Starbucks to Costa Coffee: Which has the strongest caffeine hit?

Caffeine is a stimulant found in coffee, tea, cocoa and more than 60 other products - and consumed by millions of people around the world daily [File: Waldo Swiegers/Bloomberg]

Unbeknown to coffee lovers, there is a “big” difference” in caffeine levels between high-street shops such as Starbucks and Costa Coffee, a UK-based study has found.

While a single shot of espresso at the Caffe Nero chain would provide a coffee enthusiast with 45mg of caffeine, the same-sized drink at Pret contained 180mg, the consumer rights and research group Which? reported on Wednesday.