Diet change

We have been having some issues with Cade's behavior and I am at a loss as to what to do for him. The main problems we have with him is he has no sense of personal space. If we try to explain to him why personal space is important, he just doesn't get it. No amount of  talking or discipline gets it through to him. I've done some reading and research and I'm going to be changing his (and all of hour's!) diet. It will be a 6 week transition, each week focusing on something to eliminate.  This week, I will be getting rid of artificial coloring and flavors. I will be shopping tomorrow for new items to add to our diet that is free of these things! Any ideas for snacks for kids that have no artificial colors or flavors would be appreciated! I'll update later with what I found for him and how things are going!