Caffeine has multiple physical effects TO YOUR HEALTH


December 22, 1992|By Dr. Genevieve Matanoski | Dr. Genevieve Matanoski,Contributing Writer

Scientists call it 1-3-7 trimethylxanthine, and it is the most widely used psychoactive substance in the world. You probably had it for breakfast.

To most of us, it is caffeine. Researchers like Dr. Roland Griffiths, professor of psychiatry and neurosciences at the Johns Hopkins University School of Medicine, are particularly interested in how caffeine affects our bodies and behavior.

Q: What are the usual dietary sources of caffeine?

A: It is a substance found naturally in coffee, tea and cocoa products. It is added to soft drinks. Caffeine also is in many over-the- counter medications, such as analgesic compounds, which is why it is important to read labels if you want to avoid it.

Q: How does caffeine work?

A: The most well-accepted current hypothesis is that caffeine interacts with a central nervous system chemical, adenosine, that regulates body functions. The results may be increased alertness or nervousness, frequent urination, rapid and possibly irregular heartbeat, increased gastric secretions which can aggravate ulcers, bronchial muscle relaxation which can help breathing and changes in the constriction of blood vessels.

Q: Does caffeine affect men and women in the same ways?

A: A major difference seems to be that women on oral contraceptives and women in the final weeks of pregnancy eliminate caffeine more slowly and therefore retain it in their bodies about twice as long as other adults. Ordinarily, within 24 hours of drinking caffeine, men and women eliminate it in their urine. The slowed elimination rate in pregnant women may explain why some women lose their desire for caffeine during pregnancy. Immediately after delivery, the elimination rate returns to normal.

It also is known that many smokers do not accumulate caffeine in their bodies because they eliminate it more rapidly than non-smokers. That may be why it is not unusual for smokers to drink large amounts of coffee.

Q: What about children?

A: Newborns eliminate caffeine slowly. From ages 1 to 11 the process speeds up, after which it reaches adult rates.

Q: What happens to us when we try to cut back on caffeine?

A: From 10 to 50 percent of the people who consume caffeine regularly show some significant signs of withdrawal when they abruptly quit. They may have headache, lethargy, depression, anxiety. In the most severe cases, they may also experience flu-like symptoms, including muscle aches, nausea and even vomiting.

The symptoms generally begin within 12 to 24 hours and will peak at 24 to 48 hours. They gradually taper off over about a week.

In many instances, post-operative headaches are from caffeine withdrawal rather than anesthesia or other medical problems. Physicians are paying more attention to their patients' history of caffeine use when they're under treatment.

Q: What is the best way to cut back?

A: Take your time. Gradually reduce your intake over a period of days or weeks. Mix caffeinated with decaffeinated coffee or tea, with the goal of eventually drinking only decaffeinated.

Q: What are the medical reasons for paying attention to caffeine levels?

A: Medical specialists recommend reducing or eliminating caffeine for people with anxiety, insomnia, palpitations, arrhythmia, tachycardia and esophagitis/hiatal hernia.

As Dr. Griffiths points out, research into caffeine is relatively new, but it has been a topic of political and economic speculation for many societies across centuries. English and Arab nations tried to make caffeine taboo, with little success. And if it weren't for the Boston Tea Party, the American caffeinated drink of choice would have been tea.

Dr. Matanoski is a physician and professor of epidemiology at the Johns Hopkins School of Hygiene and Public Health.

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