Maybe.

Maybe not.

A quick look at the label says it all:

• "Increases physical endurance and achieve a leaner body."
• "Rev up your metabolism and improve your reaction time."

And my personal favorite:

• "Revitalize your attitude and restore your faith in mankind."

These are the promises made by some of the new energy drinks (as opposed to sports drinks) crowding the shelves in grocery and health-food stores.

With names such as Energy, Power, Adrenaline Rush, and Whoop Ass, you might think these drinks would be the perfect choice for a pre-workout pick-me-up or a midday energy boost.

But no so fast. Here is the breakdown of what's in these drinks, what kind of performance boost they will provide (if any), and what their risks might be. But let me begin by saying this - there is no magic genies in these bottles.

Anatomy of an Energy Drink

Base: Energy drinks primarily consist of water and sugar, typically in the form of corn syrup, sucrose, or some other sweetener. The amount of sugar in these drinks is about the same as that in sodas and fruit drinks - about 25 to 40 grams per 8 ounce serving. That is equal to 5 to 8 teaspoons of sugar, or 100-160 calories per cup. That is more than twice the carbohydrate content of most sports drinks.

So this actually makes energy drinks a poor choice to drink prior to, or during a workout, because that much sugar hampers fluid absorption, giving you that sloshing feeling in your stomach. Many energy drinks also come in mega-sized bottles containing two or more servings, which makes it easy to gulp down loads of excess calories.

Stimulants: Many energy drinks owe their "buzz" to a wallop of caffeine - often more than 100 milligrams, which is more than twice the caffeine in a can of cola or equal to the caffeine in a cup of coffee. Guarana, an herbal source of caffeine, is also a popular additive. Both ingredients can increase your alertness and reaction time, but they can also boost your heart rate and blood pressure.

Since caffeine acts as a diuretic (i.e. it increases urine production), you risk dehydration if you take in excessive amounts. But because manufacturers aren't required to list the quantities of caffeine or guana in their drinks, judging your risk may be difficult.

Many energy-drinks fans claim taurine is what gives them a buzz. Taurine is an amino acid, one of the 20 that form the building blocks of protein. While taurine plays a vital role in certain bodily processes such as the digestion of fat, supplemental taurine has not proven beneficial. And no science shows that taurine can increase energy.

Vitamins and Minerals: Energy drinks typically include B vitamins such as thiamine, riboflavin, niacin, and vitamin B6. These play an major role in fat burning, and also release energy from carbohydrates during exercise.

What's more, some studies show that strenuous exercise programs, such as daily running, may slightly increase your need for these nutrients. But a healthful diet is still your best bet for meeting this increased need, because there is no evidence that a beverage loaded with B vitamins offers any special powers. And, in this case, more is not better; excess B vitamins are quickly excreted in your urine.

Some energy drinks claim to enhance the body's immune system with added zinc. Sure, we've all probably taken a zinc lozenge or two to try to knock out a cold. Zinc in this form is effective, but no evidence shows that consuming extra zinc in a drink can boost your immunity.

Chromium, a mineral that plays a key role in insulin function, is often added to energy drinks that claim to promote leanness. Yet numerous studies show that supplemental chromium does not aid in weight loss or muscle building.

Herbals: The list of herbal ingredients in many energy drinks reads like an alternative-medicine dispensary...from astragalus (said to increase energy and boost immunity) to yohimbe (thought to improve sexual function in men), these drinks contain a smattering of herbs in varying amounts. Still, these amounts are usually nowhere near what are thought to be therapeutic levels. Energy drinks that claim to boost performance, for example, typically contain ginseng. But they usually contain only about 100 milligrams of the herb, well below the amount needed to produce a feeling of well-being, according to research.

Energy drinks that claim to improve your mood and revitalize your mind often contain a trio of herbs-ginkgo biloba, kava kava, and St. John's wort. It is true that several studies show these herbs may positively affect mood or memory.

Ginkgo biloba, for example, has been shown to improve the memory of Alzheimer's patients, but not that of healthy adults. Likewise, kava kava has been shown to reduce symptoms of mild anxiety. But again, no energy drinks contain enough of these herbs to produce their purported effects. This is a good thing, in my opinion, because certain herbs can cause serious side effects. For instance, when ginkgo biloba is taken a therapeutic doses, it acts as a blood thinner. If you also take a daily dose of aspirin and vitamin E (which both thin your blood), you put yourself at risk for excessive bleeding from minor cuts or scrapes.

Body Shapers: Some energy drinks promise consumers leaner and stronger bodies by adding creatine, I-carnitine, hydroxycitrate, or pyruvate. Creatine has been shown to improve both sprint performance and muscle strength - and recovery. But here is a familiar catch: the amount added to energy drinks ranges from 25 to 250 milligrams, which is less than 1 percent of what you'd need to reap any performance enhancing benefits.

L-carnitine is a compound your body makes to burn fat, and hydroxycitrate is naturally produced by your body during the breakdown of carbohydrate and fat. Both have an obvious clinical connection to weight loss, yet studies show that neither increases your ability to lose weight when taken in supplement form.