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The feed zone - Nutrition Q&A with Monique Ryan - Tracking the glycemic index

Published: Apr. 28, 2004

Dear Monique,
I have heard a lot about the glycemic index. There seems to be no low glycemic index sports drink on the market. I know that Gatorade is high glycemic, and that fructose is low glycemic. Wouldn’t a fructose only sports drink be better (provided it had the right balance of electrolytes)? It would be low glycemic and work for diabetics, and not raise insulin or blood sugar levels like sucrose. Wouldn’t this be a better alternative than a high glycemic product? I have heard some negatives things about fructose in relation to tolerance. Also, how important is the 4- to 8-percent solution I’ve always heard is necessary in a sports drink?
Thanks,
BTDear BT,
Your question regarding glycemic index of sports drinks is a timely one because of all the discussion and ongoing research on glycemic index in regards to both health and athletic performance. Your question specifically addresses the issue of glycemic index considerations in regards to carbohydrate consumption during exercise. One of the most recent developments in the sports nutrition industry centers on the type of carbohydrate provided, and more specifically the glycemic index of these drinks. Some of the newer products have a lower glycemic index with the promise of keeping blood glucose levels even and steady. First, it is really important that sports drinks fall in a 6- to 8-percent carbohydrate concentration range as this allows them to empty from your stomach quickly and be absorbed through your small intestine, while providing carbohydrate for energy. You are more likely to match your fluid losses with a well-formulated sports drink, and they also provide sodium to help replace sweat losses and stimulate your thirst mechanism. Once you become dehydrated, fluids empty from your stomach more slowly. Many cyclists and triathletes need a change of taste when training and competing, and gels provide a semi-solid answer to this dilemma. Gels are also formulated from various carbohydrate sources and are highly concentrated when compared to sports drinks at 65 to 70 percent. Once gel packet should be consumed with at least 16 ounces of water. One advantage of sports drinks is that they provide sodium, which can help replace sodium sweat losses, and also stimulates your thirst mechanism. The carbohydrate in sports drinks can also give your immune system a boost, by decreasing the immunosuppression athletes experience in the hours after training.Below are a couple of tables that provide the glycemic index of various carbohydrate sources, and the glycemic index on sports drinks that have been tested for this data. Some products may consist of carbohydrates from lower glycemic sources, but have not been measured for glycemic index as a product. As the table indicates, fructose does have a low glycemic index, but sports drinks made solely from fructose usually result in plenty of gastrointestinal upset. Fructose is fine when it is not the only source of carbohydrate in a drink. Current science indicates that choosing a sports drink that provides several carbohydrate sources may work best, as this allows you to utilize a variety of transport mechanisms to bring the carbohydrates into your bloodstream. There still is a need to determine how these various carbohydrate sources affect blood glucose levels during exercise, how insulin levels are affected by the various types of carbohydrate, and of course how performance is affected. Keep in mind that in athletes without diabetes, insulin production does decrease during exercise, as contracting muscle produce their own insulin-like effect. This results in rapid uptake of glucose from the bloodstream. Ultimately, the choice of a sports drink may simply come down to your personal taste preferences and tolerances. Just keep in mind that your goal is to replace fluid losses as closely as possible, keep up with carbohydrate needs, and replace sodium losses. For athletes with diabetes, the optimum sports drink may be specific to that individual. Athletes who use insulin injections to control their blood glucose levels usually need to adjust their pre-exercise insulin and carbohydrate intake before, during, and after exercise in order to prevent hypoglycemia. In persons with Type I diabetes, a drink that prevents hypoglycemia and restores blood glucose is very important. Athletes with type II diabetes (who do not take insulin injections) likely would need to experiment to determine what drink and other nutrition strategies before training works best for them in combination with their medication regimen and diet. Glycemic index of various carbohydrates

Carbohydrate source Glycemic index Other considerations
Fructose   22-24 Not well tolerated as sole source of carbohydratein sports drink.
Galactose 22-24 No published data regarding this carbohydrate sourcein sports drinks.
Honey   55 Used in gel products.
Sucrose 65
Glucose 100
Maltodextrin 105 Source of “glucose polymers” which also have a highglycemic index. 


 

Sports Drinks (for 50 gm carbohydrate servings)
Gatorade 89 +/-27
XLR8 68 +/-15
Poweraid 65 +/-11
Cytomax 62 +/-15
Allsport 53 +/-9