Not that it is a question to be asked because somebody wants to avoid medicines. But it may be the case as like almost 50% of the cases IBS patients, who likes alternative ways than conventional medicinal treatment.
One of the structured approaches towards this is to practice yoga along with a good IBS diet. In fact, you can choose any technique of stress management and meditation of your liking.
It is always advisable to take expert guidance while trying out any option. As a general principle, an effective stress management and mediation technique along with good IBS diet can avoid medicinal intervention successfully.