Nutrition and ADD

My husband was diagnosed with ADD 3 years ago.  He has gone his whole childhood and on his 3 marriage and just found out he has it.  It wasn't until 2 months ago that I realized we needed to get really real with this condition.  Our marriage has been a nightmare for 11 years.  It is amazing what we are learning about the condition and how everything that has happened has been all because of his ADD.  It is all making so much sense now.  He is still taking it all in  and everyday gets better with him accepting he has it.  We are now working on putting together a treatment plan for him so things can run smoother for him and his family. My first question is nutrition.  He consumes a lot of sugar.  How bad is that on someone with ADD?