Caffeine is a natural stimulant found in coffee beans, tea leaves, kola nuts and chocolate. It stimulates the brain and nervous system and helps to keep you awake, alert, focused and energetic. (Photo: mihailomilovanovic / Getty Images)

Billions of people worldwide depend on caffeine every day to wake up and get through the day.

A cup of coffee can be just the thing to help you get through that afternoon slump, or to help you survive the night shift.

Caffeine is a natural stimulant found in coffee beans, tea leaves, kola nuts and chocolate.

It stimulates the brain and nervous system and helps to keep you awake, alert, focused and energetic. It also functions as a diuretic.

There’s a synthetic form of caffeine that’s added to some cold medicines and pain relievers. Energy drinks contain man-made caffeine.

Once consumed, caffeine’s effects are felt fairly quickly. The amount contained in one 8-oz. cup of coffee enters the bloodstream within about 20 minutes, and its full effect is felt in about one hour.

Caffeine is kind of a double-edged sword. It confers a number of health advantages, but it can also be harmful in excess or under certain circumstances.

First, let’s take a look at the good things about caffeine — and there are actually quite a few of these.

Caffeine can improve brain function and mood. Studies show that when participants ingest caffeine they show improved short-term recall, reaction time and alertness.

Risk of depression is lower in those who consume caffeine.

The risk of developing Alzheimer’s and Parkinson’s is reduced among those who drink between three to five cups of coffee per day. And studies have consistently linked coffee consumption with a lower risk of Type 2 diabetes.

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Caffeine may also improve exercise performance. This means that if you consume caffeine before exercise, you can work out harder and longer before you feel exhausted.

And that translates into more calorie burning!

In fact, caffeine can increase metabolism and fat burning by 11-13%.

Caffeine is generally considered to be safe, but it is habit forming. Most people can consume up to 400 mg of caffeine a day without problems. If you go over that, you may experience side effects.

Common side effects include headaches, dizziness, rapid heartbeat, dehydration, anxiety, indigestion and insomnia.

Caffeine also interferes with the absorption of calcium in the body. It increases the release of stomach acid, sometimes leading to heartburn. It can temporarily increase blood pressure.

Caffeine lingers in the body for 8-12 hours before it is completely metabolized. So if you drink coffee in the afternoon, it is still going to be in your system when you go to bed. It will probably take you longer to go to sleep, you’ll wake up more often during the night, and you’ll get less restful sleep.

If you’ve been consuming caffeine on a regular basis, and suddenly stop, you’ll likely experience caffeine withdrawal. Headache and extreme fatigue are classic withdrawal symptoms. They usually last only a few days.

Susie Bond is a Registered and Licensed Dietitian/Nutritionist in private practice. Contact her at

Average amount of caffeine in 1 serving

Coffee, brewed, 8 oz., 100-200 mg

Espresso, 1 oz. (1 shot), 75 mg

Decaf coffee, 8 oz., 5 mg

Cola drinks, Mountain Dew, 12 oz., 50 mg

7-Up, Sprite, Ginger Ale, Root Beer, 12 oz., 0 mg

Energy drinks, 8 oz., 50-160 mg

Brewed tea, 8 oz., 50 mg

Chocolate milk, 8 oz., 5 mg

Hot chocolate, 8 oz., 5 mg

Chocolate bar, 1 oz., 5 mg

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