I have a little different perspecitve on this issue. I HAVE ADD. Not adhd, no hyperactivity. I believe the hyperactive component is more common in boys.
I'm glad you are considering all your options- including meds. Since I know firsthand what life was like with and without meds, I know how HARD it is unmedicated. Its hard when everyone is telling you to sit still, pay attention, etc and you cant. People do not understand.
Since I'm an adult, I wasnt diagnosed until I was 12, as I dont think before then the disorder was really widely recognized. I was put on basic ritalin. I have since tried other meds, and always go back to ritalin. Back then, it was truly a life changing thing, going on meds. I went from a D student to an A student, like magic. I started liking school more, instead of dreading every day. Homelife got easier too, but the big difference was definitely school.
As an adult, now, I think about 50% of kids today are misdiagnosed, or something else is going on that is mimicing (sp?) true ADD/ADHD. So I'm glad you did explore other options such as diet. I think a big issue is ADHD kids spend too much time sitting. ALL kids spend too much time sitting, as the childhood obesity epidemic proves. If he's not getting up and moving, hard and fast, every single day, get him going. Michael Phelps has ADHD, its how he got into swimming in the first place, his mom told the coach to wear her son down every day so he didnt bounce off the walls at home.
Bottom line, try meds but dont stop with other treatments such as diet and exercise. Ritalin is a basic long used drug. I have never had a single side effect except peace in my brain. Good luck!