"No question about it," says Dr. Barry Smith, a research psychologist at the University of Maryland.
"Up to five cups of coffee a day - or about 500 milligrams - and for some even more, is going to be perfectly fine," says Smith, a caffeine expert and director of the human-psychophysiology lab at the University of Maryland.
Like a pot of the black stuff on the tossing mess desk of a Navy warship, conventional wisdom has ebbed and flowed over the years on the merits of caffeine, Smith
"There have literally been thousands of studies done, and the drug has certainly had its ups and downs in terms of whether or not it's thought to be helpful," he
says, "but the current research over the past 10 years suggests that there are no obvious lasting dangers and that, in fact, there may actually be some benefits."
cautions that some people are more sensitive to caffeine than others.