By Alan Mozes

NEW YORK, Mar 28 (Reuters Health) -- Athletes interested in getting an energy boost may want to choose their "energy bars" carefully, a report suggests. Some products may cause a spike in blood sugar that is similar to that seen with a candy bar, while others may provide a lower energy boost that does not peter out over time, according to an Ohio researcher.

While such bars enjoy "enormous popularity" -- the three top-selling bars made $160 million in sales in 1997 -- they have not been well-studied, noted Dr. Steve Hertzler, who is currently at Ohio State University in Columbus.

"The manufacturers of the bars are making claims that their bars have such and such complex carbohydrates and you won't have to worry about spikes in blood glucose levels that would happen with candy bars," Hertzler told Reuters Health. "My concern about these energy bars was that they were very poorly studied."

In a new study, Hertzler looked at the boost in blood sugar seen in 12 healthy volunteer subjects -- 10 women and 2 men -- after they consumed one of two types of energy bars, a candy bar, or four slices of white bread.

Each test meal contained 50 grams of carbohydrates. One meal included a moderate-carbohydrate energy bar called the "Ironman PR Bar"; and a high-carbohydrate energy bar known as the "PowerBar." The carbohydrates in the bars are derived from high-fructose corn syrup, and some brands contain pear juice concentrate and brown rice.

The peak blood sugar level was achieved with both the Ironman PR Bars and the PowerBars 30 minutes after consumption. However, the Ironman PR Bar had a lower peak than the PowerBar, the bread, and the candy bar. In addition, the Ironman PR Bar continued to result in blood sugar levels lower than the other three meals 45 minutes after consumption, which was the time point at which the bread and candy bar elicited their highest blood sugar level. An hour after eating the meals, there were no differences in blood sugar.

Hertzler concludes that the Ironman PR Bar -- which gets 40% of its energy from carbohydrates -- was the only one that caused blood sugar to remain steady at an elevated rate, while the PowerBar -- which contains more than 70% carbohydrates -- caused a steep increase and rapid decline in blood sugar.

The results suggest that sports participants should choose their energy bars based on their particular activity, said Hertzler, who conducted the study while at Kent State University in Ohio.

"You have to know what kind of sport you're in," he noted. "In a short term 5-K run, you're not going to be too concerned about the glycemic index (blood sugar level) because you will be done in about 30 minutes or so, before the 'crash'. But if you're in a long-term event then I would shoot for a lower glycemic index food."

However, the findings may not necessarily apply to athletes, because the study was conducted mainly in sedentary individuals, according to Jones Chan, the director of research and development at Powerfood in Berkeley, California -- the manufacturer of PowerBar.

"PowerBar is designed for consumption before, during, and after athletic events. Blood glucose responses and fueling needs under these conditions are very different than in sedentary conditions," Chan stated. "As such, a generalization of the results of this study to athletes/athletic situations should not be made."

The company also recommends that 8 to 16 fluid ounces of water be consumed with the bar, while study subjects were allowed to consume up to 8 ounces of water.

The bar contains "grain fibers which form a gel when combined with water. This gelling around the matrix causes a slow release of macronutrients such as carbohydrates. Water consumption may not be enough in this study to activate the gelling mechanism," Chan explained.

SOURCE: Journal of the American Dietetic Association 2000;100:97-100.

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