbes, causing serious health conditions. Hence avoid their use in your daily routine.
Summary:
Numerous disorders, including IBD, obesity, diabetes, cancer, HIV, and autism, has been linked to gut flora. These disorders could manifest when the gut flora is out of balance. The primary role of gut bacteria in the development of these disorders is immunoregulatory action. Disease susceptibility, including IBD, diabetes, and obesity, is impacted by diet-induced dysbiosis. Prebiotics and probiotics have been extensively utilised in the treatment of several disorders in recent years and have demonstrated significant benefits.
References:
Zhang, Y. J., Li, S., Gan, R. Y., Zhou, T., Xu, D. P., & Li, H. B. (2015). Impacts of gut bacteria on human health and diseases. International journal of molecular sciences, 16(4), 7493–7519. https://doi.org/10.3390/ijms16047493
Fan, Y., Pedersen, O. Gut microbiota in human metabolic health and disease. Nat Rev Microbiol 19, 55–71 (2021). https://doi.org/10.1038/s41579-020-0433-9