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. There is an abnormality in the transit time of ingested food.

Sometimes it is slower than normal causing constipation and other times it is faster causing diarrhoea. 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.
IBS symptoms can be triggered by certain foods. Just eating food stimulates intestinal muscle activity. This is a normal action and the most common is the Gastro colic reflex. This reflex is strongest after breakfast. Gastro-Colic reflex in IBS is strongest after fatty or large meals. This strong gut contraction can cause abdominal pains and or diarrhoea.

There is no evidence that food causes IBS but certain foods and the volume consumed at one time can trigger symptoms.

One suggestion is that the fault that results in IBS resides in the Nervous System. The gut has a complex network of brain cells called the Enteric Nervous System. This “Brain of the Gut” is connected to the Brain. Some researchers believe that to understand IBS, we have to understand the workings of the Enteric Nervous System.

The Gut has the richest supply of serotonin in the body. This chemical is closely connected to the nervous system. At present a lot of research is focused on gut serotonin receptors.

Serotonin affects the nerves in the intestine and controls contractions of the smooth muscles of the gut. Low levels of serotonin lead to constipation and higher than normal levels cause diarrhoea.

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. Statistics show that there is a greater incidence of psychological trauma and disturbances in IBS. Addressing these issues may produce 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. Gastroenteritis results in inflammation of the gut lining resulting in an overproduction of serotonin. In the thirty percent that develops IBS, the serotonin imbalance continues.

In some women, symptoms fluctuate during the menstrual cycle. The two hormones that control the menstrual cycle are oestrogen and progesterone. The passage of food residue along the large gut is affected by the female hormones.

Prof. Jonathan Brostoff of Middlesex Hospital believes that yeast is involved in some cases of IBS. An overgrowth of Candida occurs when there is reduced levels of good bacteria, Lactobacilli and Bifidobactreia.