(LifeWire) - What we know about caffeine and heart disease is a mixed brew, but here is the bottom line: A couple of cups of coffee a day has little effect on most people with heart disease or those at risk for it. In fact, some studies suggest it could actually be beneficial.
Caffeine can be produced synthetically, but mainly it's derived from the beans, leaves and fruits of certain plants. It can be consumed in several ways, most obviously in coffee. Even decaffeinated coffee is not entirely free of caffeine. But you might be surprised to hear that the popular "energy drinks" rival coffee as heavy-duty sources of caffeine
Here's a rundown of just about how much caffeine there is in each of the following:
- Energy drinks have about 72 to 150 mg of caffeine per serving. Many bottles contain 2 to 3 servings of caffeine.
- Coffee has 60 to 150 mg of caffeine per cup.
- Over-the-counter medications have up to 65 mg of caffeine for pain killers. Caffeine is also commonly found in appetite suppressants and many cold and cough remedy medicines.
- Colas have 47 to 64 mg of caffeine per 12-ounce can.
- Tea has 40 to 80 mg of caffeine per cup.
- Chocolate bars have up to 35 mg of caffeine per ounce.
- Cocoa has up to 8 mg of caffeine per cup.
- Decaffeinated coffee has up to 7 mg of caffeine per cup.
According to the American Heart Association, one to two cups of regular coffee -- which contains 120 mg to 300 mg -- is fine, but more than that could be risky. Caffeine increases urination, which could result in dehydration. Caffeine also stimulates the nervous system, which speeds up the heart rate.
Caffeine has been linked to other heart problems, such as inducing mild arrhythmia, which is an irregular heartbeat. And according to a 2006 study in the journal Epidemiology, caffeine can contribute to a heart attack.
On the other hand, a 2007 study in the American Journal of Clinical Nutrition found that people over age 65 who consume caffeine are less likely to die of heart disease.
Another study found that drinking one to three cups of coffee actually lowers your heart rate during light exercise.
If you're a heart patient, or you're at risk for heart disease, your doctor can help you decide whether or not limited caffeine consumption would be advisable.Here's more on caffeine and heart disease.
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Greenberg, James A., Christopher C. Dunbar, Roseanne Schnoll, Rodamanthos Kokolis, Spyro Kokolis, and John Kassotis. "Caffeinated Beverage Intake and the Risk of Heart Disease Mortality in the Elderly: A Prospective Analysis." American Journal of Clinical Nutrition 85:2(2007):392-8. 6 Nov 2008. <http://www.ajcn.org/cgi/content/full/85/2/392>.
McClaran, Steven R., and Thomas J. Wetter. "Low Doses of Caffeine Reduce Heart Rate During Submaximal Cycle Ergometry." Journal of the Interrnational Society of Sport Nutrition 4:(2007):11. 6 Nov. 2008. <http://www.jissn.com/content/4/1/11>.
McCusker, Rachel R., Brian Fuehrlein, Bruce A. Goldberger, Mark S. Gold, and Edward J. Cone. "Caffeine Content of Decaffeinated Coffee." Journal of Analytical Toxicology 30:8(2006):611-3. 6 Nov. 2008. <http://www.jatox.com/abstracts/2006/october/611-goldberger.html>. (subscription)
"Neuroscience for Kids -- Caffeine." faculty.washington.edu. 2008. University of Washington. 6 Nov. 2008. <http://faculty.washington.edu/chudler/caff.html>.