The caffeine content of coffee sold from high street outlets varies widely from store to store, with some containing as much as six times the quantity as others, according to new research. Researchers at Glasgow University studied 20 shops in the city and found that while Starbucks’ coffee contained 51mg of caffeine, four outlets sold the hot drink containing more than 200mg. An expresso from independent cafe Patisserie Francoise in the city’s West End contained 322mg. An expresso from Costa, meanwhile, contained 157mg of caffeine. Alan Crozier, from the research team at Glasgow University, said: “Despite the increasing number of coffee shops on the high street and in airports, there appear to be no recent publications on the caffeine contents of the various types of commercially prepared coffees. “This snap-shot of high street espresso coffees suggests the published assumption that a cup of strong coffee contains 50mg of caffeine may be misleading.” The study is published in the Royal Society of Chemistry’s journal Food and Function.