DH was diagnosed with IBS about 18 months ago. His trigger was pork fat - and being the carnivore he was it was a big blow. Giving up his pork ribs nearly killed him!

He now has a lot less stressful lifestyle (quit his job and now at uni), is taking fish oil and probiotics daily and is eating a high vege and fruit diet. We also have cut out a lot of dairy in our house and everyone is getting more exercise.

It was very much a trial and error at the beginning, and he kept trying to have pork, but everytime he got very sick. We also kept a food diary (kind of) and when he had an attack we looked at all the foods he ate in the last 36 hrs. That is how we were able to narrow it down to pork.

Try the food diary idea as we found that it normally took over 18 hrs for the food to affect him and by that stage we had often forgotten what he had eaten. A bad attack would have an effect within 30-40 mins, but that was usually if he had eaten the food twice in one day.

Good luck with finding the triggers. I just asked DH and he said changing diet was the best thing he could have done.