The fermentation of non-digestible substrates such food fibers and endogenous intestinal mucus is made possible by the vital capacities provided by the gut bacteria. Short chain fatty acid (SCFA) and gas production by specialized microorganisms is promoted by this fermentation. The main SCFAs generated are butyrate, propionate, and acetate.
Human colonocytes use butyrate as their primary energy source. It can also cause colon cancer cells to die and activate intestinal gluconeogenesis, both of which have positive effects on glucose and energy homeostasis. In order for epithelial cells to produce a state of hypoxia that maintains the balance of oxygen in the gut and guards against gut microbial dysbiosis, butyrate is required.
Through interacting with the gastrointestinal fatty acid receptors in the liver, propionate controls gluconeogenesis and satiety signaling. The most prevalent SCFA, acetate is used in cholesterol metabolism and lipogenesis in peripheral tissues and is also thought to be involved in central appetite regulation. Acetate is also a necessary metabolite for the growth of other bacteria. Increased synthesis of SCFAs has been linked to decreased insulin resistance and diet-induced obesity, according to randomized controlled trials.
Trimethylamine is produced by the gut microbiota from dietary phosphatidylcholine and carnitine (from meat and dairy), and as a result, the amount in the blood differs from person to person. Trimethylamine is converted to trimethylamine N-oxide in the liver, and this compound has been positively linked to an elevated risk of atherosclerosis and severe adverse cardiovascular events. With its powerful radical scavenging activity in vitro and high correlation with dietary fiber intake, indolepropionic acid appears to lower the incidence of type 2 diabetes.
Diversity of the microbiota and health
Those with inflammatory bowel disease,psoriatic arthritis, type 1 diabetes, atopic eczema, celiac disease, obesity,type 2 diabetes,and arterial stiffness, have consistently shown to have lower bacterial diversity than healthy controls. Smokers have significantly less variety in their gut microbiome when they have Crohn’s disease.A species-rich gut ecosystem is more resilient to environmental impacts, as functionally related microorganisms in an intact ecosystem can fill in for the function of other missing species, according to the link between disease and lower diversity.
Fecal microbiota transplantation has demonstrated the functional importance of the gut microbiome in humans. This method, which is now widely used for this purpose worldwide, is effective in situations of severe drug-resistant Clostridium difficile infection.Faecal transplants have been investigated but are currently not used in clinical practise for other illnesses.For instance, transplanting (allogeneic) feces from a lean healthy donor to recipients with metabolic syndrome led to improved insulin sensitivity and changed microbiota composition compared to utilizing autologous feces.
The impact of food and medication on the gut microbiota
The quantity of various bacteria in the stomach can be influenced by dietary habits and certain foods, which can therefore have an impact on health. Due to their high sweetness and low calorie content, high-intensity sweeteners are frequently employed as sugar substitutes. The gut microbiome of animals may be negatively impacted by these sugar substitutes, despite the fact that regulatory organizations have declared them to be “generally recognised as harmless.” Evidence suggests that the diversity and equilibrium of the gut microbiota are disturbed by sucrose, aspartame, and saccharin.
Animal gut microbiota have also been proven to be impacted by food additives, such as emulsifiers, which are widely used in processed foods. Animals fed relatively small amounts of the two common emulsifiers carboxymethylcellulose and polysorbate displayed less microbial diversity than mice not given emulsifiers. Inflammation-promoting Proteobacteria linked to mucus were enriched while Bacteroidales and Verrucomicrobia were reduced.
Dietary modification to influence the gut flora
The gut flora can change within days of altering food; striking variations were discovered after African Americans and rural Africans switched diets for just two weeks.The generation of butyrate increased 2.5 times in the African Americans who had a rural African diet due to an increase in the number of recognised butyrate-producing bacteria, which also led to a decrease in the synthesis of secondary bile acid.
These alterations were visible after just five days in a different study comparing drastic changes in diets based on plant and animal proteins. As recently demonstrated in the case of bread, healthy microbiota are resilient to temporal alterations caused by dietary interventions, indicating that homeostatic processes restore the original community composition.
Dietary fiber and prebiotic foods
The majority of national definitions of dietary fibre include edible carbohydrate polymers with three or more monomeric units that are resistant to the digestive enzymes found in the body. A portion of dietary fiber sources are fermentable, which indicates that they act as a growth medium for microorganisms in the distal colon.
Prebiotics are defined as food components or ingredients that are not digestible by humans but specifically or selectively nourish beneficial colonic microorganisms. Some non-digestible carbohydrates have been referred to as “prebiotics,” which are defined as food components or ingredients that are not digestible by humans.
Some scientists prefer the term “microbiota accessible carbohydrates,” which is essentially equivalent to fermentable dietary fibre in that it becomes available as a growth substrate for gut microbes that have the required enzymatic capacity to use them.
Foods high in probiotics
When given in sufficient proportions, probiotics are live microorganisms that help the host’s health. Foods, dietary supplements, and medications are just a few of the goods that can include probiotics.There are worries that most microbe supplements can’t grow in the stomach and don’t have an impact on the local population.Yet, probiotics can have a direct impact on the host, such as by modulating the immune system or producing bioactive substances, to have a positive impact on health that is independent of the gut flora. Many disorders have been examined to determine how probiotic supplementation affects treatment.
Newer microorganisms and combinations, probiotics and prebiotics (synbiotics), and individualized treatments based on profiles of the potential bacteria in inflammation, cancer, lipid metabolism, or obesity are some of the emerging fields of probiotic treatment. It has been demonstrated that the individualized properties of the gut microbiota are necessary for stable engraftment of a probiotic, such as Bifidobacterium longum, which supports the need for probiotic applications to be tailored to the individual.