It is said that Hippocrates once said “All disease begins in the gut”.

The gastrointestinal system is an excellent example of the dynamic, complex physiology and systems interconnected and interdependency in the human body. Although not integral parts of the digestive system, the nervous, hormonal/endocrine and immune systems have
considerable input into, and receive output from, the digestive system. Disruption of these different physiological systems can lead to disease. When in balance it is supportive of and contribute to health of the whole organism/human. To understand the influence, we need to consider the following realities:

Gastrointestinal Tract

Interesting facts about the GIT;

  • It has 10 times more cells than the whole of the rest of the body combined
  • It contains 2/3 of the immune tissue in the body
  • It produces 3/4 of the neurotransmitters in the body
  • It has greater metabolic activity than the liver
  • About 70% of the lymph tissue is associated with the gut, named the gut-associated lymphoid tissue or GALT
  • The Gastrointestinal mucous membrane surface is the largest interface between the internal body and the external world. It covers more than 400 square meters which is > 200–fold the surface of the skin area.
The various functions of the GI tract can be summarized as follows;

  • Digestion and absorption of nutrients
  • Detoxification and Elimination of waste
  • Intestinal Barrier function
  • Immune surveillance function to distinguish good from bad
  • Enteric nervous system

Other systems involved with the GI tract;

  • Vagal nerve and autonomic nervous system response
  • Endocrine/hormonal function
  • Neurohormonal production
  • Lymphatic system
The Gastrointestinal tract is influenced by external and internal environmental influences;

  • Infections
  • Toxins
  • Artificial sweteners, colourants and preservatives
  • Medications
  • Food Intolerances
  • Disruption of the probiotic community (microbiome) in the intestinal tract
  • Physical and emotional trauma
  • Stress

There is a direct Gut-Brain connection through the following pathways;

It is becoming increasingly evident that bidirectional signalling pathways exists between the gastrointestinal tract and the brain; through nerves, hormones, inflammatory molecules and the gut microbiota. This relationship is commonly dubbed the gut–brain axis. The complete system integrates information from within as well as from the environment outside the body to generate optimal digestion and brain function.

  • The gut-brain axis is involved in regulatory loops within the body (the hormonal and immune system). It is also closely linked to the environment around us. The brain responds to psychosocial influences, emotional highs/support and lows/trauma and stressful situations. The gut and intestinal microbiome respond to nutrition or lack thereof, infections, toxins, artificial sweeteners, preservatives, artificial colourants, medications and intolerant foods.
  • The Vagal Nerve is the longest nerve running from the brain to the organs in the chest and abdominal cavity. The vagal nerve sets off the parasympathetic or sympathetic response. These two components of the autonomic nervous system are in ebb and flow and the body can either experience a Sympathetic (flight of fight) or a Parasympathetic (rest, digest or repair) response. The vagal nerve is important in the gut-brain axis and its role in the stress response
  • Sensory information generated in the gut reaches the brain (gut sensation), and the brain sends signals back to the gut to adjust function (gut reaction).
  • The role of Serotonin in the intestinal and brain is crucial. It is excreted by serotonin containing endocrine cells in the first part of the intestinal tract. It helps the digestive process proceed in a normal fashion. Serotonin activates sensory nerve endings in the vagal nerve and enteric nervous system. A more concentrated serotonin excretion in conditions such as food poisoning support the intestinal tract to expel the toxins and food in both directions (vomiting and diarrhoea). Lowered serotonin excretion in the gut leads to lowering in brain serotonin and result in depression.
  • All the other Neurohormones also activates sensory nerve cells in the vagal nerve and enteric nervous system and are used by the brain to support brain function. These are also excreted by endocrine cells in the intestinal mucous membrane. Disruption of brain function can therefor result if secretion of the neurohormones are reduces. This can happen because of lack of certain nutrients, inflammation of the intestinal lining and disruption of the other systems that are involved. The result on a brain level can be depression, ADD, ADHD and many more.
  • The Immune system response, against intruders, results in inflammatory molecules that reach the brain via the lymph and the blood. Inflammation on the intestinal barrier can result in inflammation on the brain barrier. Breakdown of the tight junctions (increased intestinal permeability or “leaky gut”) occurs in the intestinal mucosa as a result from an unbalanced chronic inflammation response. This then allows for increased two-way communication, with larger molecules of undigested protein, intestinal flora, pathogenic bacteria, fungi, parasites and toxins gaining entrance into the portal and lymphatic systems; loading the liver, blood and brain with extra ‘information’. Now we have a perfect storm for creating a systemic or brain disease process.
  • The mucosal barrier micro-environment (probiotic flora) heavily influences the immune response that results from antigen interaction. It therefore plays an important role in the gut-barrier function. It also has a role to play in digestion and the function and health of all the organs and organs systems. Thus, it makes sense that disruption (changes in the microbiome population) has a far-reaching effect on general health (body and brain).
  • Hormonal (endocrine) balance influences the digestive system. Estrogens, progesterone, testosterone, DHEA, cortisol, melatonin and thyroid hormones play a part in the digestion, absorption and elimination function of the gastrointestinal system. Steroid hormone glucuronidation (detoxification)happens in the gut, as well as a number of other organs. Hormones are important messages both within the brain and between the brain and the body. The brain contains receptors for thyroid hormones (hormones produced by the thyroid) and the six classes of steroid hormones, which are synthesized from cholesterol (androgens, estrogens, progestins, glucocorticoids, mineralocorticoids and vitamin D). A major part of estrogen is metabolized in the brain and estrogen can affects mood.

 The close interaction of all the above pathways plays a crucial role in the generation of optimal gut function, brain function, emotions, hormonal balance and general wellbeing. It should therefore be clear that disruption of the gastrointestinal lining leads to a state of unwellness and the development of a disease process. Inflammation is the underlying disruption in all disease processes.