The active ingredient in energy drinks varies, as do their side effects. None are superior, they all carry the potential to do awful things to your body.

CAFFEINE - It's good enough for coffee and tea, why not your energy drink? It works like amphetamines, cocaine, and heroin, in the way that it stimulates the brain. A typical 12 ounce can of a caffeinated energy drink contains 70-100 mg of caffeine, or the same as two sodas or a 6 ounce cup of coffee. Guarana, a common ingredient in energy drinks, contains caffeine.

Caffeine works by blocking the chemical that makes you naturally drowsy. The chemical, adenosine, is also responsible for dilating the blood vessels. By hiding adenosine, caffeine also causes the brain's blood vessels to constrict.

Your heart rate increases, muscles tighten, your blood pressure rises, blood vessels near the surface constrict and more blood flows to the muscles. Caffeine also increases dopamine in the brain. Dopamine is one of the chemicals responsible for feeling happy. Caffeine is a cardiac stimulant and mild diuretic.

While the short term benefits may seem positive, long term effects can be a real downer. Once the temporary stimulation wears off, your brain suddenly starts to recognize adenosine and a sudden mental sluggishness hits. Your heart racing is unhealthy unless it occurs naturally and is allowed rest periods. Sleep is affected because the internal effects of caffeine aren't over when the "high" is. It takes up to 12 hours for caffeine to completely vacate your body.

As a diuretic, caffeine speeds along your urination cycle, taking calcium with it. Long term, heavy caffeine use could lead to developing osteoporosis.

SUGAR - Most energy drinks, except those that are labeled "sugar free" and usually those marketed as "light" are high in sugar. The sugar in an 8 ounce can ranges from 5 to 8 teaspoons and usually accounts for 100% of the carbohydrates (80 - 130 calories). The RDA for sugar is no more than 6 - 7 teaspoons of sugar for each 2000 calories consumed. One bottle of energy drink contains all of the sugar you should eat in a day.

Sugar gives you a quick bump of energy because it is absorbed into the human body much faster than other energy sources, like protein. Studies show sugar can take effect within a minute of entering the body. Sugar raises the blood sugar level and gives you quick energy. This is often short lived, though, because the body quickly releases a blast of insulin, quickly lowering your blood sugar. When blood sugar plummets, so does energy and endurance.

While the short term side effects of sugar - crashing hours after consumption, increased appetite and the possibility of cavities - are somewhat mild, long term effects are not. Type 2 diabetes has been linked to sugar misuse. Weight gain due to the consumption of empty calories is becoming a bigger problem in the US and around the globe.

TAURINE, B VITAMINS AND GINSENG - These three ingredients are also commonly found in energy drinks.

Taurine helps move potassium, sodium, calcium and magnesium into and out of cells and generates nerve signals.

B Vitamins are important for many functions of the body including reduction of stress and depression, metabolism and digestive system. However, too much vitamin B can cause nausea, gout, hypothyroidism, insomnia or reduced insulin release, among other side effects.