Can Caffeine Slow the Heart Rate?

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If you're like the average American, your day cannot start without sipping on a hot cup of coffee. The caffeine in coffee stimulates your brain and makes you feel awake, but it also is causing other affects in your body. Caffeine does not slow the heart rate; it actually increases it and can even cause stress to your cardiovascular system all day long.

Caffeine and Heart Rate

Caffeine is a stimulant derived from the leaves as well as the seeds of plants. It is most commonly found within coffee but also can be in tea, chocolate and some medications. The stimulant effects of caffeine help to increase your alertness, cardiovascular system and even your brain function. In the case of the cardiovascular system, caffeine increases your heart rate.

Nervous System

The caffeine molecule inside the brain appears to the brain much like a naturally made chemical transmitter known as adenosine. When caffeine binds to the adenosine receptors inside the brain, it stimulates the sympathetic nervous system and elicits a fight or flight response. Part of this response is an increase in heart rate. According to a study published by the Duke University Medical Center in 1999, caffeine has the ability to increase blood pressure and stress responses such as those listed above all day. This study monitored the body's response to caffeine in 72 coffee drinkers. Over two weeks, participants drank coffee some days and abstained from it other days. On both days, hormonal and cardiovascular responses were monitored. Researchers discovered that caffeine elicits stress responses all day, increasing blood pressure and stress hormones.


Caffeine has a diuretic-like effect on your body when you consume large amounts. This means that it increases the amount of urine your body is producing. Unless you counteract this by increasing your fluid intake, you risk suffering from dehydration. Dehydration can affect your heart. A symptom of dehydration is an increased heart rate.

Other Negative Effects

Not only does caffeine increase heart rate, but overuse or consumption by those particularly sensitive to caffeine might cause certain heart arrhythmias. Furthermore, caffeine can increase blood pressure by three to 14 points for systolic pressure and four to 13 points for diastolic pressure, states Sheldon G. Sheps, M.D., on Either of these conditions might be hard on the heart, particularly for a person with known cardiovascular problems.


According to Sheps, most people can take in about 200 mg of caffeine per day without any negative side effects. This amount is equal to the caffeine inside of two 12 oz. cups of coffee, but you might want to check with your doctor regarding the appropriate amount of caffeine for your condition.