First off, there are three types of sports drinks available, which all contain differing levels of fluids, electrolytes and carbohydrates.
Isotonic – Fluid, electrolytes and 6 to 8% carbohydrate
Hypotonic – Fluids, electrolytes and a low level of carbohydrate
Hypertonic – Large Carbohydrate Concentrations
Now, the osmolality of a fluid is a measure of the number of particles in a solution. In a drink, these particles will comprise of carbohydrate, electrolytes, sweeteners and preservatives. In blood plasma the particles will comprise of sodium, proteins and glucose. Blood has an osmolality of 290 to 320mOsm/kg. Drinks with osmolality of 290 to 320mOsm/kg are in balance with the body’s plasma and are Isotonic. Hypotonic fluids however, have fewer particles than blood and Hypertonic fluids have more particles than blood. Drinking fluids with small osmolality like water for example, results in a fall in the blood plasma osmolality and decreases the urge to drink before an adequate amount of fluid has been consumed to replace losses from exercise.
Which is most suitable?
Isotonic – supplies a boost of carbohydrates and rapidly supplants fluids lost by perspiring. Isotonic liquids are the choice for the majority of athletes. The body’s main source of energy is glucose so it can be ideal to consume Isotonic drinks where the carb source is glucose with a concentration of ~6-8%.
Hypertonic – mainly for supplementation of daily carbohydrate intake normally after exercise to pad muscle glycogen reserves. In long distance events, high levels of energy are required and Hypertonic drinks can be taken to meet the tremendous energy drain. If used during exercise Hypertonic drinks need to be used in conjunction with Isotonic drinks to replace fluids.
Hypotonic – quickly replaces fluids lost by perspiration. Proper for athletes who need fluids without the boost of carbohydrates (ex. gymnasts and ballerinas).
An important fact that needs to be remembered is that the regular sweet-juice taste combination doesn’t extinguish thirst, so there will be the desire to keep drinking a sports drink long after water has lost appeal. A wide variety of colors and flavors are available. Sports drinks offer a carbohydrate boost, in addition to electrolytes which may be lost from perspiration, but these drinks tend to offer lower calories than juice or soft drinks.
How should I use sports drinks?
Drink a few gulps in the early stages of a workout. The goal is to prevent dehydration, not remove it. Begin with 8 ounces twenty minutes before you start exercising, then drink four to six ounces (half the volume of a can of pop) every 15 to 20 minutes; that should be enough for most types of exercise.
Are sports drinks worth it?
Many “isotonic” sports drinks boast to re-hydrate and re-energize, but any product containing calories will increase your energy levels. The best way to obtain calories is from the complex carbohydrates found in cereals, bread, pasta, rice, and potatoes. Few know this, but simple carbohydrates like sugar are the worst and least nutritional way to obtain calories. Like soda, sports drinks contain extremely large quantities of sugar, in some cases, as much as 20%!
Sports drinks of course contain caffeine, as well as aesthetic oriented additives to enhance color, flavor, sweetness and stability. These additives do not increase performance in any way. Although caffeine may give a sense of instant energy, it is a diuretic and is more likely to dehydrate than replenish fluids as one feels the urge to urinate. The most effective re-hydration beverage is a combining of fruit juice and water with a pinch of salt. For a fast upsurge of energy, try a snack on fruit such as a banana or dried apricots.
Sports drink can be bad for the teeth and potentially dangerous for diabetics due to the high sugar content as previously mentioned. They commonly contain citric acid. All acids have an erosive potential but the method of drinking will influence whether or not those acids affect the teeth. Sports drinks should be consumed as quickly as possible, preferably with a straw and not be held or swished around the mouth. Retaining drinks in the mouth will only increase the risk of erosion. Refrigerated drinks will have a reduced erosive potential, as the acid dissolution constant is temperature dependent. A lot of ingredients in sports drinks come with a cautionary of health hazards if consumed in large amounts. Although one dose of a suspected carcinogen (such as an artificial dye) may not harm you, repeated use through ingestion of gallons of a sports drink may eventually cause symptoms.
Recently, the American College of Sports Medicine condemned sports drinks and dismissed the idea that they are superior to water. Sports drinks are a waste of money, they only serve to compromise your health and performance. There are much better, natural alternatives to revitalize yourself.
Sources
http://www.pponline.co.uk/encyc/0813.htm
http://chemistry.about.com/cs/foodchemistry/a/aa070803a.htm
http://en.wikipedia.org/wiki/Sports_drink
