Caffeine, Your Heart and Exercise

One of the most common comments that I receive in seeing a new patient with a heart rhythm disorder is “when my heart started racing (or skipping beats) I stopped drinking anything with caffeine.” There seems to be a general perception that caffeine can irritate the heart. The use of caffeine may be at an all-time high in today’s society as it is in many drinks, energy supplements, exercise regiments, coffee, and some teas.

Caffeine is a natural product that is extracted from the raw fruit of coffee plants (over sixty species), kola nuts, cocoa, yerba maté, guarana berries, coffee beans and teas. Caffeine is rapidly absorbed in about 30-60 minutes in our bodies after ingestion.

Caffeine and Your Heart

The question behind the comment I often encounter in clinic is “does caffeine effect my heart?” The simple answer is that it does. Caffeine in high doses raises your blood level of epinephrine. Epinephrine is also known as adrenalin. In pure forms, epinephrine can increase blood pressure, increase the contractility or force of the heart, and mildly increase the heart rate. In patients that are susceptable to abnormal heart rhythms, high doses can cause the heart to develop skipped beats from the upper or lower heart chambers or palpitations from a rapid heart rhythm (1).

In most patients that I meet, when high doses of caffeine are consumed, there can be an uncomfortable feeling of the heart beating. This is usually due to a mildly elevated heart rate and increased force of each heartbeat. These are normal responses of the heart when exposed to epinephrine, but they can lead to uncomfortable symptoms. With normal heart responses the symptoms typically improve when the body levels of caffeine diminish. Unfortunately, if the caffeine causes the heart to beat abnormally, the abnormal heart rhythm can persist even after the body levels of caffeine are very low or even absent.

For most people that enjoy caffeinated products our bodies develop tolerance to caffeine over time and the effects on the heart are lessened. Unfortunately for most patients that have consumed caffeine for many years without significant changes, the development of new abnormal heart rhythms is usually independent of the caffeine. However, it is always a good idea to consider a trial of stopping caffeinated products if you experience an abnormal heart rhythm or any new heart symptoms.

When considering your caffeine courses, caffeine that has been extracted or developed as a chemical, dry product, or pill appears to be more potent in our bodies compared to natural sources of caffeine. For example, the metabolism and exercise performance effects with caffeine are greater with caffeine pills compared to coffee that has a similar level of caffeine (2).

Caffeine and Exercise

There are many studies that have examined the impact of caffeine during exercise. When interpreting these studies you must take into account that they were performed in people that were often athletes with healthy hearts and may not apply to people with heart disease. Recently, the Journal of the International Society of Sports Nutrition summarized the effects of caffeine on exercise:

“1. Caffeine is effective for enhancing sport performance in trained athletes when consumed in low-to-moderate dosages (~3-6 mg·kgBM^-1) and overall does not result in further enhancement in performance when consumed in higher dosages (= 9 mg·kgBM^-1).

2. Caffeine exerts a greater ergogenic effect [enhancing exercise performance] when consumed in an anhydrous state [contains no water or pill form] as compared to coffee.

3. Caffeine enhances alertness during periods of extended exhaustive exercise, as well as periods of sustained sleep deprivation.

4. Caffeine is ergogenic for sustained maximal endurance exercise, and has been shown to be highly effective for time-trial performance.

5. Caffeine supplementation is beneficial for high-intensity exercise, including team sports such as soccer and rugby, both of which are categorized by intermittent activity within a period of prolonged duration.

6. The literature is equivocal [unclear or ambiguous] when considering the effects of caffeine supplementation on strength-power performance, and additional research in this area is warranted.

7. The scientific literature does not support caffeine-induced diuresis [increased urination] during exercise, or any harmful change in fluid balance that would negatively affect performance” (3,4).

When you look at the total evidence available, in low to moderate levels, caffeine will likely result in an improvement in both your aerobic exercise ability and tolerance and may also provide benefit in resistance exercise (4).

In conclusion, if you feel abnormal heart beats or rhythms if you start using caffeine or start using high doses then stop using it. You may have to wait days after the caffeine exposure for your heart to go back to normal. If it doesn’t or the symptoms are severe, you should contact your doctor. If you develop these symptoms after years of using similar levels of caffeine, then your heart symptoms are likely caused from other sources. If you use caffeine to improve your exercise ability, use relatively low doses. The accumulative evidence with low to moderate amounts of caffeine and exercise suggests it is beneficial and relatively safe. If you have prior heart disease or abnormal heart rhythms, talk to your physician before starting an endurance exercise program in which you want to also use caffeine to enhance your performance.