putting laxatives in college meals

I am sure that my school uses laxatives. I ate in the dorms for one semester and started having problems with abdominal pain. This year, I stopped eating in the dorms and was diagnosed with IBS. My predominant symptoms are pain and chronic constipation. I have eaten campus foods several times since terminating my meal plan, and every time I do, I have a loose bm the same day (which is a real rarity for me because of the chronic constipation). I can't imagine another reason why I would suddenly have a loose stool every time I eat campus food unless they put laxatives in the food. Thus, I've abandoned campus food completely.