In addition to our family dealing special diets and food allergies, we have also had to deal with learning issues and found that diet played a huge role in things.
Our oldest child had a complicated history but reached an age where he had been diagnosed with ADHD and was given several medications. They seemed to be more of a placebo for him and simply didn't produce results over time. Since we were very knowledgeable about food and how it affects the body, we decided to start our child on a gluten and dairy free diet. Within the first week, we saw a marked improvement in him. With him, we also experimented with the GAPs diet, Paleo, and Juicing. We saw the absolute best results from juicing. He told us that he had never been able to think to clearly or quickly. We also saw negative results in learning and behavior anytime he would go out with others and eat foods that were heavy in wheat and dairy (pizza, lasagna, etc.).
Our third child is also severely impacted by food. He had been (mis)diagnosed with ADHD, on the hyperactive side. He was physically assaulting other people and was truly a nightmare child (at age 5). He was medicated and the medication caused physical pain in his heart. After this happened twice, I was determined to find a better way forward for him. In his case, it was getting into trouble that was the saving grace. In our home at the time, dessert was always on the menu. We were introducing lots of new foods to our kids, and those who were brave and tried were able to have dessert. After getting into lots of trouble, his dessert was taken away for 30 days. This was like a death sentence in our home. After two weeks, we had a completely different child. The day his sugar came back, within two bites, he was literally bouncing off the walls. From there I tracked his intake and learned that 20 grams of added sugar was all he could handle, the equivalent of two children's snack bars. After that, we eliminated all chemicals, pesticides, food colorings, additives, etc. from his diet. He eats as organic as possible, always non-gmo, and his cane sugar intake is as close to zero as possible. On days where all added sugars come in at less than 10 grams, he says it's just so easy to think straight, and to behave himself. Now as a teenager, we find that the physical outbursts have resolved themselves, but he can have quick mood swings and become quite defiant if he's had something to eat that's not working for him.