It's said to be the most widely consumed mood-altering substance in the world, and chances are good that you had a dose or two this morning. And maybe you'll have more with an iced tea at lunch and when you hit the vending machines for a soft drink or a candy bar.
Caffeine has become a ubiquitous component of food and drink, naturally present in many and added to others in man-made form.
So might you be getting too much caffeine?
That's possible, especially if you feel jittery or have trouble falling asleep. But if you don't overdo it, the experts say, caffeine appears to be fine for most healthy people.
"When consumed in moderation, caffeine has no adverse health effects," said Dr. Luis Gruberg, a professor of medicine at Stony Brook University School of Medicine's cardiovascular diseases division.
In fact, caffeine may even help keep the brain in good working order.
Still, caffeine is not for everyone, especially those with certain medical problems and those who can't handle its effects. But it can be hard to avoid.
WHERE CAFFEINE LURKS
A bitter white powder, caffeine is found in a variety of plants that make their way into food and drink. Gruberg said that an 8-ounce cup of brewed coffee typically contains about 135 milligrams of caffeine, while brewed tea contains about half that. Caffeine in soft drinks ranges from 22 to 71 milligrams, and energy drinks can have as much as 300 milligrams, he said.
But caffeine lurks in other places, too -- like coffee-flavored ice cream and frozen yogurt (as much as 84 milligrams in an 8-ounce serving), in two tablets of Excedrin (130 milligrams) and in a Hershey's Special Dark Chocolate Bar (33 milligrams), among others, according to the Center for Science in the Public Interest.
Knowing the caffeine content of foods and drinks can be critical for people who have trouble sleeping, especially if caffeine is being consumed in the afternoon or evening, explained Dr. Alex Vidal, a heart rhythm specialist at Nassau University Medical Center in East Meadow.
Who should limit intake
Vidal said that people with heart disease should limit coffee intake to one cup a day and avoid caffeinated soft drinks altogether because they may contain too much caffeine. Those with uncontrolled blood pressure should avoid caffeine entirely because it can boost their blood pressure, he said.
Stephanie Giraulo, a registered dietitian and director of nutritional services at St. Charles Hospital in Port Jefferson, said that people with stress and anxiety disorders also should be careful about caffeine, as should pregnant women and anyone with acid reflux disease or stomach ulcers.
Children usually don't need to avoid caffeine entirely, although that might be a good idea for a hyperactive child, Giraulo said. But soft drinks that contain caffeine can be a problem for children in another way, she said, because they may replace healthier, less sugary drinks, like milk.
But caffeine does have benefits, reiterated heart specialist Vidal, who said he drinks a couple of cups of espresso daily. "We know that caffeine definitely leads to an increase in mental alertness," he said, "and some studies have also proven that it leads to improvement in mental function such as reasoning and memory."
Vidal also noted that coffee, tea and chocolate -- which can all have caffeine -- have been shown to be healthful in some ways, but that stems from the antioxidants they contain rather than the caffeine.