In simple terms, diarrhoea is an increase in the number of times an individual goes to the toilet or an increase in the amount that is excreted. It is a very common gastrointestinal symptom and one that can be uncomfortable, inconvenient, and even embarrassing for some, but it can also lead to the malabsorption of nutrients, and in extreme circumstances, to dehydration.

Believe it or not, diarrhoea comes in different types; osmotic diarrhoea, secretory diarrhoea, diarrhoea associated with deranged motility and inflammatory diarrhoea.

Osmotic diarrhoea occurs when the contents passing into the large intestine contains excessive amounts of solutes. This prevents water being absorbed from the intestine; instead it stays in the intestine and causes diarrhoea. This type of diarrhoea can result from the malabsorption of food or from the ingestion of a poorly absorbed substance such as mannitol or sorbitol.

Secretory diarrhoea occurs when there is either reduced absorption or excessive secretion of fluids and electrolytes. This can be due to the presence of toxins produced by various pathogenic bacteria or certain hormones.

Motility-related diarrhoea can happen when food moves through the digestive system too fast (rapid-transit) or too slowly (slow-transit). In the case of rapid transit, due to a health condition such as hyperthyroidism or a medication, the digestive system has inadequate time to absorb water resulting in diarrhoea. In slow-transit diarrhoea, osmotic or secretory diarrhoea can occur due to bacterial overgrowth and malabsorption.

Inflammatory diarrhoea occurs when there is damage to the mucosal lining of the intestines. This can be due to bacteria, virus or parasitic infection or to inflammatory bowel disease (IBD). Such damage makes water absorption ineffective and diarrhoea results.