Caffeine: How Much is Too Much?

Whether it's coffee, tea, soft drinks, or energy drinks, most of us consume caffeine at some point in our day.

"It helps people stay alert and stay focused," says Lisa Casas, R.D., L.D., a clinical dietitian at University of Iowa Hospitals and Clinics. However, the effects of caffeine don't last for long. "It really doesn't stay in the system very long--it's only about two to three hours before it is excreted from the body," she says.

Caffeine is a naturally occurring substance. It is a common component in many leaves, seeds, and fruits. Foods and beverages derived from these plants contain caffeine. Common sources of caffeine include coffee, tea, and some soft drinks. Caffeine is also present in chocolate and in energy drinks like Monster Energy.

How to Safely Consume

Like most things, the key to caffeine is moderation. Most people should stick to around 300 milligrams (mg) of caffeine in a day.

Here are some of the most common foods and beverages containing caffeine along with their caffeine amounts.

  • an eight-ounce brewed coffee has anywhere from 60 to 120 mg of caffeine depending on how it is brewed
  • an eight-ounce serving of brewed tea has between 20 to 90 mg of caffeine
  • an eight-ounce serving of a caffeinated soft drink has 20 to 40 mg of caffeine
  • an ounce of milk chocolate has 6 mg of caffeine

Caffeine Myths

According to Casas, many of the myths associated with caffeine are untrue. For one thing, caffeine does not cause dehydration. "The amount of liquid consumed with caffeine will likely compensate for any diuretic effects associated with it," she says.

Because it may act as a mild stimulant to the central nervous system, some may classify caffeine as addictive. Not so, says Casas. "It's nowhere near comparable to a drug or tobacco addiction."

A sudden decrease in caffeine consumption may cause some individuals to experience mild symptoms of withdrawal such as drowsiness, fatigue, or headaches. However, Casas says, those symptoms will usually subside within a day or two.

Recent studies have also determined that moderate amounts (less than 300 mg) of caffeine are not harmful during pregnancy. If you are pregnant or if you have high blood pressure or heart disease, you may wish to consult your physician to determine the appropriate amount of caffeine that you should consume.