During these series of articles I will explain why the digestive system and its functioning has become a major focus of my work with clients and just how important it is. I am going to tell you the signs you need to look out for that can indicate poor digestion and, more importantly, what you can do about it. From energy to immunologic support and much, much more, the gastrointestinal (GI) system (or digestive system as most know it) is essential to maintain optimal health of the whole body. It does this by providing the body with a continual and balanced supply of water, electrolytes, and nutrients, amongst other things too. Join me for this series on how exactly it is required to keep the internal harmony (homeostasis) and make you feel at your very best!
The gastrointestinal (GI) tract extends from the mouth to the anus and is organised into well-defined ‘layers’, which are absolutely fascinating! We now understand much more about these ‘layers’ and how they contribute to vital activities in each region of the body. The main overall function of the GI tract, as you can probably guess, is to ingest, digest and absorb the nutrients, and lastly eliminate the waste. Even from this basic understanding we can see how slight dysfunction could impact how we feel and eventually lead to disease.
To support our energy and health the GI system must succeed at:
1) Moving food through this intricate network of tubes and hollows.
2) Secreting potent digestive juices, enzymes and then be able to digest the food.
3) Absorb water, various electrolytes, and digestive products that are the building blocks of life.
4) Circulate blood through the gastrointestinal organs to carry away the absorbed substances to where they are needed.
5) Achieving control of all these functions by local nervous and hormonal systems[i] that are so complex they make the mind boggle!
Straight away what becomes apparent is this must involve a stable interaction with other organ systems so we can live and hopefully thrive. There are many examples of this that I could use. For instance, the gall bladder delivers bile and enzymes into the gut through its ducts to aid the digestion of fats (like detergent to wash out the dishes). A rich blood supply is needed to the GI tract – we know stress is related to IBS. This is not surprising as stress turns off digestive activity (it down-regulates something called the parasympathetic nervous system or rest and relaxation system) and increases sympathetic nervous tone (stress response). And lastly, something called the lymphatic system assists in cleaning out the guts to improve the immune activities and prevent diseases.
The GI systems also hosts a wide variety of microbes (“the microbiome”), which as soldiers, protect the GI tract from an invasion by foreign microbes, and exerts vital functions to help in keeping the homeostasis between the different organ systems[ii]. All of this is quite simply, very mesmerising and we have barely even covered the basics…you can understand why some dedicate their whole lives just to understanding this system alone!
But how does the GI tract know what to do? Well, it talks to the brain and the brain talks back to it – something called the brain-gut axis (just like a telephone line between the two). The brain-gut axis modulates gastrointestinal function via the regulation of theses digestive ‘layers’; it literally communicates through these different ‘layers’ to understand what is going on in the body and what needs to be produced to survive. They exchange information to help each other out so you can survive.
This axis seems to be regulated by a feedback system where the brain acts on gastrointestinal and immune functions that help to shape the gut’s microbial compositions (what bugs live there down below), and in turn, the gut microbes make neuroactive compounds, including neurotransmitters (messengers such as serotonin, our happy hormone) and metabolites that act on the brain to regulate its signals.
These interactions could occur in various ways: our microbes communicate via something called the vague nerve, which could be thought of a major highway that connects the brain and the digestive tract, and microbial made metabolites interact with the immune system, which maintains its own communication with the brain2. Therefore, the gut and brain you can immediately see can play a variety of roles. Not surprisingly, appetite regulation, weight control, modulation of the immune system, and the coordination of the gastrointestinal tract with the overall physical and emotional state of your body!
However, several interactions and functions work not only via the vagus nerve, but also through the endocrine, or hormonal, (hypothalamic-pituitary-adrenal-axis) system, immunological and metabolic pathways[iii].
Beneficial bacterial have been found to decrease inflammation and improve immune functions[iv], since eosinophils (the white blood cells of the immune system) associated with allergic reactions and to fight multicellular parasites, as well as certain infections, are commonly detected in normal mucosal sample tissues taken from all sites within the GI tract[v]. Naturally probiotics have gathered lots of interest and I am sure many reading this may even take probiotic supplements, but are they helpful?
