search for powersam's post on insulin.
I can't drink vinegar because it flairs up my acid reflux.
As for glycemic index, I heard you can eat anything as long as you mix it with lower stuff at the same meal. Potatoes are very healthy, but you can't just eat a backed potato by itself. You should eat it with peanuts or something. Getting a little of everything at every mean is healthier than fruit for breakfast and vegetables at lunch. The reason body builders must eat 6 meals a day, among other reasons, is they can only absorbe 20-30g at a time. A cup of powdered protein will do you no good beyond the first 20 grams. Also, whey protein is absorbed fast, and some other proteins are absorbed slower. You need a mix of everything so you can get some nutrients when you need them, but not get them all at once, so you have some 2-3 hours later, until you eat your next small meal. This also means your stomach will be smaller. I snack whenever I want throughout the day because I never eat a large meal like breakfast, lunch or dinner. People who eat three meals and then snack on top of that are the ones who get fat, unless they run or lift a lot.