Scientists have published research showing caffeine not only boosts alertness but improves physical performance, reopening the debate about its use by athletes.

Researchers at the University of Birmingham in the U.K. found the stimulant increased the rate at which energy was taken up by the body by 26%.

This provided an energy boost that scientists believe would be of particular benefit in endurance sports such as cycling and long-distance running.

Caffeine, which constitutes a major ingredient in coffee and cola, was removed from the World Anti-Doping Agency (WADA) list of banned substances in January 2004, but controversy still surrounds its use.

Researchers at the School of Sport and Exercise Sciences in Birmingham tested the performance of road cyclists over three two-hour exercise sessions in which they drank different sports drinks, one containing glucose, one containing glucose and caffeine, and one plain water.

Dr. Asker Jeukendrup, director of the Human Performance Laboratory, said the drink laced with caffeine vastly outperformed the other two.

Jeukendrup said, "It is very difficult to regulate the intake of caffeine in an athlete's diet, as it is present in such a wide range of products like chocolate, nuts, flavorings and drugs, as well as coffee and cola.

"As long as caffeine remains off the banned list, I believe there is a case for a new generation of sports drinks that utilizes caffeine for its positive affects on delivering carbohydrates."

It is thought that use of the stimulant will be reviewed by the WADA at its annual meeting in September.