And our national caffeine consumption may be higher than reported. Sales of "energy pills" are on the rise, yet a look at the ingredient list of many popular products often reveals guarana, mate, bissy nut, or cola nut, which are all simply herbal sources of caffeine. Ma huang and Chinese ephedra are herbal sources of ephedrine, another central nervous system stimulant.

The effects of caffeine in the body are linked to our "hardwired" biological stress-response mechanisms. Because life has always presented hazards, the human body is designed to react quickly and decisively to dangerous situations.

When triggered by "watch out!" signals such as loud noises, rapid movement, strong odors, and more, the body automatically produces both physical and chemical responses.

Surges of adrenaline heighten your mental awareness and sensitivity and prime your muscles for demanding movement such as jumping or running. Your pupils dilate, your breathing quickens, and eventually your natural cooling system kicks in and you start to sweat.

A single 250-milligram serving of caffeine (the equivalent of about 2.5 six-ounce cups of coffee) has been shown to increase levels of adrenaline by more than 200 percent. Caffeine also stimulates the production of norepinephrine, another stress chemical that acts directly on the brain and nervous system.

With daily use, caffeine can elevate levels of another stress chemical known as cortisol. Together, these bio-chemicals can increase heart rate and blood pressure and produce that "emergency" feeling. In a real-life emergency, all these survival mechanisms would help you get out of the way of a charging elephant or the 5:05 commuter train.

But what happens to the body when you are triggering a full-blown "fight or flight" response at regular intervals throughout the day, every day? The fact is that caffeine doesn't produce energy.

It stimulates your nervous system and adrenals, which is actually a form of stress on the body. Caffeine intake has been linked to increased blood pressure.

Research shows that people who consume more than 250 milligrams of caffeine per day (remember, that's what you'd get in 15 ounces of coffee) tend to have poor sleep quality. One study showed that 250 milligrams of caffeine decreased whole-brain cerebral blood flow by 30%. Other studies have found that caffeine reduces the oxygen level of brain tissue.

Research also shows that caffeine may be more damaging to women, producing adverse effects at lower intake levels. Women eliminate caffeine from their bodies more slowly than men, and this rate also changes significantly with the menstrual cycle. Other compounds,found in unfiltered coffee, have been linked to elevated cholesterol levels.

If you boil your coffee or drink espresso, which isn't filtered, you may want to limit how much you drink. Caffeine intake may also trigger a negative cycle of unhealthy behavior. Research shows that heavy coffee-drinkers also tend to smoke more, drink more alcohol, and eat more fatty foods than non coffee drinkers.

I like the taste of coffee just as much as anyone else, so it was hard to do, but when I finally cut down on my caffeine intake, I did see a very positive increase in my health, I lost weight, and found that, overall, I had increased and more constant energy levels.