I hear that the modern thinking is not enough roughage over the years, and not enough 'healthy' type foods, as in raw fruit and raw and cooked vegies, can be the basic cause saxo_boi. (in certain people that is).
Many people get a roughage supplement from health shops to help get back to a normal state.
When you already have the condition and you eat foods with lots of roughage in them, the initial effect is that you may be running to the toilet for a while. Many people go off the very foods that will fix the problem in time, because they think it is making the condition worse....This is why some start the gentle way by getting a supplement, and then gradually increase the roughage diet wise, one thing at a time.
Of course if you are already, and have been always eating lots of raw foods and wholemeal bread etc then what I have said does not count with you. There could be another factor. Maybe you are short of enzymes in your system. (If you live on cooked foods only, this could well be the case). You can buy enzymes from the health shop, you would need one that covers all types of food. Proteins, starches and dairy products. Raw fruit and veg have their own enzymes and are not a problem. Hope this is some help and hope you find your answer.