Chances are, you have some caffeine in your system right now; you might even be reading this article with a cup of coffee, a can of soda or a mug of tea in hand. But how much do you know about the drug — and yes, it is a drug — you're consuming? Before downing one more gulp of your favorite stimulant, let go of some persistent, caffeinated myths.

1. Americans now consume more caffeine than ever.

With a Starbucks or Dunkin' Donuts on every corner; grocery coolers full of soft drinks, energy drinks and teas; and convenience-store counters displaying 5-hour Energy shots, it seems that we are more caffeinated than ever.

Except we aren't. U.S. coffee consumption peaked 65 years ago, then fell dramatically. From 1946 to 2005, it declined roughly by half, from 46 gallons per person each year to 24 gallons. And despite the abundance of new ways to consume caffeine, we still get most of our caffeine from coffee. Two recent surveys, one by the Food and Drug Administration and one for an industry-backed research group, show that coffee accounts for two-thirds of the caffeine in the American diet.

As coffee drinking fell, soft drink consumption surged, rising from 11 gallons per person annually in 1947 to 51 gallons in 2005. But, with their lower caffeine content, soft drinks have not replaced the caffeine we've dropped from our diets by drinking less coffee.


That's something to bear in mind the next time you hear phrases like "In our hyper-caffeinated society ... ."

2. Energy drinks have more caffeine than coffee.

Not really. Let's start with the classic Red Bull. The original 8.4-ounce can has 80 milligrams of caffeine. That's equivalent to a mere four ounces of drip-brewed coffee from Starbucks.

Cans of the super-size energy drinks such as Monster and Rockstar are twice the size of the little Red Bulls, with roughly twice the caffeine. At this serving size, the drinks begin to approach the caffeine levels of coffee. One analysis found an average of 188 milligrams of caffeine per 16-ounce cup of coffee. A can of Monster contains 184 milligrams.

But even these larger energy drinks don't approach the caffeine levels of Starbucks coffee, which tends to have higher caffeine concentrations than Dunkin' Donuts coffee, for example. Starbucks claims approximately 260 milligrams of caffeine per 12-ounce cup of drip-brewed coffee ("tall") and 330 milligrams per 16-ounce cup ("grande"). Few energy drinks approach the latter level, which equals four Red Bulls. A 22-ounce bottle of NOS, an energy drink bottled by Coca-Cola, does contain 220 milligrams of caffeine. That is a lot, but an equal-size serving of Starbucks coffee would have twice as much.

Bottom line: If you want a strong caffeine jolt, stick to the joe.

3. Most pure caffeine is derived from plants like coffee and tea.

For more than 100 years, bottlers have been blending the pure, powdered form of the drug into soft drinks. (When the practice began, Coke and Pepsi were marketed as tonics for fatigue, and caffeine gave them their pep.) The United States now imports more than 15 million pounds of powdered caffeine annually; most for use in soft drinks. In the early days, it was produced by domestic chemical companies such as Monsanto, which began extracting caffeine from waste tea leaves in 1905 to supply Coca-Cola. Some caffeine is still produced this way, and some as a byproduct of coffee decaffeination.

But most of the powdered caffeine we now use is synthesized in pharmaceutical plants, primarily in China but also in Germany and India. The caffeine is not extracted from natural plant products such as coffee or tea, but assembled from chemical precursors including urea and chloroacetic acid.

Whatever the origin, the chemical is the same, and it has the same physiological effects. But the forms are distinguishable by laboratory analysis.

4. Caffeine is a diuretic.

Anyone who has slammed a large cup of coffee and then been stuck in a traffic jam may conclude that caffeine is a diuretic. But University of Connecticut researchers studied the effects of caffeine on healthy, active men in 2005 and found no indication of such an effect. Their study, which followed subjects for 11 days of controlled caffeine consumption, came to this conclusion: "These findings question the widely accepted notion that caffeine consumption acts chronically as a diuretic."

Because caffeine has been considered a diuretic, people have worried that drinking coffee can contribute to dehydration. In a study published this year, however, researchers in England looked specifically at caffeinated coffee. Their subjects were 50 men who consumed similar amounts of coffee or water while researchers measured their urine output. The result? No dehydration.

The authors say it's time to bust the dehydration myth: "These data suggest that coffee, when consumed in moderation by caffeine habituated males contributes to daily fluid requirement and does not pose a detrimental effect to fluid balance. The advice provided in the public health domain regarding coffee intake and hydration status should therefore be updated to reflect these findings."

It may be little comfort to that bursting bladder, but caffeine isn't to blame.

5. Gourmet coffee is typically dark-roasted.

When the specialty-coffee movement took off 20 years ago, it was led by Peet's and Starbucks. By serving coffee that was roasted dark and brewed strong, both distinguished themselves from the lightly roasted and often weakly brewed commercial coffee Americans were used to. As Starbucks took the nation by siege, many people came to associate coffeehouses with dark-roast coffee. (Along the way, the chain acquired the moniker Charbucks, from those who thought its coffee was roasted to ashes.)

But then the pendulum started to swing back. In 2008, Starbucks introduced Pike Place Roast, a medium-roast coffee that's served alongside the dark "bold pick of the day." Meanwhile, a slew of upstart coffee companies emerged. Roasters such as Blue Bottle, Intelligentsia and Stumptown, serving self-proclaimed coffee snobs, carved out their niche by roasting coffee very lightly. Following their lead, Starbucks introduced its Blonde Roast coffee in 2011.

Connoisseurs argue that lightly roasted coffee preserves more of the bean's distinct flavors. Maybe, but to unsophisticated palates like mine, it often tends to taste sour. I go for medium-roast coffee, the most pedestrian of roasting strategies. (The darkest-roasted beans have slightly less caffeine, bean for bean, than the lightest; some caffeine is lost in the roasting process.)

Of course, if you prefer dark-roast coffee, fret not. In a decade or so, the pendulum is bound to swing the other way again.

Murray Carpenter is the author of "Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us."