Science Feature -- June 2003
By Ken Ortolon
In 1965, researchers at the University of Florida began testing a beverage that combined water, carbohydrates, and electrolytes on members of the Florida Gators football team to see if it could prevent cramping and dehydration caused by hot weather and physical exertion. The drink they developed, which eventually became known as Gatorade, is credited with helping the team improve its endurance and go from a 7-4 record in 1965 to 9-2 and an Orange Bowl championship two years later.
According to the Web site of the company that now manufactures it, Gatorade proved so successful that it quickly became a fixture on the sidelines of the National Football League, as well as many other college and professional sports.
Today, sports drinks are a multibillion-dollar industry and are hyped on television by some of the biggest names in sports. In 2000, Gatorade alone had more than $2 billion in sales, and numerous competitors have cropped up to challenge for a piece of the market.
But do sports drinks really help prevent dehydration, or would athletes and exercise enthusiasts do just as well drinking water? The answer, according to a report presented to the Texas Medical Association House of Delegates in April, is, "It depends."
For rehydration after routine exercise, plain water works just fine, the TMA Council on Scientific Affairs report concluded. But for extended periods of exercise or exertion, sports drinks containing carbohydrates and electrolytes do help prevent dehydration and restore important minerals lost through perspiration, the council said.
"For long-term strenuous activity, there are some data that would suggest that sports drinks may be beneficial," said former Council on Scientific Affairs Chair Michael E. Speer, MD, the report's lead author.
Hype Versus Science
Questions about the value of sports drinks were raised in the House of Delegates in 2002 in a resolution sponsored by the Tarrant County Medical Society. That resolution expressed concerns about aggressive marketing of sports drinks and the unknown science behind them.
Dr. Speer says one Tarrant County physician gave the reference committee a "graphic demonstration of what he perceived were abuses" by one sports drink company in promoting its product to children. The physician wore multiple layers of clothing, peeling each off to reveal the sports drink company logo. He also brought in other logo items, such as a water bottle, and expressed doubts that sports drinks are beneficial.
However, despite concerns about marketing and potential over-consumption, the council found that carbohydrate-electrolyte solutions are beneficial, particularly during and after prolonged periods of intense exercise.
"Exercise of short duration does not require the use of carbohydrate-electrolyte solutions, and water is just as effective at preventing dehydration and maintaining electrolyte homeostasis," the report says.
However, the council also found that "utilizing a carbohydrate-electrolyte replacement fluid during prolonged exercise or work appears to provide better carbohydrate utilization and improve exercise intensity in comparison to water or no fluid intake." Additionally, the council said that during prolonged exercise, "ingesting an electrolyte replacement produces better hydration than water."
Dr. Speer says that for most physical activity it does not matter whether you drink water or sports drinks as long as you drink something to replace fluids. Both the American Academy of Pediatrics ( Table 1 ) and the American College of Sports Medicine ( Table 2 ) recommend that children and adults ingest water or solutions containing carbohydrates and electrolytes to maintain adequate hydration during physical activity.
The American Academy of Pediatrics recommendations for children include consuming "cold tap water or a flavored salted beverage . . . even if the child does not feel thirsty."
Similarly, the American College of Sports Medicine guidelines for adults say that during exercise, "athletes should start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all the water lost through sweating." They also say that "addition of proper amounts of carbohydrates and/or electrolytes to a fluid replacement solution is recommended for exercise events" lasting longer than one hour.
Scientists at the Department of Exercise Science at the University of Iowa recommend that such fluids should contain between 6 and 8 percent carbohydrates and electrolytes by volume. Dr. Speer says that most major brands of sports drinks fall within that level.
If a person is not losing significant amounts of minerals through perspiration, water is adequate because the additional electrolytes are not needed, he says.
"For baseball or for a pickup football game, assuming you're acclimatized to the heat, it really doesn't matter whether you drink water or sports drinks. But if you're losing a lot of sweat, say you're a marathon runner, that's a different story because then you're going to potentially lose a lot of minerals as well as water. And replacing those minerals with a sports drink is not a bad idea."
Another potential benefit of sports drinks, the council concluded, is in ensuring that individuals, particularly children, consume enough fluid during exercise to avoid dehydration.
