The Good And The Bad About The Ubiquitous Stimulant (Caffeine)

A triple nonfat mocha may taste good, but it's likely the jolt that drives millions of people to fork over three bucks or more for the steaming cup of brown liquid.

Between 80 percent and 90 percent of North Americans consume caffeine regularly, according to a 2004 review, with an average daily consumption equivalent to about two mugs of coffee or four 16-ounce bottles of soda.

The habit has become less guilt-inducing recently, with growing evidence that both coffee and tea can fight cancer, heart disease, diabetes, Parkinson's disease and more. Because most people equate these beverages with the caffeine in them, it's tempting to conclude that the stimulant is what gives these wonder drinks their powers. That may not be the case.
Caffeine's effects on health appear to be considerably more nuanced.On the plus side, the drug does appear to help protect the brain from degenerative disease, give triathletes a nose over the finish line and, for many, keep the brain's gears churning, which is what drives most people to drink it in the first place. But habitual and large doses of caffeine can also stress the heart and interfere with insulin's ability to process sugar.

And many of the benefits ascribed to caffeine may be due, in fact, to other chemicals that outweigh caffeine's negative effects.

"As soon as you say coffee, people think caffeine; as soon as you say caffeine, people think coffee," says Terry Graham, a metabolic physiologist at the University of Guelph in Canada, a longtime caffeine researcher who recently organized an international symposium on caffeine and health.

Scientists have isolated antioxidants, polyphenols, and micronutrients from coffee and tea, but there have been no long-term studies of how each ingredient, including caffeine, affects the body on its own or within a beverage.

"There are health benefits of coffee that have nothing to do with caffeine," Graham says. In fact, he adds: "There are no health benefits I've ever seen documented for caffeine."

Anyone who has used a latte to get through an after-lunch meeting - or ended up with stomach-churning jitters after one too many shots of espresso - knows that ingesting caffeine has physical consequences. The molecule, which is identical in every beverage that contains it, blocks the action of a naturally produced chemical called adenosine.

Produced in the brain, adenosine normally accumulates during activity and declines during sleep. By the end of the day, it dulls the nervous system, causing drowsiness and a sense of calm and helping the body fall asleep. When caffeine gets in its way, by binding to adenosine receptors throughout the body, a rush of energy creates a feeling of alertness.

In dozens of studies, says Peter Rogers, lead researcher of the Dietary Caffeine and Health Study at the University of Bristol in Britain, caffeinated people have faster response times than noncaffeinated people. And a 2005 brain-imaging study showed caffeine lighting up the brain's short-term memory center.

The studies may simply prove how addictive the drug is, Rogers says. These experiments usually involve regular caffeine-drinkers who abstain for a day or two before the study.

"What we find is that if you take caffeine away from caffeine drinkers, they perform worse ... than people who don't normally get caffeine," Rogers says.

When people normally caffeine-free get caffeine, however, studies show a small to negligible mental boost, says Rogers.

It may be withdrawal that makes people falter, he says, not caffeine that makes them sharper.

A number of long-term studies comparing the overall health of heavy coffee drinkers with abstainers have turned up perplexing results, at odds with the findings of controlled experiments.

Some data, for example, suggest that drinking coffee might help prevent heart disease. Coffee contains thousands of compounds that might be responsible for such benefits, but polyphenols, similar to the healthful compounds found in chocolate and red wine, as well as antioxidants are the most likely candidates.

Several large studies have linked large daily doses of coffee with lower rates of Parkinson's disease, as well. And coffee drinking has also been linked to lower rates of liver cancer, Type 2 diabetes and gout, among other ills.

Scientists warn that the benefits probably come from ingredients other than caffeine.

Pure caffeine, in fact, can exacerbate the symptoms of diabetes. Graham and colleagues have done studies that showed caffeine makes insulin less efficient at removing sugar from the bloodstream.

In serious athletes, though, caffeine can enhance both speed and endurance by helping muscles contract with slightly more force. Caffeine in the form of sports drinks, soda or pills can improve endurance, he says, but coffee doesn't work. "Our only conclusion is that there must be factors in coffee that work in the opposite fashion," Graham says.

source:www.courant.com