The first step to healing the gut is to reduce inflammation. The best way to know what foods are causing you inflammation is the autoimmune protocol diet (yes, even if you do not have an autoimmune disease!)
Here's why: The goal of the IPA diet is to reduce the amount of inflammatory foods in the body so that a.) your gut can begin to heal and b.) so that you can figure out what your body is actually intolerant or allergic to.
Then, you add in one food group at a time slowly, making note of how you feel. If you don't feel good after adding in a food group, take it back out and make note of it so you can avoid those foods while you focus on healing.
EVERYONE'S INFLAMMATION STRESSORS ARE DIFFERENT!
This diet will help you eliminate which ones are causing YOU issues while keeping in other foods that are fine for you but might bother someone else! This means, you may actually end up eliminating less than you might otherwise.
The hope is that you won't ALWAYS have to avoid all the foods that are making you hurt...but to give your body time to heal first so that those food groups won't bother you when your gut is completely healed.
I would suggest anyone who is having gut issues, do the Autoimmune Protocol diet because then you can figure out what foods you are intolerant to/allergic too without paying for an allergy test which is most likely going to change as you heal your gut anyway.