Have You Gone Caffeine Crazy?

When the Buzz Goes Bad

But too much caffeine -- especially if you don't recognize your threshold -- can have substantial health risks. The reason coffee and other caffeine sources rev us up is that they raise adrenaline -- up to 32 percent over normal levels -- according to a series of studies led by Dr. Lane. While this can temporarily boost energy, it can also trigger heart palpitations, temporarily raise blood pressure, and lead to insomnia. "Caffeine keeps people awake by preventing the brain from recognizing when it's tired, which disrupts our natural sleep patterns," says Dr. Lane, who has studied caffeine for nearly 20 years.

Whereas moderate caffeine consumption has energy and alertness benefits, excessive consumption seems to tip the scales. Drinking more than five cups of non-gourmet coffee a day (people in Dr. Lane's study drank 500 milligrams of caffeine) can exaggerate the effect of stress and magnify a person's response to pressure. This can leave you tired and cranky, impairing your ability to handle difficult situations calmly. "A stressful day is made more stressful by high doses of caffeine, which increase the feelings of being burned-out and depleted," says Dr. Lane. This makes caffeine a bad choice for those prone to depression or anxiety disorders.

For people who are slow to metabolize caffeine (see "Could Caffeine Be a Health Risk?"), the substance can be dangerous. And some ultra-high-caffeine products can be risky, period. From January 2004 to June 2006 California poison-control center toxicologists reported 10 calls from people (age range: 13 to 53) who ingested one to two 8-ounce cans (250 milligrams of caffeine each) or two or more teaspoons of powdered concentrate (250 milligrams per teaspoon). Four wound up in the ER. And Chicago poison-control officials noted an emerging caffeine-supplement abuse problem among young people, putting 31 of more than 250 poison-control center callers in the hospital. Overdose can cause chest pain, heart palpitations, tremors, sweating, nausea and neurologic symptoms, notes the American College of Emergency Physicians.

Does caffeine upset the stomach? Research on this is mixed, says William D. Chey, MD, an associate professor of medicine at the University of Michigan in Ann Arbor, who recommends having no more than one cup a day to avoid heartburn. Folgers Simply Smooth, one of a growing line of "stomach friendly" brands, comes in caffeinated and decaf versions designed to avoid the problem.