A few months ago, after reading a bunch of stuff from Hammer Nutrition on the subject of protein cannabilization and long runs, I started trying their "Sustained Energy" product which has some protein mixed in with the carbs. This stuff is kind of a pain for me to use - I do my runs after work in the evenings and the mixed form of this stuff starts going bad after a few hours. So I fill a couple of dry gel bottles with the powder and leave it sit all day. Then, just before heading out to run, I add water and shake well. I played with this for 4-5 long runs, I think plenty to see how it works out.
Well, I have to say, I'm going to stop using it. Nothing against Hammer. And I'm sure this works well for manypeople, just not so well for me. First, I'd prefer to simply carry a gel packet than a belt and bottles, especially during a race. The belts wear on me after a while. Second, I just don't like the flavor of the mix. It's not bad, but it sure doesn't inspire me! Third, and this is the real issue, I think they leave me constipated for several days after a long run. The gels just don't do that too me.