The Effects of Caffeine on Heart Rate

Well over half of Americans drink an average of 3 cups of coffee per day, reports the Harvard School of Public Health. If you're not one of them, you might rely on cola or a chocolate bar as a pick-me-up. Coffee, chocolate, soda and tea all contain caffeine -- a mild stimulant. Caffeine causes various metabolic side effects, including increased heart rate and irregular heartbeat. Follow the recommended guidelines for caffeine intake to avoid unwanted consequences.

Caffeine Defined
Caffeine is a natural substance found in plants and an artificial substance added to foods. It stimulates your central nervous system and acts as a diuretic, causing you to excrete more fluids. Once consumed, caffeine is quickly absorbed and travels directly to your brain. You don’t store it, but rather excrete it through your urine within a couple of hours. According to the University of Michigan, you feel the effects of caffeine as quickly as 15 minutes, but they can endure up to six hours.

Caffeine in the Body
Adenosine is a naturally occurring chemical in your body. It connects to receptors in your brain, causing you to feel tired. But caffeine binds to the receptors so adenosine can’t fill them, and your brain increases its activity, which is why you feel more alert after consuming caffeine. Caffeine also affects chemicals in the body that signal your heart to pump harder and faster, causing an increase in heart rate.

Heart Arrhythmias
A heart arrhythmia is an abnormal heartbeat, including an unusually fast or slow heart rate, caused by underlying heart problems or other medical conditions. An arrhythmia can also occur in healthy hearts from medications or substances such as caffeine. You may not realize you have an arrhythmia, or you may feel a skipped heartbeat, pounding in the chest, dizziness, shortness of breath, chest discomfort or fatigue. Speak with your physician if you’re concerned, but your doctor may recommend limiting caffeine. The Cleveland Clinic reports that some individuals are more sensitive to the effects of caffeine and may notice an irregular heartbeat after caffeine consumption.

Considerations and Recommendations
Moderate caffeine consumption is typically not harmful for healthy adults. This includes two to three 8-ounce mugs of coffee or five servings of soda or tea. Limit your caffeine intake if you suffer from anxiety problems, painful breasts, acid reflux, high blood pressure, irregular heartbeat or headaches. If you're pregnant or breast-feeding, speak with your doctor before consuming caffeine. A 6-ounce cup of coffee contains 100 milligrams of caffeine; 1 ounce of unsweetened chocolate, 25 milligrams; 12 ounces of cola, 46 milligrams; and tea, 5 ounces of tea, 40 milligrams. If you choose to eliminate caffeine from your diet, you may experience withdrawal symptoms in the first 12 to 24 hours.