The exclusive use of gruit was gradually phased out in favor of the use of hops alone in a slow sweep across Europe occurring between the 11th century (in the south and east of the Holy Roman Empire) and the late 16th century (Great Britain) [REF].
Some authors present the switch to hops as a Protestant crackdown on feisty Catholic tradition, and as a Puritan move to keep people from enjoying themselves with aphrodisiac and stimulating gruit ales by imposing the sedative effects of hops instead.