Experimentation is the best way to determine which foods and drinks your system can tolerate. Generally speaking, one has to be much more careful regarding food selection when the run will be fast-paced. For example, don't eat a big lunch if you're planning on doing a fast run later in the afternoon. Instead, have small snacks throughout the day. Also avoid eating meals high in protein or fat prior to hitting the roads.
Runners often develop stomach cramps by consuming sports drinks that are highly concentrated.
A solution to this problem is to chase these products with a cup of water. Water should also be consumed after using a gel carbohydrate supplement to reduce the chances of developing stomach cramps. Nausea Dehydration is the number one reason most runners experience nausea. Nausea is an important warning sign of heat injury and should be taken very seriously. To avoid what can be a life-threatening situation, stay well hydrated both before, and during the run.