Along with helping to pry open the eyes, coffee could lower the risk of gallstones and Parkinson's disease, said Dr. Neal Benowitz, an internist and researcher at UCSF.
A second or even third cup is OK, he said. But coffee's stimulating effects don't pack the same jolt after that, Benowitz's research concluded, and could build tolerance for caffeine that can lead to other problems.
"The effect of each dose is less and less," Benowitz said Tuesday. "You're better not to drink it regularly, then have a big cup, and it'll pep you right up."
Benowitz accumulated his findings over the years, along with those from other studies, in researching concerns of the coffee craze. He pointed to other studies that have found that some coffee intake might reduce the risk of Parkinson's diseasefor reasons still puzzlingand could lower the risk of gallstones.
But, he cautions, a double shot with a twist isn't for everyone.
Pregnant women and those with migraines, heartburn, high blood pressure or anxiety should steer clear of the buzz that comes from coffee.
And those already taking caffeine in supplements should leave the coffee in the pot.
"Is it a major health concern? I conclude it's not a major health concern," said Benowitz. "There may be some specific people who should avoid it, but for most people it's not a problem."
Try telling that to Deidre Larkin, a lecturer in food and science nutrition at California State University, Northridge, who won't touch the stuff.
"I chose not to use anything that might have any control over me, and caffeine is physiologically addicting," she said, pointing out that colas, some over-the-counter medicines and other products routinely contain doses of caffeine.
"It's a stimulant. ... There may be some benefits, but for me the day-to-day disadvantages outweigh the benefits," she said.
But what about bleary-eyed sleepyheads who can't walk out the door without their morning cup of joe? "Tell them to get up and go to the gym," she said.
Still, more than 100 million American adults belly up to the coffee bar each day for their coffee, and a spokesman for the National Coffee Association says public health officials find no problem with that.
After thousands of studies coffee still flows freely in the United States because it's considered safe, industry spokesman Gary Goldstein said.
"Public health authorities don't regulate caffeine because they consider it safe," said Goldstein.
But, if caffeine intake has coffee drinkers on edge, experts say certain types of beans and methods of brewing can cut the milligrams per serving.
Dark-roasted beans might contain more caffeine than light-roasted varieties, and robusta beans generally have more caffeine than arabica, Goldstein said.
The numbers tell it straight: Caffeine in a basic eight-ounce cup of coffee can range from 65 to 120 milligrams.
Instant coffee packs a smaller punch, with 60 to 85 milligrams, while a single shot of espresso weighs in at 30 to 50 milligrams.
Still, despite the ease at which the nation tips its mug, coffee isn't for everyone.
Pregnant women, for example, should limit their coffee intake because caffeine has been associated with lower birth weights of babies, experts said.
Plus, even at just one or two cups a day, coffee drinkers do develop dependence, which can lead to problems once the java stops flowing, Benowitz said.
"You can feel flulike symptoms. They are not life-threatening, but they can be very uncomfortable," he said. "That can be a problem. They feel really lethargic in the morning. They have to have coffee to get going."
"It goes back to the idea of moderation in all things," said Carol Koprowski, a CSUN assistant professor of family environmental sciences who specializes in diet and breast cancer. "What you know today may not hold true tomorrow."
Koprowski doesn't drink coffee, but has grown to love coffee houses and the social interaction they provideeven as she orders up hot chocolate instead of a double cappuccino.
"It's a very relaxing time. There's a lot to be said for it," she said. "I'd certainly rather have my friends out having a cappuccino or a latte, rather than at a bar having too much to drink."