The gut microbiota and good health

I am starting off this year with pieces on the gut micro­biota-an area engaging a lot of interest internationally.

The terms microbiota and microbiome are often used interchangeably, although they have different meanings. Microbiota first refers to the prokaryotic organisms (bacteria and archaea) and eukary­otes (e.g., protozoa, fungi, algae, and multicellular parasites) that coexist in symbiosis with us. Microbiome means a complex ecosystem of microbial species that colonize our body, their genome, and the surrounding envi­ronment in which they live (Scuderi et al.Gut Microbiome in Retina Health: The Crucial Role of the Gut-Retina Axis. Frontiers in Microbiology. www. frontiers.org. January 2022 | Volume 12 | Article 726792)

The microbiome comprises a microbial community that exceeds 100 trillion microorganisms, distrib­uted with a density of 1011–1012 per milliliter. To get an idea of the biological role of this population, just think that, while the human genome consists of approximately 23,000 genes, the gut microbiome encodes more than 3 million genes and pro­duces thousands of metabolites. The gut microbiota performs immune and metabolic functions of fundamental importance to the body. The mainte­nance of the gut microbiota qualita­tive and quantitative composition is essential for the maintenance of our health.

The mammalian intestine hosts a microbial community of approxi­mately 1,000–1,500 bacterial species called the “microbiota,” destined to evolve over the course of the host’s life and over the generations and sub­ject to environmental changes. It has been amply demonstrated that the composition of the intestinal micro­biota is also influenced by diet, age, lifestyle, and the presence of inflam­matory processes. The composition of the microbiota differs substantially from individual to individual. The commensal microorganisms that reside in the intestine exceed human somatic cells at a ratio of about 10:1. In healthy adults, the microbiota is primarily composed of five bacterial phyla: Firmicutes (79.4%), Bacteroi­detes (16.9%), Actinobacteria (2.5%), Proteobacteria (1%), and Verrucomi­crobia (0.1%).

Normally, the gut microbiota consists of a high diversity and abundance of microbial popula­tions, and this condition is known as “eubiosis” (balance). Over the span of a lifetime, a wide range of factors, including an incorrect diet, pathological conditions, drug abuse, pharmacological therapy, and many others, can alter diversi­ty and abundance of the microbio­ta leading to a state of “dysbiosis” (imbalance).

The symbiotic relationship between the gut microbiota and the host organism has been de­scribed as mutually beneficial: the host provides the nutrients and a suitable habitat for the microbiota, while the gut microbiota supports the host’s intestinal development and maturation by providing nutrients. The microbiota is able to control and influence certain segments of the physiology of the host such as the immune system, the digestive system, and the brain. The microbiota plays a vital role in the formation of the host’s immune system, and it can be said that there is real cross-talk between the host immune system and the gut microbiota which allows the development of the host’s tolerance to the harmless antigens of the microbiota.

The human gastro-intestinal (GI) tract is one of the largest in­terfaces (250–400 m2) between the host, antigens, and environmental factors in the human body. The human gut microbiome varies (in both composition and function) in each of the anatomical regions of the GI tract as these have different characteristics in terms of physiology, pH, oxygen tension, digestive flow rate, availability of substrates, and host secretion. Therefore right from the From the duodenum to the rectum, an increasing quantitative microbial gradient and a decreasing qualita­tive microbial gradient occur, and shows a progressive reduction of aerobic bacteria (survive and grow in oxygenated environment) in fa­vour of obligate anaerobes (grow and survive only in the absence of oxygen).

The human intestinal tract harbours a diverse and complex microbial community which plays a central role in human health. It has been estimated that our gut contains in the range of 1000 bac­terial species and 100-fold more genes than are found in the human genome. This community is com­monly referred to as our hidden metabolic ‘organ’ due to their immense impact on human well­being, including host metabolism, physiology, nutrition and immune function. The gut microbiome coevolves with us and that chang­es to this population has major consequences, both beneficial and harmful, for human health.

The disruption of the gut microbiota (or dysbiosis) can be significant with respect to pathological intestinal conditions such as obesity and malnutri­tion, systematic diseases such as diabetes and chronic inflammatory diseases such as inflammatory bowel disease (IBD), encom­passing ulcerative colitis (UC) and Crohn’s disease (CD). The intestinal microbiota of healthy individuals is known to confer a number of health benefits relating to, pathogen protection, nutrition, host metabolism and immune modulation.

Dietary polyphenols are com­pounds of natural origin present in food items such as vegetables, fruits, cereals, tea, coee, dark choc­olate, cocoa powder, and wine. Polyphenols act in the gut micro­biota to favour the increase of beneficial bacteria and hamper the increase of pathogenic bacteria. The microbiota act on polyphe­nols to increase their bioavail­ability. The two way interactions between polyphenols and the gut microbiota affect human metab­olism and reduce cardiometabolic risk. A significant portion of unabsorbed polyphenols is acted upon by the colonic bacterial enzymes in the large intestine, and consecutively generate metabo­lites having diverse physiological implications. Colonic microflora may transform the polyphenols into bioactive compounds, which have the ability to influence the intestinal ecology and aect human health. Cocoa is an excellent source of polyphenols (Sigh et al. Beneficial Effects of Dietary Poly­phenols on Gut Microbiota and Strategies to Improve Delivery Efficiency. Nutrients 2019, 11, 2216; doi:10.3390/nu11092216).


[The writer is the Chief Pharmacist

Cocoa Clinic]

By Dr. Edward O. Amporful

Show More
Back to top button