The council said most studies of fluid and electrolyte replacement found that many children and adults do not meet their fluid needs during exercise. The data also show, Dr. Speer says, that children and young adults will consume more fluid if they are offered a flavored drink.
"If you're going to encourage children and young adults engaging in sports activities to drink fluids, remember that they will drink more volume of a flavored drink than they will plain water, if both are offered."
But the council warned that children and adults should avoid over-consumption of sports drinks. "Abuse of sports drinks may result in adverse effects," the report states. "One case of potassium-induced ventricular arrhythmia has been reported in a football player who consumed about five grams of potassium per day via the overuse of a hydrosaline drink."
"You can pick almost anything and take too much of it," Dr. Speer added. "But the usual use of sports drinks is not going to be harmful. The usual use of water is not going to be harmful. Either one can be used for outdoor activities where you're losing a lot of water." And, unless you really need the electrolyte replacement, water is cheaper, he says.
Ken Ortolon can be reached at (880) 880-1300, ext. 1392, or (512) 370-1392; or by email at Ken Ortolon.
Table 1. Heat Stress and Children
American Academy of Pediatrics recommendations regarding climatic heat stress and the exercising child and adolescent.
- The intensity of activities that last 15 minutes or more should be reduced whenever relative humidity, solar radiation, and air temperature are above critical levels. One way of increasing rest periods on a hot day is to substitute players frequently.
- At the beginning of a strenuous exercise program or after traveling to a warmer climate, the intensity and duration of exercise should be limited initially and then gradually increased during a period of 10 to 14 days to accomplish acclimatization to the heat. When such a period is not available, the length of time for participants during practice and competition should be curtailed.
- Before prolonged physical activity, the child should be well hydrated. During the activity, periodic drinking should be enforced: each 20 minutes, 150 mL (5 oz) of cold tap water or a flavored salted beverage for a child weighing 40 kg (88 lbs), and 250 mL (9 oz) for an adolescent weighing 60 kg (132 lbs), even if the child does not feel thirsty. Weighing before and after a training session can verify hydration status if the child is weighed wearing little or no clothing.
- Clothing should be light-colored and lightweight and limited to one layer of absorbent material to facilitate evaporation of sweat. Sweat-saturated garments should be replaced by dry garments. Rubberized sweat suits should never be used to produce loss of weight.
Used with permission of the American Academy of Pediatrics. Pediatrics. 2000;106:158-159.
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Table 2. Fluid Replacement for Adults
American College of Sports Medicine guidelines for optimal fluid replacement for adultsduring exercise.
- Individuals should consume a nutritionally balanced diet and drink adequate fluids during the 24-hour period before an event to promote proper hydration before exercise or competition.
- Individuals should drink about 500 mL (about 17 oz) of fluid about 2 hours before exercise to promote adequate hydration and allow time for excretion of excess ingested water.
- During exercise, athletes should start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all the water lost through sweating (i.e., body weight loss), or consume the maximal amount that can be tolerated.
- Ingested fluids should be cooler than ambient temperature (between 15 degrees and 22 degrees C [59 degrees and 72 degrees F]) and flavored to enhance palatability and promote fluid replacement. Fluids should be readily available and served in containers that allow adequate volumes to be ingested with ease and with minimal interruption of exercise.
- Addition of proper amounts of carbohydrates and/or electrolytes to a fluid replacement solution is recommended for exercise events of duration greater than 1 hour since it does not significantly impair water delivery to the body and may enhance performance. During exercise lasting less than 1 hour, there is little evidence of physiological or physical performance differences between consuming a carbohydrate-electrolyte drink and plain water.
- During intense exercise lasting longer than 1 hour, it is recommended that carbohydrates be ingested at a rate of 30-60 g per hour to maintain oxidation of carbohydrates and delay fatigue. This rate of carbohydrate intake can be achieved without compromising fluid delivery by drinking 600-1200 mL per hour of solutions containing 4 to 8 percent carbohydrates (g/100 mL). The carbohydrates can be sugars (glucose or sucrose) or starch (e.g., maltodextrin).
- Inclusion of sodium (0.5-0.7 g/L of water) in the rehydration solution ingested during exercise lasting longer than 1 hour is recommended since it may be advantageous in enhancing palatability and promoting fluid retention, while possibly preventing hyponatremia.
Used with permission of the American College of Sports Medicine. Med Sci Sports Exerc. 1996;28:i-vii.
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