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Effects of caffeine on heart health

How much is safe?

A cup of joe may be good for you, but don’t fall for the bull. The Red Bull, that is.

About half of U.S. adults age 20 or older are coffee drinkers. Coffee is the principal source of caffeine in this country, in addition to tea and soft drinks. Because it is a stimulant, the effects of caffeine on heart health are constantly being studied.

Benefits of your morning brewCaffeine image 320x320

Overall, the findings have shown that moderate coffee drinking of 1-2 cups per day is likely not harmful. Some studies have even shown beneficial effects of having up to 4 cups of coffee or tea, including reduced risk of heart failure, arrhythmias, stroke and type 2 diabetes; improvements in blood pressure; and reductions in all-cause mortality. However, the extent to which caffeine plays a role in these protective effects is still unclear. Coffee and tea are known to have high levels of antioxidants and phytonutrients, which protect the body’s cells and tissue like blood vessels and heart muscle. Therefore, more studies are needed to distinguish the benefits of the antioxidants from the effects of the caffeine.

Too much of a good thing

Despite the benefits of coffee and tea, it’s possible to have too much of a good thing. High levels of caffeine intake can be harmful. Consumption of five cups of coffee or more per day has been shown to significantly increase blood pressure — a risk factor for stroke and heart disease. Caffeine-containing energy drinks or “shots” have also been shown to increase blood pressure, with reports of hospitalizations and deaths related to consumption of these types of energy drinks. Although the connection is unclear, these products should be taken with caution. Energy shots often contain as much caffeine as two cups of coffee plus other compounds such as taurine or L-carnitine. Whether it’s the caffeine, other ingredients or their combination that causes adverse effects is not yet known.

How much caffeine are you getting?

Here’s a list of the approximate amounts of caffeine contained in the most common sources:

  • Coffee, brewed (8 fl oz): 95 mg
  • Espresso, brewed (1 fl oz): 64 mg
  • Tea, brewed (8 fl oz): 48 mg
  • Cola (12 fl oz): 30 mg
  • Red Bull (8.4 fl oz): 77 mg
  • 5-Hour Energy (2 fl oz): 200 mg
  • Cocoa mix, prepared ( 6 fl. oz): 5 mg
  • Chocolate bar (1 bar): 8 mg

Sources: FDA, Caffeine Intake by the U.S. Population, December 2012, and Mayo Clinic, Caffeine content for coffee, tea, soda and more.


Patterson-thumbJoyce B. Patterson, MPH, RDN, is a Clinical Dietitian, Cardiovascular Medicine at Domino’s Farms. She specializes in medical nutrition therapy for the treatment of hyperlipidemia, hypertension, diabetes, metabolic syndrome, weight loss and other risk factors for cardiovascular disease. She also provides group education for cardiac rehab patients and weight loss support groups. She completed her graduate studies in human nutrition at the University of Michigan School of Public Health (UMSPH) and completed the UMSPH Dietetic Internship in winter 2013.

Frankel-informal-vertical-sigThe University of Michigan Samuel and Jean Frankel Cardiovascular Center is the top-ranked heart and heart surgery program among Michigan hospitals. To learn more, visit our website at umcvc.org.