With the snow and ice, I have been on the treadmill and spin bike over the past couple weeks. I started thinking about nutrition during long runs. It is my opinion that any time you are running longer than an hour, you should have a half to 1 liter of water per hour. For runs longer than an 1 and half hours, you should use a goo or something of the sort. Beyond liquids, I personally like to have something solid, like a Clif bar, after the two hour mark. I find that after a couple of goos, I want something more in my stomach. Most people would say that they don’t want too much in their digestive system so that blood is not shunted away from the muscles, but I have not had that problem.
There are many different brands of goo, but two of my favorites are Hammer Gel and Clif. Basically, they are sugar and some electrolytes in a thickened liquid. Always wash it down with some water, or you will be tasting whatever flavor you chose for the next mile. There are some alternatives to the goo in the form of shot blocks and the like. They are basically large gummy bear consistency blocks. I don’t particularly like them because they get stuck in my teeth for about 5 minutes. They are nice if you hate the consistency of the goo. Some people like to take a half of a goo at a time and space them out over a longer period of time. In this case, especially if you are wearing a water belt, you might want to consider a goo bottle. 5 goos will fit in the bottle, which should be enough for the whole race.
The bottom line is go to REI and buy a few different flavors and types to see which one works for you. Part of your training is learning which nutrition works well for you in terms of taste, consistency, and digestibility.