In 1958, a salty-sweet beverage named Bengal Punch made its debut at Louisiana State University as the first sports drink (followed seven years later by Gatorade). Since then, a booming industry has sprung from this modest beginning. The drinks are everywhere, and there's no escape from their hyperactive advertising.
Putting aside for a moment the pitchmen's implied promises of superhuman athletic ability after just a few sips, it turns out that sports drinks do in fact offer the everyday runner some real benefits. Everyone's belly is different, though, and all bellies react differently to different drinks. To avoid any unpleasant suprises, be sure to experiment gradually with sports drinks during training and especially before using it during a flat-out race.
What do they do?
Among the chief benefits of sports drinks are the carbohydrates they provide to help the body replace the energy-producing glycogen a runner expends during exercise. In the days before sports drinks, some runners created their own kind of sports drink, carrying defizzed soda with them to get the same type of energy boost, a technique still practiced by many. The trouble with these makeshift energy drinks is simply that they often have too many carbohydrates. Drinks that have a concentration of more than eight percent carbos (and some sports drinks fall into this category) are more likely to cause upset stomachs than those with lower concentrations.
Those same carbohydrates, when in appropriate concentrations of six to eight percent, also help the body absorb the sports drink up to 30 percent faster than water. This, of course, is great when you have been pushing hard and need to rehydrate in a hurry. Beware, though, that the concentration of carbohydrates is not too high. Some sports drinks, as well as some sodas and juices, have a sugar content that actually slows absorption.
Finally, sports drinks contain electrolytes, such as sodium and potassium, that are lost with sweat. Sodium in particular is helpful in speeding absorption of the drink. While it is not at all clear that your body actually loses very many electrolytes during running, studies have shown that electrolyte-replacement drinks do cause the body to retain more fluid than plain water.
On balance, sports drinks do provide an energy boost and slightly faster fluid absorption than water (again, provided that the drink has the proper concentration of carbohydrates). They are most useful during or after long or unusually hard workouts. For runs and races under an hour, however, it matters little whether you have a sports drink or plain, old-fashioned water (except that water has no calories).
Home Brew
While there's no question that it's difficult to duplicate the fancy electrolyte engineering that you'll find in many commercial drinks, these simple home-brewed sports-drink recipes from Cool Running can give you a similar carbo and energy boost.
Dilute these to taste and stomach comfort:
CoolLemon
1 cup water
1 tsp. lemon juice
1/4 tsp. salt
4 tsp. sugar
CoolCran
3/4 cup water
1/4 cup cranberry juice
1/4 tsp. salt