This is the kind of book that should answer a lot of those questions about what foods contain gluten and what foods are beneficial, and why? It's especially useful for any parent with children on the Autism Spectrum and looking at the positive and negative impacts of certain foods - the dietary interventions.
We went this route with our children years ago as we realized that dietary interventions produced positive results with our family. We wish there had been a resource like this available to help guide us.
You can grab a Kindle version online for a reasonable price. And yes, that is an affiliate link, but as I repeatedly note on this blog, I'll only promote products that I've tried, used and personally endorse. This is a good book and worth reading - whether you buy it or not.