Researchers claim, chocolate could provide the key to tackling a persistent cough. British researchers are carrying out the final stages of clinical trials on a drug that contains theobromine, an ingredient naturally present in cocoa and chocolate. If the trials are successful, the drug could be on the market within two years. Previous research by London’s National Heart and Lung Institute found that theobromine is 33 per cent more effective than codeine at stopping coughing. It works directly on the vagus nerve, which is responsible for persistent coughing. Research in South Korea has shown that theobromine has none of the side effects associated with standard drug treatments for persistent cough.