Study Says Coffee Keeps Your Mental Health From Declining A UK study from 2016 says coffee protects the human brain against impairments and increases thinking skills. Dr. Donald Weaver, Krembil Brain Institute, via statement The key to brain-protecting benefits This makes them less complicated to produce. The study adds that a longer roasting time causes more phenylindanes to be created. This means dark roasted coffee has the strongest protective effect on the brain.