Endurance sport friend, physician and vascular surgeon David Campbell came forward with some hard science on e-Gels. Check out his excellent summation:
Here is my 2 cents worth on the Crank gels. Personally I really like the stuff.
The amino acid idea is an interesting idea. Amino acids can be used to produce "energy" ( which is in biochemistry terms is ATP or adenosine triphosphate) via the Krebs cycle. The most effective fuel for making ATP is glucose or more commonly known as fructose. Glucose is stored in the body mostly as glycogen in the liver. As you know, most of us have about 2000 cal of glycogen available before our body must switch to alternative energy sources such as fats and proteins. Consequently, fructose supplements are just like having some additional glycogen on board. The limiting factor is how fast your bowel can absorb the fructose into your system.Crank's primary benefit definitely comes from having 150 cal of fructose in a easily packaged and easily consumable package.
The addition of amino acids is an interesting idea. Proteins are composed entirely of amino acids. Crank has an amino acid "blend" of leucine, valine, isoleucine andhistadine. I think this is what you refered to as GU-Roctane which is a pretty cool name for promotional purposes. The amino acids do not provide any real "buffering" capacity (ie neutralization of acids such as lactate from anaerobic metabolism) but the might cut down on the cannibalization of our own body proteins when we use up all our stored glycogen from prolonged exercise.
The addition of vitamin C and E work as antioxidants. Antioxidants neutralize oxygen radicals produced as cellular waste products. Vitamin B6 can be a energy booster but I can't recall the exact mechanism. I think on a practical basis you can get the same benefit from vitamin supplements prior to the event. The vitamins can't hurt but I wonder about their real benefit during a race?
Crank has no caffeine which is fine, but personally, I would like to see a product with caffeine as well like Hammer does. A nice caffeine jolt works for me after a couple hours of exercise. I was glad this "energy gel" does not have similar energy additives as found in Red Bull or Monster ( such as taurine). That stuff seems to have a detrimental effect on endurance performance in my experience.
The electrolyte composition seems pretty reasonable. The potassium is especially helpful for endurance events.
I have a good friend who is an anesthesiologist at UC San Diego and is also a big marathon runner. He is up on ALL the biochemistry stuff. I'll see if he has any other comments about Crank. I think he uses Hammer but I'm sure he would like to give Crank a try.
Aside from all the above, I gotta give credit to the Crank people on their marketing. No matter if the effect is real or perceived, they do a nice job of convincing you that you "need" their product.