One thing that Jeff Novick has mentioned is that when he worked at the Pritikin Longevity Center, they took thousands of diabetics off of their diabetes medications using diet and exercise and they never used the glycemic index.
Dr. McDougall's program for getting diabetics off of their medications is similar to (and if anything, stronger than) Pritikin's program.
Here's my question: Has their ever been a controlled trial in which 100 diabetics followed the McDougall (don't worry about the glycemic index) diet and 100 diabetics followed an alternative diet that did concern itself with the glycemic index?
Until I see a head to head matchup like that, I don't think diabetics should be overly concerned about the glycemic index. That said, I am not currently diabetic and I am not a doctor. So, what do I know?
Oh, one more question.....
At the McDougall programs, do they test postprandial blood sugars in order to guard against spikes in blood sugar given that they serve some high glycemic food there?
If they don't and they have great success in getting diabetics off of their meds, what problem are we trying to solve with this glycemic index?