Caffeine is a naturally-occurring substance. It is a common component in many leaves, seeds and fruits. Common sources of caffeine include coffee, tea and some soft drinks. Caffeine is also present in chocolate and in energy drinks.
According to the National Coffee Association, more than 60 percent of American adults say they drink coffee every day, consuming just more than three cups. Drinking coffee is part of a daily routine for many people – researchers estimate that nearly 400 million cups of coffee are consumed each day in the United States.
As a general rule, you can assume that an average 8 ounce cup of coffee contains around 100 mg of caffeine. Several sources suggest that 400 mg of caffeine, or 4 cups of coffee, are safe for most healthy adults.
What are Caffeine Intake Limits?
In most cases, it’s not coffee that causes caffeine overdose but rather a combination of energy drinks, supplements and soft drinks — plus coffee or tea, too.
While it depends a lot on the person, a dose as little as 500 milligrams of caffeine and beyond could potentially produce some symptoms of caffeine overdose. Some people feel fine, or their perceived “normal,” drinking around 500 milligrams, while others feel sick and weak very quickly.
According to a recent study, people under the age of 55 who drink a lot of coffee – more than four cups per day – may be at greater risk of an early death.
"We're not saying that coffee is the cause of death; we just noticed coffee is associated with increased risk of death," Says Ochsner Cardiologist Dr. Carl Lavie. "The low doses seem to be very safe," Lavie said. "And that's still a fair amount of coffee."