Have you looked into the Specific Carbohydrate Diet? I am doing it myself (less than perfectly), geared toward Crohn's and colitis, but it is supposed to help autistic kids, who all seem to have compromised gut and immune systems. No grains at all, baked good use almond flour instead, mostly non-starchy veggies, fruits, honey is OK if tolerated. Meats OK. Certain cheeses and homemade yogurt OK (I make goat milk yogurt.) Has to do with the molecular aize of certain carbohydrates and how long they take to break down. Worth a google if you haven't looked into it.