Student or Learner
Many of us have heard the statistic that heart disease is the leading causes of death in the U.S. The good news for those at risk everywhere is that caffeine has been shown to reduce this threat significantly.
First of all, is it all right to replace "the leading cause of death" with "the major causes of death?"
Second, why is it the passive voice--caffeine has been shown? Would the active voice do the same trick--caffeine has shown? Thanks.