The Highs and Lows of Caffeine

At least four out of five Americans regularly consume caffeine, the most widely used behaviorally active drug in the world. But does caffeine cause more than just a morning boost?

Over the years, caffeine has been singled out as a possible factor in ]]>heart disease]]> , cancer, and birth defects, among others. Here's a look at why most experts say that moderate caffeine consumption is not a habit worth losing sleep over, and some advice for "addicts" who want to cut back.

What's New?

Energy drinks are the latest entry into the beverage market and perhaps the most potent way to get a caffeine fix. The popularity of these carbonated, hybrid, coffee-flavored cola drinks has skyrocketed since they first appeared on the market in 1997. They are particularly popular among the younger generation, including teenagers. Does the entry of another caffeine-containing concoction into the marketplace prove yet again that we're a nation of addicts?

Can You Be Addicted to Caffeine?

In a manner of speaking, yes. Some 80% of Americans regularly consume caffeine, a drug that acts as a central nervous system stimulant. It increases heart rate, boosts urine production, and raises the metabolic rate (the speed at which the body burns calories to fuel necessary functions such as breathing). And as anyone who can't get going in the morning without a cup of coffee, tea, or a caffeine-containing soft drink knows all too well, caffeine can be habit-forming.

While most experts say "addiction" is too strong a word to be used in conjunction with caffeine, researchers at Johns Hopkins University have identified a condition they call "caffeine dependence syndrome," characterized by at least three of the following four criteria:

• Withdrawal symptoms, such as headache, fatigue, and depression
• Caffeine consumption despite causing physical problems, such as irritating an ulcer
• Unsuccessful attempts to cut back on caffeine
• Tolerance to caffeine (for example, the ability to drink an extra cup of coffee and still fall asleep

Is It a Habit Worth Breaking?

Although the idea of being "dependent" on caffeine is unsettling, most healthy people who drink a cup or two of coffee, tea, or soda every day suffer no more serious physical symptoms than jitteriness, irritability, and minor gastrointestinal upsets. Why, then, have scientists long suspected that caffeine might contribute to heart disease, cancer, birth defects, and other problems?

The snag here is that much of the early research linking caffeine to various conditions was clouded by a number of issues. When questioning people about their caffeine-consuming habits, for example, many researchers failed to ask about caffeine sources other than coffee or tea, such as soft drinks, chocolate, and certain medications (see chart).

In addition, most early studies neglected to account for differences in methods of preparing coffee. For example, some research has suggested that coffee drinking raises blood cholesterol levels. Yet most of that evidence comes from Scandinavia, where coffee is boiled rather than brewed.

Studies in the United States, on the other hand, have not come up with the same coffee-heart disease connection, presumably because coffee is brewed, which passes coffee through a filter. This process probably filters out certain chemical substances, which may be the cholesterol-raising culprits.

Another confounding issue is that even though caffeine and coffee drinking may not contribute to disease in and of themselves, they seem to go hand-in-hand with a lifestyle that does. One study conducted by researchers at the University of California, San Diego, found that coffee drinkers were more likely to smoke, drink alcohol, and eat high-fat diets than abstainers.So maybe it’s not the coffee, but rather the cream or cigarette accompanying the coffee that contributes to health problems.

Another report from a group of Boston-based researchers showed that compared to women who drank regular coffee, women who chose decaf were more likely to exercise and eat vegetables regularly.

Who Should Keep Caffeine in Check?

Some people would clearly do well to limit their caffeine consumption, or avoid it altogether. For example, people with ulcers or ]]>heartburn]]> should stay away from caffeine because it stimulates the secretion of acid, which can irritate the lining of the gastrointestinal tract. (The chemicals in decaf coffee also boost acid secretion.)

Pregnant women should watch the amount of caffeine they consume, as well. While moderate amounts (a cup or two of coffee a day) have not been proven to cause birth defects, caffeine does cross the placenta. Once caffeine enters the fetal bloodstream, large amounts can alter the unborn baby's normal heart rate and breathing. Some research also suggests that large amounts of caffeine may decrease bloodflow to the placenta, which in turn may raise the risk of miscarriage.

People with chronic headaches are strongly advised to quit all caffeinated products. Many headache specialists link caffeine intake with tension headaches.

On the other hand, there is some preliminary data that suggest caffeine intake my lower the risk of diabetes. Coffee may work by improving body’s sensitivity to insulin.

Are You Contemplating Quitting?

Even if you only drink a cup or two of coffee, tea, or soda each day, try to cut back on caffeine gradually. Moderate caffeine users who stop cold turkey often suffer from withdrawal symptoms such as headaches, fatigue, moodiness, and nausea. Instead of switching over completely to decaffeinated coffee, substitute decaf for half your regular blend for a couple days and gradually wean yourself. Or, alternate decaf sodas with the regular version throughout the day until you feel comfortable weaning yourself from the caffeinated version completely.