“The analysis that we did showed the amount of caffeine ranged from 50mg per cup from Starbucks, up to over 300mg per cup from another coffee house, Patisserie Francoise,” a Scottish researcher said. “I was very surprised by this.”http://www.bbc.co.uk/news/uk-scotland-glasgow-west-15968515
This is less than the caffeine in one mug of tea, calculated at 75mg. http://www.bbc.co.uk/news/health-15982904
