Maybe it's the sleepless nights. Maybe it's the daytime jitters. Whatever the reason, many people decide to cut back on caffeine - only to find that it's harder than they thought.
Caffeine turns up in expected places, in unexpected amounts. And recent years have seen an explosion in the number of caffeinated products on the market: energy drinks, of course, but also chewing gum, candy bars and (for a brief while) potato chips. A lack of labeling guidelines leaves many consumers in the dark about just how much caffeine the products contain.
There are a variety of reasons why such labeling would help consumers, says James Lane, a professor of medical psychiatry at Duke University Medical Center in Durham, N.C., who has studied caffeine's effects on the body.
Excess caffeine can exaggerate attention deficit disorder, hyperactivity and insomnia, Lane says. It can increase blood pressure, heart rate and secretion of stress hormones. It may also hamper the body's ability to regulate blood sugar levels.
Research suggests caffeine can harm developing fetuses too: Several studies have linked the consumption of more than 200 to 300 milligrams of caffeine daily during pregnancy to an increased risk of miscarriage and low birth weight. As a result, the Food and Drug Administration advises pregnant women to limit how much they consume.
But "without caffeine content on packaging, it's impossible to follow this advice," says Bruce Silverglade, legal director for the Washington, D.C.-based Center for Science in the Public Interest, a nonprofit group that has advocated for national caffeine labeling standards for more than a decade. "It turns up in unexpected places. There's no way to keep count."
Caffeine that's present naturally, from a food ingredient, doesn't require labeling, but if caffeine is added to a food or drink, it must appear on the list of ingredients, says Siobhan DeLancey, a public affairs specialist at the FDA. But the agency does not require manufacturers to disclose how much caffeine is in the product.
Coke, Pepsi labels
In recent years, some manufacturers have begun to voluntarily provide that information. In 2007, Coca-Cola and Pepsi began listing caffeine content on beverage labels, citing a desire to give consumers more information. Consumers can now see for themselves that an 8-ounce serving of Coca-Cola contains 23 milligrams of caffeine and that the same amount of regular Pepsi contains 25.
That's about average for most cola products, according to the U.S. Department of Agriculture's National Nutrient Database. But the precise amount of caffeine in other sodas varies greatly.
A 2007 study published in the Journal of Food Science revealed that the caffeine contents of more than 130 brands of soda nationwide ranged from roughly 5 to 75 milligrams per serving, says study author Leonard Bell, professor of nutrition and food science at Auburn University in Auburn, Ala.
Of course, most people who pick up a can of soda, or a so-called energy drink, do so expecting a little pick-me-up. In fact, some energy drink makers voluntarily declare their caffeine content as a selling point aimed at those consumers looking for a boost.
But when caffeine crops up in other products - yogurt, ice cream or jelly beans, for instance - consumers could really use some added information, Silverglade says.
These sources are significant, given that snacking on coffee-flavored yogurt or a chocolate bar can provide a bigger dose of caffeine than a serving of Coke or Pepsi.
A serving of Hershey's Special Dark chocolate bar, for example, provides 31 milligrams of caffeine, and a serving of Ben & Jerry's coffee-flavored ice cream provides 68 milligrams, according to the Center for Science in the Public Interest.
Labeling all caffeine-containing products with the precise caffeine content does pose significant challenges, Bell says, because the amount found naturally in products such as tea, coffee, chocolate and coffee-flavored ice cream or yogurt differs depending on the variety and crop growing conditions.
"It's just like an orange from Florida and one from California -- they're not going to have the same vitamin C content," Bell said.
Nor, for that matter, will two cups of coffee from the same bean contain the same caffeine -- it will depend on how you brew your coffee or how long you let it steep.
But Bell and many food scientists and nutrition advocates agree that when caffeine is added to a food or drink as an independent ingredient, consumers would benefit from having the precise amount listed on the label. Others, such as Silverglade, argue that standardized labels are needed on all caffeine-containing foods -- precisely because unexpected foods can contain significant amounts of the stimulant.
The information would be helpful not only for people concerned about caffeine's potentially harmful effects but also for those who are particularly sensitive to its stimulating properties, as well as parents trying to control their children's caffeine intake.
"If it's on the label, people can have data at the point of purchase," Bell says. "They don't have to go to the computer and say, 'OK, let me see if I can find it.' "
To make any changes to current rules, the FDA would have to draft a proposed rule and then solicit public comment, said the agency's DeLancey. Any plans to do so? "We generally wouldn't make that public until putting out the draft for comment."