I've been told the same as belleenstein by a couple of gastros - that Asacol has a very short life span, so you need to take it 3 times a day to keep the gut under control. I've never had to eat food with it.
I used to play around with not taking it, or taking less, because I felt just fine, but eventually, I didn't feel fine anymore. For me, I've learned that it's easier to just get into a routine of taking it on the same schedule, every day.
I used to take 3 Asacol, 3 times a day, but now I take 2 Colazal, 3 times a day.
I take Nexium because I have gastritis (or so the gastro says....even though he also said it would go away, but 7 years later, it's still here...). So perhaps the Nexium hides the affect of the Colazal - I don't know. I switched during a flare up because the Asacol wasn't dissolving - it was shooting right thru me, whole. I could probably switch back to Asacol now, though, because they are easier to swallow.