An engineer friend, Derek Paice, came up with the idea of the "substance glycemic index," or SGI, which is essentially a GI but for all foods, not just carbs. He describes it in a free online booklet at http://www.mendosa.com/DiabetesAndDiet.pdf. Unfortunately, he's closed his website, which had some other information.
My idea was that there's tremendous power in the online community, and if there were a way for people to measure their own SGIs and then post them to TuDiabetes, eventually there might be enough data to help people who didn't want to measure their own.
For example, Derek measured the SGI of whole-wheat bread as 100, cheese pizza at 59, Kellogg's Bran Buds at 25, a Fugi apple at 19, steak at 17, cantaloupe at 12, cauliflower at 7, and cheese omelet at 6. He also measured a complete meal and found that the SGI of a meal containing steak, cabbage, Merlot wine, sugarfree gelatin dessert, 2 candies, and coffee with creamer had the same SGI (77) as 1.5 slices of whole-wheat bread.
The idea is that you eat a food or a meal and then measure the area under the curve (AUC) until it returns to baseline and compare that AUC with your AUC for a control substance, expressing it as a percentage. Derek used whole-wheat bread, but I think that's not a good control because the ingredients of whole-wheat bread can vary so much. Glucose would be better.
He used 60 grams of food, but one could use any amount. The point is to compare that food with an identical amount of the control food (bread or glucose).
The GI used 50 g of "available carbohydrate," not a certain weight of food, and some foods might have carbs with a high GI but not much carb. The glycemic load is supposed to correct for that, but you can't get GLs for foods for which no one has calculated GI, for example, meat and nonstarchy vegetables. I'm type 2, but meat can make my BG go up.
Also, GI only measured for 2 (nondiabetic) or 3 (diabetic) hours, and when you have type 2, you can stay high for longer than that, so measuring until you return to baseline makes more sense.
Clearly, this wouldn't work for anyone using bolus insulin, but knowing the SGIs that had been calculated by type 2s could help some type 1s with food choices.
Anyway, right now it's just a vague idea. I was wondering if anyone else thought it had merit.