No one will give you a specific cause of Irritable Bowel Syndrome. Some experts think IBS is a Motility Disorder. A hyperactive or oversensitive gut is another possible cause of IBS. and the gut will react to changes influenced by food, hormones and stress.
With the typical chaotic bowel habit of IBS, it is not surprising that it is thought of as a motility disorder. The transit time from ingestion of food to excretion is abnormal.
In diarrhoea the transit time is faster and in constipation it is slower. IBS is generally divided into two groups, constipation predominant and diarrhoea predominant. In some cases constipation and diarrhoea alternate. Stools in IBS can vary from hard pellets to watery and unformed.
Some say there is a link between diet and IBS.
Certain foods will trigger IBS symptoms. Intestinal gut activity is stimulated by ingesting food. This is the Gastro-Colic reflex and develops in response to food entering the stomach. In IBS, large meals, fatty meals or just the wrong meal can trigger a very strong gastro colic reflex. This strong gut contraction can cause abdominal pains and or diarrhoea.
Food is not a cause of IBS but can trigger symptoms.
One suggestion is that it is a brain-gut disorder. The Enteric Nervous System is a complex interconnection of brain cells in the gut. Some researchers believe that to understand IBS, we have to understand the workings of the Enteric Nervous System.
The highest level of serotonin, a neuro-chemical is found in the gut. At present a lot of research is focused on gut serotonin receptors.
Contractions of the smooth muscles of the gut are affected by serotonin. High serotonin levels are found in diarrhoea and low levels in constipation.
Psychological factors such as anxiety, stress and depression can affect the gut. In addition psychological trauma such as physical, emotional and sexual abuse can affect the gut. In IBS, records show a higher incidence of such trauma. It is suggested that in addition to treating the IBS, treating the other issues will give better long-term results.
Gastroenteritis as a cause of IBS: IBS can develop is 20-30% of cases of severe gastro-enteritis. The common infective organisms are Campylobacter jejuni, Salmonella shigella, and Escherichia coli. Serotonin levels in gastro-enteritis is very high and in cases that develop IBS this high level continues.
In some women, symptoms fluctuate during the menstrual cycle. The two hormones that control the menstrual cycle are oestrogen and progesterone. These hormones can affect the colon and the passage of residue along the gut. In some women IBS is worse at certain stage of their cycle.
Yeast according to Prof. Jonathan Bostoff of The Meddlesex Hospital could be a possible cause of IBS. These patients have reduced levels of friendly bacteria, Lactobacilli and Bifidobacteria in their large bowel. This results in overgrowth of Candida.