Running Doctor

http://www.runnersworld.com/article/0,7120,s6-242-301--13482-0,00.html?cm_mmc=nutrition-_-2010_05_06-_-nutrition-_-DIET%3a%20Digestive%20Issues

I will attempt to play "doctor" by collecting all of the factual (as factual as Google results are) data and opinions on problems during running such as "you need electrolytes to avoid cramping" and translate that into "cramping - possible electrolyte deficiency". Pretty easy, huh?
Muscle cramping, cessation of sweating, nausea - dehydration 

Muscle cramping and stomach discomfort - over-hydration and nutrient/electrolyte dilution in blood. The body can absorb 15-20 (27) oz of fluids per hour

Muscle cramping, weakness, nausea - especially in hot weather - lack of electrolytes (calcium, magnesium, potassium, sodium (in the form of sodium chloride), and manganese).

Fatigue - too much protein, causing an overabundance of amino-acids in the blood, which are converted to dioxide, water, and ammonia; while excess ammonia is toxic to the body; not enough protein (for 90min+ exercises), causing the body to use muscle as a protein source and increasing ammonia production. During endurance workouts 8-15% of consumed calories should come from protein, the rest from complex carbohydrates.

Burst of energy followed by fatigue, mood swings - too much simple sugar in diet causing an insulin spike followed by a crash.

Bloating, nausea - too much solid food during exercise stresses the body requiring additional energy for digestion.

Slow muscle recovery, weak immune system - not enough calories consumed to make up for energy required for training. During an endurance race the body's requirement is ~200-400 kcal per hour.

Irritability, restless sleep, elevated resting heart rate, inability to reach peak heart rate during training, fatigue several days in a row - over-training.

Links  
http://www.time-to-run.com/training/articles/10mistakes.htm