Carbohydrate type
There appears to be no major difference between glucose, sucrose, maltodextrins and starch on athletic performance. However sports drinks that contain mainly fructose may cause GI distress due to the fructose's slower absorption rate.
Read labels carefully; look for a combination of these carbohydrates. Fructose is sweeter than maltodextrins and is often used to make the drink more appealing. Maltodextrins remove the unpalatable sweetness, and sucrose is absorbed more rapidly than fructose.
Carbohydrates, regardless of whether solid or liquid, will aid in athletic performance. Consider drinking them rather than eating them, since fluids take care of two very important performance issues: hydration and energy.
Ergogenic aids
High doses of vitamins and minerals -- and some ergogenic aids, such as creatine or caffeine -- may cause GI distress. Creatine has recently become one of the most popular ergogenic aids marketed to athletes. Some studies have shown creatine supplementation may promote gains in strength, performance and fat-free mass, either due to increased muscle mass or water retention.
While not all studies report ergogenic benefits, most studies warn about the dangers of incorrect dosing. There are also concerns about muscle cramping, increased muscle injuries and, of course, GI distress.
Although ingesting a carbohydrate drink with creatine has been shown to increase muscular creatine accumulation, it also increases water retention. The risk of developing GI distress is thus increased when combining sports drinks with ergogenic aids.
In summary
GI distress may be an individual adversary. It's important to experiment to find out which sports products work best for you. Water is a good drink if exercising for less than one hour. Carbohydrate/electrolyte drinks, such as Gatorade, are good for endurance and high intensity training because they are absorbed at optimal rates.
Water provides no flavor or electrolytes -- factors which cause athletes to want to drink, and therefore, keep them hydrated. Water provides no energy, while sports beverages contain carbohydrates, which help athletes provide their muscles with the needed fuel to avoid early fatigue and poor performance.
The sodium provided by sports beverages helps athletes maintain blood volume, a factor critical to maintaining sweat rates and performance. Sweat contains sodium that water alone cannot replace.
However, to prevent GI distress, these fluids should not be more than six- to eight-percent carbohydrate-concentrated (approximately 14 grams of carbohydrate per eight oz); they should have a mixture of sucrose, glucose and fructose; and they should provide a minimum of 100 mg sodium and 28 mg potassium per eight oz servings.