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College of Food, Agricultural, and Environmental Sciences


Chow Line: Caffeine OK, but can irritate stomach (for 10/28/07)

October 19, 2007

A colleague just experienced a bout of stomach flu. As she recovered, she said she felt OK as long as she didn't consume caffeine. Was it the caffeine or the coffee that upset her stomach?

Actually, it probably was the caffeine. While you might think that the coffee itself might have ill effects on a weak stomach (and sometimes, of course, it might), it's well known that caffeine in any form can irritate the stomach.

When food enters the stomach, it begins to dissolve and degrade thanks to the stomach's secretions of hydrochloric acid and other gastric fluid. These secretions can start before you even begin eating — just think of how your mouth waters at the sight or aroma of a favorite food. The stomach produces more acid when it stretches as food enters it. Other factors can also increase the production of stomach acid, and the presence of caffeine is a major one.

Coffee, tea, colas and other beverages can contain caffeine, although how much can be difficult to determine because caffeine content doesn't have to be listed on labels. Over-the-counter pain relievers also often contain caffeine — it is listed on those labels. If you're trying to relieve a headache but also have stomach problems, choose a pain reliever without caffeine.

Despite its effect on stomach acid, caffeine does not appear to be responsible for many of the ill effects it's often blamed for. For example:

  • Some studies have linked caffeine consumption with osteoporosis or bone loss. However, that appears to be true only for people with a certain genotype, and consuming enough calcium and vitamin D seems to eliminate the problem.
  • Caffeine is sometimes blamed for increased blood pressure and heart rate. But that's due to its mild stimulant effect, which varies among individuals and is temporary at most.
  • Caffeine is a diuretic, and so is sometimes thought to cause dehydration. But the effect is mild and temporary. In fact, according to a 2004 Institute of Medicine report on how much water people need on a daily basis, experts said coffee and other caffeine-containing beverages can be counted at least in part to help meet the daily requirement.

Still, too much caffeine can cause the jitters, including restlessness, anxiety and headaches. If you want more information on how much caffeine is in common beverages and other products, is a good resource. Just go to the site and search for "caffeine," and click on "How much caffeine is in your daily habit?"

Chow Line is a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH, 43210-1044, or

Editor: This column was reviewed by Marti Andrews, registered dietitian and adjunct associate professor in the Department of Human Nutrition, College of Education and Human Ecology.

Martha Filipic
Marti Andrews