Caffeine is a known stimulant present in many dietary sources consumed around the world, i.e., in coffee, tea, cocoa, candy bars, soft drinks and energy drinks. The caffeine content of these various food sources can range from 4 mg caffeine/150 ml of cocoa to 71-220 mg caffeine/150 ml depending upon the method and duration of brewing.2 The most favored form of caffeine ingestion around the world is via coffee.3
Exercise intolerance and fatigue are prominent symptoms of heart failure that impact negatively on the well-being of individuals with heart failure. Researchers from the University of Toronto in Ontario, Canada used a randomized, placebo-controlled, double-blind crossover study design to determine whether caffeine increases exercise tolerance in heart failure patients. The study included 10 stable heart failure patients with impaired left ventricle systolic function and 10 healthy, age-matched, medication-free volunteers. All 10 of the heart failure patients were receiving conventional medical therapy.
Each participant in the study received an intravenous infusion of 4 mg caffeine/kg body weight (equivalent to 2 cups of coffee) diluted in 5% dextrose solution or the same volume of 5% dextrose without caffeine. Following infusion, the investigators measured the heart rate, blood pressure, and ventilation at rest and during graded cycling until peak effort (indicated by the inability to maintain pedal speed).
The authors noted that caffeine increased the duration of exercise to peak effort in patients with heart failure, but had no effect on exercise duration in healthy control subjects. Additionally, caffeine increased resting and peak blood pressuresin heart failure patients to a greater extent than in participants without heart failure.
Although there are no specific recommendations regarding the intake of caffeine in patients with heart failure, these findings support the conclusions of scientific research as well as the opinion of most physicians and nutritionists that moderate consumption of coffee (1-2 cups per day) appears to pose little or no increase to heart-related risk.
- Notarius CF, Morris B, Floras JS. Caffeine Prolongs Exercise Duration in Heart Failure. J Card Fail 2006;12:220-226.
- Eskelinen MH, Kivipelto M. Caffeine as a Protective Factor in Dementia and Alzheimer’s Disease. Journal of Alzheimer’s Disease 2010;20:167-174.
- Wang Y, Tuomilehto J, Jousilahti P et al. Coffee consumption and the risk of heart failure in Finnish men and women. Heart 2011;97:44-48.