We successfully curbed my child's ADHD behavior by following the Feilgold diet. The main culprit was apples (think apple cider vinegar also and the number of foods which may contain it, listing only "vinegar" as an ingredient). Also noticed an effect from liquids in plastic bottles as opposed to glass. Never was put on any medications and is an accomplished adult with multiple degrees.
Strange that 50 years later they are just recognizing this.