A steady caloric intake is very important in running ultras, even more so as events get longer (100 miles and beyond). Over the period of a few months you should be able to find a number of foods and/or beverages that you handle well (no or little stomach discomfort), that taste good to you, and that are “packable” while doing your long training runs.

As to the rate of intake, try for about 300-400 calories an hour, which works out to maybe 12-16 ounces of a sports drink and an energy bar per hour. This is not a lot. Try to eat about every 30-40 minutes, as this keeps up your energy level without a lot of bulk for your stomach to handle at any one time. If you go with a mostly liquid food intake, try to take it at a rate of several ounces about every 20 minutes. Mix that in with some drinks of just water. If you handle solid food ok, there are lots of options. Sandwiches of various types, energy bars, fruit, pretzels (also for salt), and granola type mixes are good choices. Shoot for mostly carbohydrates, with maybe 20% of calories from fats and 10% from proteins. In the later stages of longer ultras (50 miles plus) you might get “tired” of the same old stuff and go to things like soup, energy gels, and supplimented drinks like Ensure that might be easier for you to digest.

So I suggest you try out a number of different foods and drinks on your upcoming training runs. With the 300-400 cal./hr intake you replace about 50% of the calories you burn, keep up your blood sugar, and allow for continued burning of stored fats which in long distance races is a significant fuel source. If you do encounter stomach troubles, there are a few things to try to combat this. These would include things like antacid tablets, going only with liquid intake, and trying to ensure your salt intake is adequate. For some, drinking milk or eating higher fat foods will help a sour stomach. One other thing to try is eating while you walk for several minutes, and to eat on uphills a ways before you get to longer downhill sections. Also consider that you might have more stomach problems in hot or humid weather, so plan accordingly for those types of races with regard to your drop bags and what is on hand at the aid stations.

Good luck with finding foods and beverages that work for you.

Taken from: Shawn McDonald’s UltraRunning Advice