Really depends on what you are eating. Processed grains contain very little beneficial fibre and those grains are converted into glucose just after leaving your stomach and entering the small intestines. Wheat contains an enzyme that makes the intestine lining porous in a lot of people. That could be issue number one which is leading to IBS. Issue number two is that the microbes in your large intestines need to be fed. They love insoluble and soluble fibre. If you don’t feed them they begin to starve to death and as a last resort will eat the large intestine lining. Once again causes the gut to become really leaky. Not good for IBS. So my suggestion. Cut down on processed foods, especially grain based foods (bread, pasta, rice, biscuits cookies breakfast cereals etc). Increase you veg and fruit intake to increase your fibre. Lots of beans and legumes. Lots of nuts like almonds and walnuts.

Give it 2-4 months to see any sign of improvement, it may even get worse for the first few weeks as your good gut bacteria wage a war against the bad gut bacteria.

Good luck with it.