This app was mentioned in 2 comments, with an average of 1.50 upvotes
I'm not sure if self-promotion is OK here, but I'm an IBS sufferer and author of Food Diary on android. I wrote it because I couldn't find a good solution at the time (and I wanted to learn about android development). Needless to say, that's the one I recommend, and I'm more than willing to answer any questions about it here.
I actually just got this one today https://play.google.com/store/apps/details?id=com.geoffholden.android.fooddiary
I was looking at all the free ones but this one seems so simple and quick to use, I didn't want anything too complicated. Just something for what I'm eating, when I eat it and any symptoms throughout the day. You can also add more categories if you wish. I'm very happy with it so far.