The cause of IBS is still unknown. IBS is a motility disorder some experts say.  A hyperactive or oversensitive gut is another possible cause of IBS. and the gut will react to changes influenced by stress, food and hormones.

Typically the bowel habit in IBS becomes chaotic. There is no surprised, therefore that it is considered a motility disorder. The transit time from ingestion of food to excretion is abnormal.

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. Some have diarrhoea and constipation alternating. In IBS stools 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. Intestinal gut activity is stimulated by ingesting food. This is a normal action and the most common is the Gastro colic reflex. This reflex is strongest after breakfast. 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.

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 it is a brain-gut disorder. The gut has a complex network of brain cells called the Enteric Nervous System. This “Brain of the Gut” is connected to the Brain. To understand IBS, experts think you need to understand how the Enteric Nervous System works.

The highest level of serotonin, a neuro-chemical is found in the gut. Significant research is currently done on the chemical and its role in IBS.

Serotonin affects the nerves in the intestine and controls contractions of the smooth muscles of the gut. High serotonin levels are found in diarrhoea and low levels in constipation.

Psychological factors such as anxiety, stress and depression can affect the gut. Trauma suc h as physical, sexual and emotional abuse can affect the gut. Statistics show that there is a greater incidence of psychological trauma and disturbances in IBS. 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. Escherichia coli, Salmonella shigella and Camplobacter jejuni are the most common organisms involved. 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. 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. An overgrowth of Candida occurs when there is reduced levels of good bacteria, Lactobacilli and Bifidobactreia.