Change the include_all_helpers config to false in any environment where you want to apply the configuration. If you want the config to apply to all environments, change it in application.rb.
In Rails 3, actioncontroller/base.rb (around line 224):
def self.inherited(klass)
super
klass.helper :all if klass.superclass == ActionController::Base
end
So yes, if you derive your class from ActionController::Base, all helpers will be included.
To come around this, call clear_helpers (AbstractClass::Helpers; included in ActionController::Base) at the beginning of your controller's code. Source code comment for clear_helpers:
# Clears up all existing helpers in this class, only keeping the helper
# with the same name as this class.
E.g.:
class ApplicationController < ActionController::Base
clear_helpers
...
end