Whoa! Type I diabetics do well on a lower carb diet. It's not ketones they need to worry about but ketoacidosis.
Several writers, Bernstein and Schwartzbein come to mind, fully endorse a lower carb diet for diabetics. Unfortunately the majority of the medical folks do not and are still following the old rules. My doctor is finally convinced that lower carb works for me - he can't argue with my blood tests, can he?
I doubt very much that the nutritionist will buy into a lower carb diet BUT try to convince your grandfather to chose only good carbs, that is low GI carbs. Even the nutritionist will agree with that.
Books to check out - The Schwartzbein Principle and Dr. Bernsteins Diabetes Solution.
Here's a website (in a rival forum - so shoot me Suzanne!) that deals with diabetes and low carbing.
http://forum.lowcarber.org/forumdisplay.php?f=45. There is lots of other info for you on that site as well.
I wish you luck in trying to change entrenched ideas!
My stats? Before low carbing - HA1C was 7.7. Now it's 5.8 !