Spreadsheet of the glycemic indices of 4,000 foods as measured by the NCI [xls]

The situation is much like with artifical intelligence in the early days - trying to boil the problem down to a few simple rules. Until we are willing to accept the huge complexity involved in the problem we do more harm than good. There is no single useful scale on which to judge foods. (See lukesandberg's comment and link below.)

In the meantime I recommend you eat like a caveman.

- meal GI can be lowered by simply consuming more protein/fat based foods, or high grain foods alongside the food.

- Studies of GI look at each food in isolation

- GI ignores the insulin index which surprisingly is not correlated that well with glycemic index, meaning there is more biologically at play than simply GI

- Lower GI is not correlated that well with healthier choices

Like everything else, it's not a silver bullet. "Eat unprocessed food that runs, swims, flies or grows" is a simpler diet plan and more likely to be good for us because that's what we evolved to eat, not how quickly does one food in isolation get metabolised compared to 100grams of dextrose.