To take a stab at answering the question asked a few posts back about the speed of repletion of potassium:
Potassium distributes through the entire body water fairly readily. Body water comprises approximately 70 percent of an adult human. Therefore, the standard "70 kg man" has about 49 kilos of water, or 49 liters (call it 50). Normal potassium levels are between 4 and 5 meq/dl, and nobody's going to be symptomatic above about 3, so let's say the cramping person is down 1 meq/dl. That's a total body deficit of 500 meq. There are about 400 mg of potassium in a banana, or roughly 10 meq. Therefore, you'd have to eat 50 bananas to replete total body potassium deficit.
You could argue that simply pushing the potassium levels in the blood up would do it, which would require less, only about ten bananas. Except the cramping is occurring at the muscle cell level, which is intracellular potassium, so you have to get the mineral out of the eaten banana, into the blood and then into the cells. Potassium transport is not by simple diffusion, so it's not entirely gradient-driven, and requires the proper milieu (pH, glucose, etc.) to occur.
So what I'm trying to say is that a) potassium deficiency is rarely, if ever, a cause of cramping muscles, and b) eating a banana if you're having cramps is not going to make them go away.
Muscle cramping can be a symptom of significantly abnormal mineral levels (eg. calcium) but again, this does NOT occur in people who healthy and are not experiencing unusual fluid losses.