The absorption of probiotics supplements have shown to exert a meaningful reduction on the incidence of respiratory tract infections, although the exact mechanisms behind it are still not clear. Scientists have proposed that it might be via a few different routes – by directly competing with an infectious organism, a connection among the tissue of the gut and the respiratory tract, an enhancement of the immune system, and that the health of the bowel or its resident population might directly affect the health of the lungs[vi],[vii],[viii].
Did you know a healthy microbiota digest short-chain fatty acids that tend to increase LDL cholesterol (“the bad cholesterol”), therefore reduces the amount of it in the blood, thus decreasing the risk of cardiovascular diseases[ix]?
Did you know the GI system contains 95% serotonin (“the antidepressant neurotransmitter”) excreted; this neurotransmitter plays a number of rules like mood influencer, motility and relaxation of the GI tract thus preventing constipation, and decreasing the transit time[x] (the amount of time it takes for food to pass from eating to being excreted). It is worth to mention that each part or ‘layer’ of the GI tract is adapted to its specific functions: some to simple passage of food (the oesophagus); others to temporary storage of the food (stomach); and others to digestion and absorption (small intestine)1.
Disorders of the mucous membrane (a protective layer that surrounds the digestive tract) and the microbiome results in malabsorption of nutrients and vitamins especially the fat-soluble vitamins (A, D, E, K) essential for the spermatogenesis (sperm formation), which can negatively affect the reproductive system. Also the urinary tract benefits from the competitive inhibition of the beneficial bacteria of the gut by inhibiting the growth of pathogenic bacteria, thus decreasing the incidence of the urinary tract infections!
Skeletal, muscular, and the integumentary system (our skin, hair and nails) are also benefited from an optimal absorption and beneficial bacteria in the GI system. Calcium and magnesium are essential to decrease the risk of osteoporosis.
We need to keep optimal levels of amino acids (proteins) in the body to avoid the subtraction of these from the muscle for maintaining more important issues when necessary And finally, the utilization of prebiotics and vitamins which prevent skin diseases like eczema and keep the skin in optimal conditions .
In summary, the GI system and its microbiome have many ‘layers’, functions and communication methods that are proven to have a great influence in keeping other organ system’s healthy and harmonic, and without optimal functioning we can not expect optimal health and wellbeing. Watch out for part II in this series where I will be going into more specific depth on these ‘layers’ and how you can recognise in your own body and mind where digestive improvements need to be made to resolve health challenges.
[i] Guyton AC. Textbook of medical physiology. 11th ed. Philadelphia: Elsevier Inc.; 2006. Chapter 62, General Principles of Gastrointestinal Function; p.771.
[ii] Schmidt C. Mental health: thinking from the gut. Nature. 2015 Feb 26;518(7540):S12-5.
[iii] Budzyński J, Kłopocka M. Brain-gut axis in the pathogenesis of Helicobacter pylori infection. World J Gastroenterol. 2014 May 14;20(18):5212-25.
[iv] Ordovas JM, Mooser V. Metagenomics: the role of the microbiome in cardiovascular diseases. Curr Opin Lipidol. 2006 Apr;17(2):157-61.
[v] Yantiss RK. Eosinophils in the GI tract: how many is too many and what do they mean? Mod Pathol. 2015 Jan;28 Suppl 1:S7-21.
[vi] McVay MR, Boneti C, Habib CM, Keller JE, Kokoska ER, Jackson RJ, Smith SD. Formula fortified with live probiotic culture reduces pulmonary and gastrointestinal bacterial colonization and translocation in a newborn animal model. J Pediatr Surg. 2008 Jan;43(1):25-9; discussion 29.
[vii] Glück U, Gebbers JO. Ingested probiotics reduce nasal colonization with pathogenic bacteria (Staphylococcus aureus, Streptococcus pneumoniae, and beta-hemolytic streptococci). Am J Clin Nutr. 2003 Feb;77(2):517-20.
[viii] Hatakka K, Saxelin M. Probiotics in intestinal and non-intestinal infectious diseases--clinical evidence. Curr Pharm Des. 2008;14(14):1351-67.
[ix] Wong JM, de Souza R, Kendall CW, Emam A, Jenkins DJ. Colonic health: fermentation and short chain fatty acids. J Clin Gastroenterol. 2006 Mar;40(3):235-43.
[x] McLean PG, Borman RA, Lee K. 5-HT in the enteric nervous system: gut function and neuropharmacology. Trends Neurosci. 2007 Jan;30(1):9-13.
