There is a optimum concentration of sugars for energy drinks while riding. Too much sugar and you slow the absorption of water, too little and you slow the absorption of carbs. I don't remember the proper ratio.
Carb absorption/processing to replenish glycogen reduces significantly above 75% of max (measured) heart rate.
Contrary to the popular media, you do not always get an evil insulin spike after consuming sugar. If you're exercising at a reasonably rigorous level, your insulin sensitivity increases which means that your cell walls become more porous to glucose and you do not produce more insulin. The affect apparently continues for some hours after vigorously exercise and might be the basis for the 4 hour post-ride window for carb loading to speed recovery. I suspect it's also the reason that lack of physical activity is often cited as a reason for type 2 diabetes.
However, a sugar drink before a ride will likely induce an insulin spike, but it's not clear to me at least, that it matters in a well exercised individual with a decent overall diet.
Source: Exercise Physiology; Exercise, Performance and Human nutrition, 6th edition.
A consideration for going "natural" is that fructose (which is high in many fruits and is 50% of sucrose(table sugar)) is processed differently than other sugars as it goes thorough the liver. It's therefore a very slow process to convert sucrose to glucose. You won't get a fast boost from some fruits to avoid glycogen depletion.
The devil is in the details.
Al
Last edited by alcanoe; 03-15-09 at 04:14 AM.