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1Traditional Medicine Research  2019, Vol. 4 Issue (3): 140-147    DOI: 10.12032/TMR20190225100
Special Issue on Persian Medicine     
Digestion process and causes of indigestion based on Avicenna's view and modern medicine
Ali Reza Derakhshan1, Mahdi Yousefi1, Sohrab Dehghan2, Arman Zargaran3, Mahmood Khodadoost4()
1Department of Persian Medicine, School of Persian and Complementary Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
2Department of Traditional Medicine, School of Traditional Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
3Department of History of Medicine, School of Persian Medicine, Tehran University of Medical Sciences, Tehran, Iran.
4School of Traditional Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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This manuscript reviews digestion process and the problem of indigestion from the perspective of Avicenna and aims to establish a link between the perspective of Avicenna and the evidence of modern medicine.


Avicenna (born 980, died 1037, Hamadan, Iran) is regarded as the most distinguished Persian medical scholar. His masterwork Canon of Medicine became the mainstream medical system in the west until 17th century. Avicenna paid a lot of attention to gastrointestinal disorders and his view was based on the humoral theory.


The process of food digestion is one of the most important physiologic processes in human body. In this review, we are seeking the views of Avicenna, the most distinguished Persian medical scholar about digestion and indigestion. Avicenna’s view was based on the humoral theory. Avicenna has focused scrutiny on the process of digestion. He divided this process into four phases including gastric, hepatic, intravascular and intra-organ digestion. A defect in any of these phases can lead to disturbance in other stages. Avicenna approached the problem of indigestion through factors of diet, lifestyle and inherent structural characteristics of digestive organs. Modern medicine confirms Avicenna's opinion about the start of digestion from the mouth, the role of the stomach in digestion and the role of the liver in the metabolism of foods. Overeating or eating certain foods, snacking between meals, eating variety of different foods together, intense physical activity, sexual activity after a meal, stress and sleep insufficiency are among factors that may be linked to indigestion in modern medicine viewpoints and also have been mentioned in Avicenna's teachings. It seems rational to consider the medical approaches recommended by Avicenna for future studies in the field of digestive disorders.

Key wordsPersian medicine      Digestion      Indigestion      Malabsorption      Avicenna     
Published: 04 May 2019
Cite this article:

Ali Reza Derakhshan, Mahdi Yousefi, Sohrab Dehghan, Arman Zargaran, Mahmood Khodadoost. Digestion process and causes of indigestion based on Avicenna's view and modern medicine. 1Traditional Medicine Research, 2019, 4(3): 140-147. doi: 10.12032/TMR20190225100

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Avicenna's view Modern medicine's view
Gastric digestion Digestion begins in the oral cavity with crucial role of chewing and saliva.
Food is transformed into a semifluid substance called Chylus.
In addition to stomach, the liver, the spleen and the diaphragm have a role at this stage.
The role of the pancreas is not expressed explicitly by Avicenna, although he may have considered the pancreas as part of the spleen.
Mechanical and chemical digestion begins in the oral cavity with the effect of chewing and salivary amylase and lipase.
Digestion (specially proteins) continues at this stage with a key role of gastric juice and pancreatic enzymes.
Role of liver in this stage can be explained by the release of bile from gallbladder.
Dysfuction of spleen can lead to dysfunction of other digestive organs by dysregulation of immune system as well as gut associated lymphatic tissue dysfunction.
The diaphragm can play a role in digestion process in some cases by increasing intra-abdominal pressure.
Hepatic digestion The blood passes through Masariqa (mesenteric) and Baab (portal) veins and distributes in the liver.
The hepatic digestion leads to metabolization of food and formation of four humors.
These humors enter a vessel that emerges from the convex part of the liver and join the body circulation.
The superior mesenteric vein collects blood from small intestine and forms the portal vein in combination with splenic vein. Portal vein carries blood from gastrointestinal tract to the liver.
Liver process the blood, break down, and metabolize the nutrients. The blood that enters the liver is drawn into the sinusoids and after metabolization enters into the inferior vena cava via hepatic vein.
Intravascular digestion Occurs in the blood vessels.
Prepares humors for consumption in tissues.
Enzymatic reactions inside vessels such as endothelial lipase and protease activities can be considered as evidence of intravascular metabolism and digestion.
Intra-organ digestion Digested food reaches the tissue and digestion completed in each tissue specifically. The result is tissue growth and regeneration Intracellular enzymatic reactions and degradation and catabolism of food molecules can match this opinion.
Table 1 Four stages of digestion from the perspective of Avicenna and the evidence of modern medicine
Causes Avicenna’s views Modern studies
Intra-abdominal causes Structural abnormality or imbalance of humors in abdominal organs specially stomach, intestine or liver. Peptic ulcer, gastroesophageal reflux disease, gastric or esophageal cancer, pancreatic or biliary disorders, intolerance to food or drugs are considered as organic causes of dyspepsia [31].
Dietary factors Overeating
Inappropriate fasting
Eating foods which have high potential of rotting (i.e. fresh milk, fish and watermelon)
Eating a variety of foods in one meal.
Eat before digestion of the previous meal
Not following the right order of eating
Eating large amounts of food at a meal is effective in inducing indigestion [33].
Fatty foods, spicy foods, carbohydrate-containing foods and some other foods such as pickles vinegar, soft drinks, grain, tea, salt, pizza, watermelon, red pepper, and macaroni are the foods that cause the highest exaggeration of symptoms in functional dyspepsia. In other hand, apples, rice, bread, caraway seed, honey, quince, and walnut can alleviate symptoms. Milk and dairy products were controversial in dyspepsia [34, 35] but they have been implicated as trigger for Irritable bowel syndrome [36].
Higher prevalence of snacking between meals have reported in patients with dyspepsia [37].
Differences in digestibility and absorption of commonly ingested short-chain carbohydrates can lead to exacerbation of symptoms in functional gastrointestinal disorders [38].
Any alteration in eating habits and diet can affect the overall function of the gut [13, 15].
Lifestyle factors Intensive physical activity after meals
Sexual intercourse after meals
Mental and emotional stress after meals
Bathing after meals (There is no study about the relationship between bathing and gastrointestinal disorders)
Drinking more or less than needed
Sleeping more or less than needed
Exposure to very cold or very hot or polluted weather
Regular physical activity is associated with lower symptoms in irritable bowel syndrome but endurance sports is associated with more gastrointestinal symptoms [34].
Excessive eating and drinking may result in greater hemodynamic changes associated with sexual activity [16]. Furthermore, it has been reported that large meals are a risk factor for death after sexual intercourse [39].
Stress can influences activities in the gut and lead to dysfunction of gastrointestinal system through disruption of homeostasis in the gut [13, 40].
Difficulty falling asleep or sleep insufficiency has been identified as a risk factor for dyspepsia [34].
Air pollution can change gut microbiota and immune function [41]. It also can be a potential trigger of IBS [42]. Specific alteration of rhythm in temperature stress produces somatic and visceral pains in IBS [43].
Table 2 Possible causes of indigestion: Avicenna's view and modern medicine
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