Irritable Bowel Syndrome (IBS) is a term used to group an array of symptoms such as altered bowel movements, bloating, abdominal cramps, etc. The cause is rarely a single cause but rather an array of different factors e.g. stress, nutritional, lifestyle, mechanical, other health problems, etc. Due to its complexity it can persist for many years with each factor being reinforced. There is no one approach that has the answer, however different approaches (e.g. medicine, osteopathic, nutritional, lifestyle) can help reduce the symptoms.
The digestive system is made up of a group of organs located in abdomen (see diagram). The organs are loosely stuffed into a bag like structure and given some degree of freedom to slide around. This improves their function as well ensures they can absorb the forces generated by our movement. They are supplied by nerves originating from our spine and their blood supply comes from a large blood vessel (the abdominal aorta) which runs centrally at the back of the abdominal space.
For any organ to function properly it needs 3 things;
1) a good blood supply (i.e. its source of nutrients);
2) a good nerve supply so it may do as the brain commands and
3) freedom of movement.
How Structure affects Function
Let us assume you have a stiff or painful spine. The chemical environment generated by stiffness or pain can affect how the nerves function i.e. the quality of their impulses. If this occurs in the location of the organ supplying nerves then the organs will receive a poor quality impulse/command. Organs are like soldiers (they follow orders without question) hence they will do a poor job at digesting food.
Over time this can lead to problems. A stiff spine or a pain related posture may also affect the mobility of the organs, i.e. if your right lower back hurts you may shift your weight to the left which compresses the organs on the left side. Just like your joints or muscles, organs do not like to be still as it affects their function. An immobile organ is far less efficient than a mobile organ and so again we see the digestion process affected.