In a review article published within the journal Biomedicines, scientists have provided an in depth overview of the inter-individual variation in gut microbiota and its association with food regimen and health.
Review: Links between Eating regimen, Intestinal Anaerobes, Microbial Metabolites and Health. Image Credit: POLIGOONE / Shutterstock
Human gut microbiota
The human gut microbiota refers to a various collection of microorganisms, including bacteria, fungi, archaea, and viruses. Anaerobic organisms that don’t require oxygen for growth and survival comprise the best microbial biomass in the massive intestine.
Although some organisms are dominant and widespread within the healthy human gut, a substantial variation in gut microbiota composition and variety is often observed between individuals. The gut microbiota produces a lot of primary and secondary metabolites that play a vital role in maintaining body homeostasis, akin to short-chain fatty acids (SCFAs).
Eating regimen is taken into account a big driver in modulating gut microbiota composition and activities, which in turn is related to each positive and negative health effects. An imbalance within the gut microbial community, also referred to as gut dysbiosis, is thought to associate with a variety of diseases, including metabolic diseases and colorectal cancer.
Relationship between food regimen, gut microbiota, and health
Dietary macro- and micronutrients play a big role in shaping the composition and functions of human gut microbiota. The effect of food regimen on gut microbiota starts from birth. In breastfed babies, gut microbiota predominantly consists of a bifidobacterial population, which is needed for the utilization of non-digestible human milk oligosaccharides. In contrast, formula-fed babies exhibit a more complex adult-like gut microbiota composition.
The introduction of solid food in infants results in the expansion of obligately anaerobic bacterial populations which are capable of metabolize more complex polysaccharides. Eating regimen changes the production of metabolites by the gut microbial community. People residing in rural areas generally exhibit higher levels of SCFAs, probably on account of higher consumption of dietary fibers.
The gut microbial community obtains energy from dietary compounds that escape digestion by host enzymes, akin to resistant starch, non-starch polysaccharides, oligosaccharides, and proteins.
Resistant starch is the first dietary polysaccharide degraded by the gut microbiota. Bacterial populations containing a fancy extracellular starch-degrading structure (amylosome) are capable of degrade resistant starch that can not be digested by host enzymes.
The second major dietary polysaccharides degraded by gut microbiota are non-starch polysaccharides, akin to cellulose, pectin, and insulin. Insulin and oligosaccharides are mainly utilized by anaerobic organisms to support growth. These compounds are also used as prebiotics to advertise the bifidobacterial community.
Regarding dietary fats, only 7% of the ingested amount reaches the massive intestine for gut microbiota usage. Dietary fats can influence gut microbiota composition in some ways, akin to by reducing microbial diversity and increasing bile acid secretion. Diets containing high levels of saturated fats are known to impair immune functioning, induce inflammation, disrupt intestinal barrier integrity, and trigger systemic diseases.
Dietary proteins are degraded by each host- and bacteria-derived proteases and peptidases to supply peptides and amino acids. Depending on intake, about 3 – 18 gm of dietary proteins reach the massive intestine every single day for microbiota usage. Peptides and amino acids produced from dietary proteins are either directly incorporated into microbial proteins or fermented to supply energy for the microbiota.
Fermentation of amino acids results in the production of ammonia, major SCFAs, and branched-chain fatty acids (BCFAs), that are commonly used as fecal markers of protein fermentation. Furthermore, bacterial deamination of fragrant amino acids results in the production of assorted phenolic compounds.
Increased consumption of a high-protein food regimen is thought to cause many health adversities, including inflammatory diseases and certain varieties of cancers. Excessive consumption of a high-fat and high-protein food regimen has been found to extend bacterial toxic metabolites, that are related to many health conditions, including migraine, hypersensitive syndrome, portal-systemic encephalopathy, and colorectal cancer.
Relationship between food regimen, gut microbiota, and immune system
The immune system plays a significant role in mediating the crosstalk between food regimen, gut microbiota, and health. Anaerobic microbial community present within the intestine ferment dietary carbohydrates and proteins to form SCFAs and lots of other breakdown products, which subsequently bind to G-protein-coupled receptors present on intestinal epithelial cells in addition to on regulatory T cells, resulting in inhibition of effector T cell response.
The gut microbiota ferments dietary fibers to supply SCFA butyrate, which plays a significant role in maintaining regulatory T cell functions. These immune cells increase the production of anti-inflammatory cytokines by T cells, which is required for immune activation against common antigens derived from dietary products and commensal bacteria.
The gut microbiota-derived SCFAs increase host immune responses to pathogens. Specifically, SCFAs prevent the colonization of pathogens by increasing the flexibility of intestinal macrophages to persistently eliminate pathogens.
Besides SCFAs, other metabolites derived from the gut microbiota can influence the host immune system in some ways, akin to expanding regulatory T cells within the small intestine and stopping intestinal inflammation.