How Caffeine Works

Caffeine can be found in many weight loss pills to boost the metabolism. But there are a number of additional situations where caffeine can serve important medical uses.

Caffeine that has been citrated -- treated with a citrate of potassium or sodium -- can help breathing in premature babies. Young children who suffer breathing problems after surgery may also benefit from medical treatment with caffeine [source: Kovacs].

For adults, caffeine is sometimes used to kick-start other medications. It improves the effectiveness of aspirin or acetaminophen, and is used with a drug called ergotamine to treat cluster and migraine headaches. Research suggests that caffeine's ability to cause blood vessels to constrict blood flow -- as we'll discuss in the next section -- may play a role in causing these effects.

There have been more than 19,000 studies on caffeine and coffee in the past 30 years, most of which have aimed to uncover the drug's exact effects on the human body. One of the most thorough and exhaustive studies was done by Harvard University, involving 126,000 people over an 18-year period.

The findings from the Harvard study may seem surprising: They indicate that people who drink one to three cups of coffee a day are up to 9 percent less likely to contract diabetes than those who don't. For subjects who drank six or more cups of coffee per day, men slashed their chances of contracting diabetes by 54 percent, and women by 30 percent [source: Kirchheimer].

We'll explore more of the research into caffeine's benefits in a bit, but for now it's important to note that most Americans consume the bulk of their caffeine -- intentionally or not -- as a form of self-medication. Grabbing a cup of coffee when they need a pick-me-up, for example, or sipping an energy drink to keep going at the end of a long day puts many drinkers into the higher levels of FDA-recommended daily limits of the drug. Given the way this kind of consumption can affect the body, caffeine is an important drug to understand the workings of. Read more about how caffeine affects the body and brain on the next page.