Having the Natropath remove Charlotte from foods like nuts and
tomatoes, and sugar (high carbs/ potatoes) sounds like he's
suggesting removal from salicylates and / or sugar. Salicylates have
been known in some people to cause behavioral problems (My daughter
has some of these troubles), while sugar excess can be trouble for
other people.
Some Links for more info on salicylates/ behavioral problems linked to foods
  is http:www.feingold.org
http://www.sameboat.org/drrapp/DrRapp.html
http://allergies.about.com/cs/salicylate/index.htm

http://www.schoolnet.ca/sne/e/NCCS/rapp-01.htm