An ingredient in chocolate could be used to stop persistent coughs and lead to more effective medicines, researchers said on Monday.

The study found that theobromine, found in cocoa, was nearly a third more effective in stopping persistent coughs than codeine, currently considered the best cough medicine.

The researchers, from Imperial College London (ICL), said the discovery could lead to more effective cough treatments.

“While persistent coughing is not necessarily harmful it can have a major impact on quality of life, and this discovery could be a huge step forward in treating this problem,” said Professor Peter Barnes of ICL and Royal Brompton Hospital.

Ten healthy volunteers were either given theobromine, codeine or a dummy pill during the trial, which also involved Royal Brompton Hospital and St Bartholomew’s Hospital.

To measure the effect of the different pill, the researchers measured the response to capsaicin, which is used in research to cause coughing and as an indicator for the effectiveness of medicines.

The team found when the volunteers were given theobromine, the concentration of capsaicin needed to produce a cough was around a third higher than in the placebo group.

When they were given codeine they needed only marginally higher levels of capsaicin to cause a cough compared with the placebo.

The researchers, writing in the online FASEB Journal, said that theobromine worked by suppressing vagus nerve activity, which is responsible for causing coughing.

They also found that unlike standard cough treatments, theobromine caused no adverse effects on the cardiovascular or central nervous systems, such as drowsiness.

SOURCE: The FASEB Journal, November 17, 2004.