La diarrhée chez l’adulte


Diarrhea is not a digestive illness in itself, but rather a symptom of an underlying illness. It usually involves the sudden and frequent passing of watery stools. Diarrhea can cause a significant loss of fluids and electrolytes (eg sodium, magnesium, chlorine, potassium), sometimes associated with dehydration. It may be accompanied by abdominal and perianal pain, gas, cramps, incontinence, weakness, nausea, vomiting and fever.


Diarrhea can be acute or chronic, depending on how long it lasts. Acute diarrhea lasts less than a week and its most common causes include viral, parasitic or bacterial infections (eg gastroenteritis) and food poisoning. Chronic diarrhea lasts more than four weeks and its most common causes include irritable bowel syndrome and Crohn's disease.


There are four classes of diarrhea, depending on their cause:

Osmotic diarrhea

Osmotic diarrhea results from the consumption of substances that are poorly or not absorbable. When these substances are present in excess in the intestine, they retain water, which leads to the evacuation of watery stools. Some causes of osmotic diarrhea include carbohydrate malabsorption (e.g. lactose intolerance), excessive consumption of poorly absorbable carbohydrates (e.g. fructose), magnesium (e.g. laxatives, antacids), and laxatives containing the elements. poorly absorbable (eg: phosphate). Finally, osmotic diarrhea ceases with fasting or avoiding the offending substance (s).

Secretory diarrhea

Secretory diarrhea is characterized by the excessive secretion of water and electrolytes from the intestine. The causes of secretory diarrhea include bacterial agents (e.g .:E. coli), bile acid malabsorption (eg: in case of intestinal resection), malabsorption of long chain fatty acids (eg: steatorrhea), certain laxatives (eg: castor oil), a hormonal disorder and chronic alcohol ingestion. This class of diarrhea continues despite fasting.

Exudative / inflammatory diarrhea

Leaky or inflammatory diarrhea is secondary to various factors that can affect the intestinal lining, such as Crohn's disease, viral infections, parasites, or radiation therapy. The secretion of plasma, serum proteins, mucus and blood from the intestine increases the bulk and fluid content of the stool, causing diarrhea.

Diarrhea due to accelerated transit

Diarrhea caused by accelerated transit results from the reduction in contact time between digesting food and the absorption surface of the intestine. Decreasing the contact time reduces the amount of fluids absorbed from the intestine, leading to diarrhea. Accelerated gastric emptying can be caused by a number of factors, such as irritable bowel syndrome, resection of part of the intestine, and certain medications.

Nutritional approach

The nutritional treatment of diarrhea in adults aims to correct water loss and restore electrolyte balance, to find and eliminate, if possible, the cause of diarrhea, to prevent recurrence and to prevent and correct nutritional disorders and weight loss in chronic diarrhea. In general, the correction of hydration and the reestablishment of electrolyte balance is done using a rehydration solution, whose composition (water, carbohydrates, electrolytes) and the route of administration (e.g .: oral or intravenous) depend on the individual's state of hydration (eg: mildly versus severely dehydrated). Then, the dietary recommendations depend on the type of diarrhea (acute or chronic), its classification (eg: osmotic, secretory, inflammatory) and the underlying disease at its origin (eg: Crohn's disease, L's syndrome. irritable bowel, celiac disease, etc.). For example, for acute diarrhea occurring as part of gastroenteritis, dietary recommendations may include:

  • Start with a fiber-restricted diet and gradually progress to a normal diet
  • Eat several small meals a day
  • Pay attention to lactose consumption (secondary lactase deficiency is possible)
  • Observe a diet without excess of concentrated sugars (e.g. polyols, fructose, sucrose)
  • Consume probiotics, especially if gastroenteritis is caused by bacteria, such as hard, or following antibiotic treatment.

Finally, it is possible that the frequency of bowel movements continues to increase during treatment and it may take a few days before the stools return to their normal appearance. For chronic diarrhea, dietary recommendations are more extensive depending on the underlying disease (eg irritable bowel syndrome or celiac disease). Finally, in order to obtain recommendations tailored to your specific needs, do not hesitate to consult a healthcare professional who will be able to individualize his treatment to your particular case.



- Bouthillier, Lise. January 2019. Diseases of the digestive tract. NUT 2047 Clinical nutrition 2. Montreal: University of

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Article written by:

Marie-Noël Marsan, Nutritionist

Maladies digestives

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