Caffeine is a natural substance that can be extracted from plants. Natural sources of caffeine include coffee beans, tea leaves and cocoa beans. It also can be produced synthetically.

Caffeine is a type of drug that promotes alertness. These drugs are called “stimulants.” Caffeine acts as an “adenosine receptor antagonist.” Adenosine is a substance in your body that promotes sleepiness. Caffeine blocks the adenosine receptor to keep you from feeling sleepy.

Caffeine begins to affect your body very quickly. It reaches a peak level in your blood within 30 to 60 minutes. It has a half-life of 3 to 5 hours. The half-life is the time it takes for your body to eliminate half of the drug. The remaining caffeine can stay in your body for a long time.

Coffee accounts for 54% of the caffeine consumption in the world. Tea accounts for another 43%. On any given day, about 85% of Americans use caffeine products. The average daily consumption of caffeine by adults in the U.S. is about 300 mg per person. This is about three times higher than the world average. But it is still only half of the caffeine consumption in heavy tea-drinking countries such as England and Sweden.

Caffeine is a product that has both positive and negative effects. These effects depend on the amount of caffeine you consume and when you consume it:

Positive Effects of Caffeine

Caffeine is considered a moderately effective alerting agent. It can have a positive effect on your reaction times, mood and mental performance. A normal dose of caffeine is about 50 mg to 200 mg.

Caffeine works best when you take it on an intermittent, off-and-on basis. Higher doses can have much more potent effects. A dose of 500 mg or 600 mg of caffeine can affect you much like a low dose of an amphetamine. When you consume caffeine daily, it is less effective as a stimulant. Your body builds up a tolerance to it.

Negative Effects of Caffeine

Caffeine can have a disruptive effect on your sleep. The most obvious effect of the stimulant is that it can make it hard for you to fall asleep. One study also found that caffeine can delay the timing of your body clock. These effects will reduce your total sleep time. Caffeine also can reduce the amount of deep sleep that you enjoy.

The effects of caffeine can occur even when you consume it earlier in the afternoon or evening. One study found that consuming caffeine 6 hours before bedtime reduced total sleep time by 1 hour. These effects also can be stronger in older adults. It takes their bodies a longer time to process caffeine. Regularly consuming high doses of caffeine may cause complications during pregnancy.

At high doses, caffeine can produce these common side effects:

  • Diarrhea
  • Sweating
  • Nausea
  • Increased heart rate
  • Increased breathing rate
  • Muscle tremors

Withdrawal symptoms can occur when you stop taking caffeine after using it regularly for a long time. These symptoms include:

  • Headaches
  • Sleepiness
  • Low energy levels
  • Bad moods

The FDA is collecting reports of adverse events that have occurred in people wh