The use of dietary supplements has increased in the United States in recent decades . Folic acid , vitamin C , magnesium , zinc and copper pose an increased risk . Iron was most strongly linked to an increased risk of earlier death -- calcium was the least . Increases in mortality risk were extremely small and may not be clinically meaningful .
The use of dietary supplements has exploded in the United States in recent decades . Folic acid , vitamin B6 , magnesium , zinc and copper pose an increased risk . Iron was most strongly linked to an increased risk of earlier death -- calcium was the least . Increases in death risk were extremely small and may not be clinically meaningful .