Digestion in the Modern World - part 2

Gut disorders and constipation - a three part series by Olivier Sanchez

A quick insight into the digestive system

Digestion involves the mechanical and chemical breakdown of food into smaller components that can be more easily absorbed and assimilated by the body. A host of digestive organs work in harmony (including the digestive tract, pancreas, liver, and gallbladder) to ensure that we are able to extract the nutrients from food to power the demands of the body. Once food has been efficiently digested, it needs to be absorbed into systemic circulation.

The upper part of the digestive tract, consisting of the mouth, oesophagus, stomach and the initial part of the intestines (the upper duodenum), is where most chemical digestion takes place. Digestion begins in the mouth, with the mechanical action of chewing, enzymes contained inside saliva (amylase enzymes initiate the breakdown of starches). The stomach, via the release of acid release, continues the digestive process by allowing the breakdown of proteins and fats (due to the effect of pepsin and gastric lipase respectively), and mineral dissociation (stomach acid is required to assimilate minerals). The release of the intrinsic factor by stomach cells is essential to chaperone B12 and allow for its absorption by the colon. Highly corrosive stomach acid also sterilises the milieu, the first barrier against pathogenic microbes ingested with food.

The pancreas secretes alkalising compounds to increase the pH of chyme (a mixture of partially-digested food and stomach juices), as well as digestive enzymes that allows for the continuous breakdown of food. The brush border, the upper part of the intestinal tract, also secretes digestive enzymes.

At the same time, the liver produces bile, which is collected and distributed in great amount by the gallbladder, allowing for the emulsion of fats (breakdown of fat into fatty acids) and the absorption of fat soluble compounds (e.g., fat soluble vitamins). Bile also displays mild laxative capabilities.

Nutrients are now ready to be absorbed. Most nutrient absorption occurs in the jejunum, the central area of the small intestine. The formation of cellular villi and microvilli increases the surface of absorption and the motility of food through the small intestinal tract.

​By the time food remains enter the colon, it is ready for elimination. However, the colon is also the part of the digestive tract where useful material is reabsorbed. This includes water (the large intestine plays a crucial role in maintaining positive water balance), electrolytes and certain vitamins. While the colon doesn’t produce digestive enzymes, the digestive process is continued, being taken over by the resident microflora. Gut bacteria release short-chain fatty acids and a multitude of other health-supporting metabolites feeding on dietary fibre and other nutrients (e.g., sugar and undigested food components). 

​Compromised digestion
The timely movement of food and fluid through the digestive tract is essential to digestion, absorption and elimination. Disrupted peristalsis and the consequent slowing down or speeding up of this process has been associated with many conditions including gastroesophageal reflux disease (GERD) , SIBO/SIFO, constipation and/or diarrhoea, and complications related to malabsorption and impaired detoxification.

These processes can be disrupted by many factors, including stress (anxiety, depression, overwhelming life demands and poor coping mechanisms), eating too fast, eating too much and mixing too many food groups in one sitting, drinking too much liquid with a meal, eating on the go or eating while working. Again, relying on poorly-nutritious ultra-processed food products may irritate the lining of the digestive tract, fuel inflammatory responses and disrupt enzymatic and absorptive capabilities. A lack of dietary intake will also play is part in poor motility and waste retention.

Low stomach acid can have a knock-down effect on all processes occurring at any stage of digestion. As explained earlier, stomach juices are essential to break down proteins and fats and the assimilation of minerals and vitamin B12. Low stomach acids due to suppressed digestive capabilities under the action of stress (or chronic inflammation, or certain drugs) can lead to proteins putrefying inside the digestive tract and produce gas, leading to bloating and abdominal discomfort and, in severe cases, debilitating pain. The absorption of nutrients and amino acids (the building blocks of life) can be greatly compromised as a result, even more so if sugar is present. Sugar fuels inflammatory processes and also plays a key role in dysbiosis, immune dysregulation and increased intestinal permeability.

Constipation
Constipation is one of the most common medical complaints in the western parts of the world. A significant portion of the population describe being constipated continuously or frequently.

nternationally, the incidence of constipation varies, depending largely on dietary habits. Constipation can occur at any age, and is more common among individuals who resist the urge to move their bowels at their body’s signal especially in the morning. Also, this often happens when children start school or enter daycare and feel shy about asking permission to use the bathroom or are prevented to do so. It also can happen to adults who are in jobs where they cannot take bathroom breaks at will. Constipation is more common in women than in men and is especially likely to occur during pregnancy. Dietary changes linked to ageing may also be involved. People over age 65 and particularly women are more likely to experience constipation.

Constipation is an acute or chronic condition in which bowel movements occur less often than usual or consist of hard, dry stools that are painful or difficult to pass. It is characterised by infrequent bowel movements (less than 3 times per week), stools that are difficult to pass or have a hard consistency, and a sense of incomplete evacuation, as well as abdominal bloating.

When waste sits or moves very slowly throughout our digestive tract, it gets fermented by microbes and becomes a literal breeding ground for all kinds of opportunistic and often pathogenic microbial species. These species than produce all kinds of toxins that create a stress response in our body and increase whole body inflammation levels. Therefore, constipation is a very serious condition, especially if chronic.

Clinical observations display a very concerning picture with many people only going to the toilet once a week or even less often. This problem can significantly impact the quality of life for all ages, and evidence shows that it is affecting 20% of the population.

Some people may be dealing with bouts of constipation and diarrhoea, where compacted stools may prevent colonic emptying — only watery stools can escape.

As the colon is involved in water balance, dehydration will have a more or less severe impact on the hardness of stools, and so constipation. Again, a diet low in dietary fibre may not provide sufficient bulk for regular stool formation. Food hypersensitivities to gluten, dairy and other specific foods can increase the likelihood of chronic constipation.

References:

1. Source: Biocare. (2018). Digestion in Practice.
2. Source: The Gale Encyclopedia of Medicine. (2015). 5th ed. Blackbirch Press.
3. Sharma, A. Rao, S. (2017). Constipation: Pathophysiology and current therapeutic approaches. Handbook of Experimental Pharmacology. 239: pp. 59–74