Are sports drinks really better than plain old tap water?

For as long as sports have existed, athletes have attempted everything from eating raw meat to drinking bourbon, all in an attempt to increase performance. While many of these nutritional strategies have failed, guzzling carbohydrate-filled sport drinks can boost exercise intensity and duration. That is, as long as you use the right ones at the right time and for the right exercise.

The Sports Drink Advantage

Sports drinks, which are generally a mixture of water, carbohydrates and electrolytes, are designed to combat three main reasons why you might not make it to the finish line: dehydration, depletion of carbohydrate stores and a drop in blood glucose. "Someone

who is exercising continuously or at a high-intensity for longer than 60 minutes could benefit from these drinks," says Monique Ryan, a sports dietitian and author of Sports Nutrition for Endurance Athletes (Velo Press, 2002).

Go longer than 90 minutes and add in some humidity to the mix, and the utility of these drinks is even greater. But not everyone should reach for sugar drinks over water. "When exercising for less than one hour or taking part in a moderate stop-and-go gym workout, you won't reap any real benefits from these drinks," Ryan says.

How They Work

Muscle carbohydrate (glycogen) reserves are limited. A 150-pound male will have roughly 400 grams of glycogen stored in the muscle. A 130-pound female will have about 300 grams. Muscle glycogen is our most important source of energy for exercise, but, during prolonged exercise, such as long-distance running, it can be depleted fairly quickly (about three to four grams per minute) resulting in a drop in performance. "The carbohydrates in sports drinks can slow down the depletion of these glycogen stores," Ryan says.

Also during exercise there is an increased uptake of sugar (glucose) from the blood into the muscles to produce the energy needed for muscle contraction. Ryan points out that when blood glucose levels fall too low, your ability to maintain intensity in your running, swimming or cycling can be diminished. "The rapid supply of sugar from sports drinks can help prevent this detrimental drop in blood sugar," she says. Their ease of digestion is also a boon to those of who cannot tolerate solid food during exercise.

The sugar, flavoring and sodium present in sports drinks make fluid more palatable and in turn can stimulate extra fluid intake over water. Why is this important? Because, just a 2 percent drop in body weight through sweating can impair your performance, especially as we age. "Sports drinks are designed to have just enough carbohydrates nutrition and sodium to increase fluid absorption through the small intestine," says Ryan. The bottom line is that sports drinks can actually help you rehydrate quicker than water.

What's In the Bottle?

Ryan recommends that the correct concentration of carbohydrates in your drink should be about 5 percent to 9 percent. "Anything higher than 10 percent can slow down the rate at which fluid is emptied from the stomach," she says.

A high concentration of carbohydrates cannot only cause stomach discomfort but also negatively effect hydration. This is why fruit juices are not a great choice during exercise for hydration as they typically have a carbohydrate percentage more than 10 percent. Fruit juices are also higher in fructose which is typically not well tolerated in high amounts during exercise. Most sports drinks will contain two or more carbohydrates such as sucrose, maltodextrin and glucose polymers. "Research shows that more than one carbohydrate promotes better absorption through the use of more transporters," Ryan explains.

To calculate the percentage of carbohydrates in a drink take the grams of carbohydrate per serving and divide this by the serving size in milliliters and multiply by 100. For example, Gatorade Thirst Quencher has 14 grams of carbohydrates in a 240ml serving. This means that it contains 5.8 percent carbohydrates (14 grams/240 ml x 100). Make sure that when you are using powders that you mix it correctly with water to ensure that your solution is not over or under diluted.

Sodium is added to these drinks to help offset what is lost in our sweat. However, if exercising for very long periods of time (e.g. marathon run, century ride), especially in the heat, or if you are a heavy sweater, the amount of sodium added to most drinks won't be enough. That's where the new endurance formulas come in. "With at least double the sodium they do a better job at preventing detrimental drops in blood sodium levels," Ryan says. At the same time, you won't likely receive any endurance benefits from other additions such as vitamin C, calcium, and B vitamins.

Some recommendations

Hammer HEED is my choice for best-tasting drink. Gatorade Thirst Quencher, Powerade and eLoad are other well formulated sports drinks. Gatorade Endurance and Powerbar Endurance are your best bets when in need of extra sodium.

Matthew Kadey is a Toronto-based dietitian and free-lance writer (www.fuelforlife.ca).