My DH has ADHD. back in the day when he was young he was diagnosed with a sugar intolerance. He barely passed school because although he could do the work very well, he disrupted the class and spent a lot of his schooling sitting in the corridor. Now though he is in a job with much responsibility and is very successful in what he does. He does a lot of activities that are both physical and intellectual as he can't sit still.

'Back in the day' his parents coped by putting him into every after school activity you could imagine. It helped to tire him out somewhat. He was on a modified diet, that was kept as natural as possible. He also got sent to the family dairy farm, where he milked before and after school! (Not something I would imagine you could do with your DS)