The gut or gastrointestinal tract is a long tube that starts at the mouth and ends at the anus. It is within this system that what we eat is processed with nutrients being absorbed and waste being excreted as stool(1). The process of digestion can be broken into four main sections, oral processing to mechanically break down food; gastric processing to begin the chemical breakdown; small intestinal processing to allow the absorption of nutrients from macromolecules; then water removal occurs in the colon(1,2).
This digestive process is known to be aided through the action of the gastrointestinal microbiome. The gastrointestinal microbiome is a diverse collection of microorganisms (including bacteria, fungi and viruses), which populates the gut of all mammals(3). Bacteria are the most studied constituent of the microbiome, up to 100 trillion of them are known to exist within the human gut, the majority being located in the cecum of the small intestine with the Bifidobacterium and Lactobacillus families being predominant(4). Exposure to microorganisms within the birth canal means your microbiome begins formation from the moment you are born(5). Furthermore, recent research suggests that the developing baby also comes in contact with these microbes within the womb(6). As a result, the maternal microbiome can impact factors such as obesity risk(7,8) , mental health(9) and immune response(10) within their child.
Gut dysbiosis is the term for an imbalance between beneficial and harmful strains of bacteria. The result of this occurring can trigger gut hyperpermeability, with decreased selectivity of the gut barrier, allowing passage of unwanted particles(13). This hyperpermeability is often the basis of intolerances or allergies due to small food particles or toxins to passing through the gut barrier and being identified in the blood by the immune system as foreign. Furthermore, gut dysbiosis has also been associated with gas, bloating, diarrhoea and constipation as well as issues such as trouble sleeping, unintentional weight loss or weight gain and more (14,15). Alongside inheriting gut flora from our mothers, our microbiome can be modulated through diet. Studies have found that high sugar and processed high fat foods promote harmful bacterial growth(11). On the other hand, foods high in fibre encourage growth of protective bacteria(12).
Future advances in our understanding of the importance of the microbiome and the mechanisms by which probiotics can effectively modulate it, may not only help to improve the credibility of probiotic supplementation but also prompt development of novel strategies for treatment or prevention of diseases.
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- Integrative HMP (iHMP) Research Network Consortium .The Integrative Human Microbiome Project: dynamic analysis of microbiome-host omics profiles during periods of human health and disease. Cell Host Microbe. 2014 Sep 10;16(3):276-89.
- Bäckhed F, Roswall J, Peng Y. Dynamics and Stabilization of the Human Gut Microbiome during the First Year of Life. Cell Host Microbe. 2015 May 13;17(5):690-703.
- Aagaard K, Ma J, Antony KM. The placenta harbors a unique microbiome.Sci Transl Med. 2014 May 21;6(237):237
- Li Y. Epigenetic Mechanisms Link Maternal Diets and Gut Microbiome to Obesity in the Offspring.Front Genet. 2018 Aug 27;9:342.
- Hou YP, He QQ, Ouyang HM. Biomed Res Int. 2017;2017:7585989. Human Gut Microbiota Associated with Obesity in Chinese Children and Adolescents.
- Dinan TG, Cryan JF. The Microbiome-Gut-Brain Axis in Health and Disease.Gastroenterol Clin North Am. 2017 Mar;46(1):77-89.
- Timothy W. Hand. Linking the microbiota, chronic disease and the immune system.Trends Endocrinol Metab. 2016 Dec; 27(12): 831–843.
- T. Sen. Diet-driven microbiota dysbiosis is associated with vagal remodelling and obesity. Physiol Behav. 2017 May 1; 173: 305–317.
- Jill A. Parnell Prebiotic fibre modulation of the gut microbiota improves risk factors for obesity and the metabolic syndrome.
- Arianna K. DeGruttola,Daren Low,A.Mizoguchi.Current understanding of dysbiosis in disease in human and animal models Inflamm Bowel Dis. 2016 May; 22(5): 1137–1150.
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- Plaza-Díaz J.Adamdec1, Ednrb and Ptgs1/Cox1, inflammation genes upregulated in the intestinal mucosa of obese rats, are downregulated by three probiotic strains.Sci Rep. 2017 May 16; 7(1):1939
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