A review of the most popular carbohydrate and caffeine gels for endurance athletes
By Eric Anderson, M.D. Explorebigsky.com Health Contributor
Electrolyte (salt), carbohydrate (sugar) and water replacement during aerobic exercise lasting greater than one hour can improve athletic performance and decrease the risk of dehydration or hyponatremia (low sodium concentration).
The American College of Sports Medicine recommends that in general, athletes should consume about 500 – 700mg of sodium for every liter of fluid and 30 – 60mg of carbohydrates per hour during sustained aerobic activity. Water replacement during exercise depends on a variety of factors but most athletes should consume about .4 – .8 liters per hour during sustained exercise, with higher rates for warmer environments and lower rates for cooler environments. A variety of commercially products are available to help an athlete obtain the recommended balance of salt, sugar and water during exercise.
Here, I’ve reviewed one type of carbohydrate and electrolyte replacement product that’s popular among triathletes, cyclists and runners: the carbohydrate gel.
Carbohydrate gels are an excellent way to fuel your body and replace lost electrolytes during aerobic exercise. Most come in single serving packages and contain a carbohydrate source and electrolytes (mainly sodium and potassium). These gels are also available with varying levels of caffeine. In addition, some brands also contain a protein source, calcium or antioxidants. The data is not as convincing for other products often included in carbohydrate gels, with the exception of caffeine.
Caffeine is known as the most commonly used drug in the world and has been used by athletes to improve athletic performance for many years. Specifically, caffeine improves performance during prolonged moderate to high intensity exercise lasting greater than 30 minutes. Most studies have shown that the optimal dose of caffeine for improving performance during exercise is 3 – 6mg per kilogram of body weight. However, more recent data has shown a performance benefit with caffeine doses as low as 1mg per kilogram of body weight. So, a 175-pound individual (about 80 kgs) would have to consume about 80 – 480mg of caffeine during exercise to obtain a performance enhancing effect.
If you choose to use caffeine during exercise, begin with the lowest dose for your weight to minimize the chance of side effects. Levels of caffeine in the blood usually stay high for about three to four hours after ingestion and are mostly gone within six to seven hours. Intake should be about 30 – 60 minutes prior to exercise to ensure levels are high when the exercise begins. During longer events, consumption of caffeine during regular intervals has a similar performance enhancing effect to taking the entire dose prior to exercise. Contrary to popular belief, caffeine consumption during exercise has not been shown to have a negative effect on hydration status or heat tolerance.
All gels are not the same, so read nutrition labels to make sure the product is in line with your nutrition and electrolyte replacement plan.

I chose four brands to review based on a non-scientific survey called “what gels my friends use.” I asked this group of mostly competitive triathletes and cyclists about their preferred carbohydrate gels. The top four picks were Hammer Gels, Clif Shots, Gu and Power Bar gels.

Hammer Gel
Hammer Gels have 80 – 90 calories per package, 21 – 22 grams of carbohydrate and four amino acids (alanine, isoleucine, leucine and valine). These gels are also available in a 26-serving jug to be used in a flask container that can hold up to five gels. The carbohydrate source is a combination of maltodextrin and fruit juice. They contain only 20-35mg of sodium per package and are designed to be used with electrolyte replacement capsules called endurolytes (each capsule contains 40mg of sodium along with 25mg of potassium, 50mg of calcium, 25mg of magnesium, 1.6 mg of manganese, 6.6 mg og vitamin B6 and 50mg of L-tyrosine). They are also available with or without 25 or 50mg of caffeine per gel. There are a total of 10 flavors available. My favorite is raspberry.
Hammer Gels are very popular among racers due to the large size they come in. Racers also like the ability to adjust electrolyte intake using the endurolyte product. Their consistency is slightly thicker, but still thin enough to work well in a flask. They tend to be on the sweeter side due to their fruit juice and low sodium contents.
The company is based in Whitefish, and all the products are made in the U.S.

Clif Shots
Clif Shots have 100 – 110 calories per package and contain about 22 – 24 grams of carbohydrate. Made with up to 90 percent organic ingredients, their main carbohydrate source is organic maltodextrin and dried cane syrup.
The cool thing about these gels is they vary from 0 – 100mg of caffeine, depending on the flavor. So, you can decide how much caffeine you want according to where you are in a workout and how you like to fuel. The different flavors also vary in sodium levels, from 60 – 90 mg. Two flavors, chocolate cherry and double espresso, are available with 100mg of caffeine.
In general, Clif Shots have a very thick consistency and wouldn’t work well in a flask container. Vanilla is my flavor of choice.

GU energy gels have been around since 1991. They have 100 calories per package and contain 20 – 25 grams of carbohydrate. The carbohydrate source is a combination of maltodextrin and fructose. Like Hammer Gels, GU contains a blend of amino acids. The sodium content ranges from 40 – 55mg per gel, depending on the flavor. These gels are a similar consistency to Hammer Gels and work well in a flask. There are 12 flavors with up to 40mg of caffeine. My favorite is vanilla bean.
In 2008, GU produced the GU Roctane energy gels designed for ultra endurance events lasting greater than four hours. The carbohydrate source is still the same, and it still has 100 calories per package. The main differences are that Roctane gels have more branched chain amino acids, more histadine, caffeine and electrolytes. Roctane also contains Ornithine Alpha-Ketaglutarate, which reduces muscle trauma during prolonged exercise. These have a similar consistency to the regular GU energy gels and are available in six flavors. They’re about twice as expensive as any gel mentioned in this article (about $2.50 per gel versus about $1.25 for other gels).

Power Bar gel
Power Bar gels have 110 calories per package and contain 27 grams of carbohydrate; they’re made from a combination of fructose, a simple sugar, and the complex carb maltodextrin. This gel is unique in that it contains 200mg of sodium. It’s also available with or without 25 or 50mg of caffeine per gel. The nine flavors include raspberry cream and vanilla.
The Power Bar gels have a relatively thin consistency that works well in a flask type container for longer events. They have a salty aftertaste that takes some getting used to; however, I find that you don’t have to worry about additional electrolyte supplementation when using these, as compared to the Hammer gels.

Eric Anderson is a sports medicine physician with Rockwood Clinic in Spokane, Wash. A competitive Category 1 cyclist and avid alpine and nordic skier, he lives in Spokane with his wife and two daughters.

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