The State of Coffee in the CCU

I have heard some chatter among the patients on the cardiac care unit regarding whether they may safely indulge in a daily cup of joe. I have also noticed that when providers are placing diet orders, there is an option for decaffeinated vs caffeinated coffee. As a curious, caffeinated medical student, I found myself asking what exactly are the cardiac risks associated with coffee and caffeine? 

The history of coffee is marred by unsubstantiated claims that it is harmful to human health. However, there is growing evidence and increasing acceptance of coffee’s health benefits, including: improved mood and concentration^1,2, decreased risk of dementia³, as well as decreased risk of diabetes^4,5, and cancer among other benefits attributed to its antioxidant effects^6,7. Furthermore, some analyses have demonstrated coffee to be inversely associated with mortality⁸.These studies by no means establish coffee as a panacea. However, they call into question the practice of depriving patients one of life’s simple pleasures in the name of health. 

The exact origins of theorized cardiac risks of coffee remain unclear. However, studies began emerging on the topic in the 1960s⁹.  By the 1980s numerous studies were published demonstrating an association with poor cardiovascular health. Some of the specific outcomes measured include hypertension, hyperlipidemia, and arrhythmias^10,11. The conclusions of subsequent meta-analyses did not show consistent correlations. However, the idea that coffee is bad for the heart prevailed throughout this period. 

One of the most notorious claims is that coffee induces or exacerbates cardiac arrhythmias. A survey of 697 providers from 1988 revealed that 80-90% recommended moderating caffeine intake in patients with known tachycardia, palpitations, and arrhythmia, yet it is unclear how this consensus arose¹². On evaluation of the medical literature of 2022, it seems clear that a positive correlation between arrhythmias and caffeine does not exist. If anything, recent analyses demonstrate a protective effect^13,14.  For example, a recent prospective cohort study of over 400,000 individuals revealed that each additional daily cup of coffee was associated with a 3% reduced risk of developing an arrhythmia¹⁵.

There are a few proposed mechanisms for this phenomenon. The most popular of which seems to be the activity of caffeine on adenosine receptors. Caffeine is known to block adenosine receptors, which results in a prolonged left atrial refractory period, effectively reducing the likelihood of atrial arrhythmias. Coffee’s antioxidant effects may also play a role, as it is known that inflammation can lead to arrhythmias via multiple pathways. Lastly, although it may seem counterintuitive, the catecholaminergic properties of caffeine may be protective against PVCs, as well as certain arrhythmias triggered by enhanced vagal tone. Research remains ongoing regarding the physiologic effects of caffeine on the cardiac conduction system.

Although arrhythmias are the most cited adverse cardiac outcome among coffee drinkers, hypertension and hyperlipidemia have also been implicated¹⁰. Studies have been unanimous in detecting slight increases in both systolic and diastolic blood pressures for up to 3 h after caffeine ingestion¹⁷. Although it of note, that studies which implicated coffee in elevated blood pressures and increased stroke risk were performed among non-coffee drinkers or participants who had abstained from caffeine intake prior to the study. This is an important distinction because it has been established that humans develop caffeine tolerance quite quickly, and the same risks were not observed among habitual drinkers or research participants with prolonged exposure¹⁸. In fact, some studies show that habitual consumption of coffee or tea may reduce risk of hypertension due the actions of phenolic compounds, specifically chlorogenic acids¹⁷.

An interesting distinction has been made regarding the effects of coffee on lipid levels. It appears to be dependent on the brewing method. Boiled coffee is associated with a rise in cholesterol, while drinking filtered coffee is not. This is because boiling methods extract more diterpenes from beans and fail to filter them out from the result¹⁷.  The clinical relevance of this distinction is unclear. Overall caffeine has a favorable metabolic profile, as it increases resting metabolic rate and energy expenditure and promoting cellular thermogenesis and lipolysis¹⁹. 

Based on current data, it appears that coffee does not pose an imminent threat to cardiovascular health. Future research into the potential benefits of coffee is ongoing and will provide further insight on how to best counsel patients. Considering that on average, it takes approximately 17 years for cardiovascular research to translate to changes in clinical practice²⁰, it is understandable that patients with heart disease continue to approach coffee with caution. It is important for providers to counsel patients on the risks and benefits of caffeinated drinks, which are a morning ritual for many.  It may be of particular importance in the CCU, where many patients are already struggling to implement other lifestyle and dietary changes to benefit their cardiac health.

Katherine Bracamontes

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Katherine Bracamontes is a student at The University of Arizona College of Medicine-Phoenix class of 2023. She graduated from the University of Southern California in 2015 with a B.S. in Lifespan Health. While living in California she became involved with her local radio station, which fostered an interest in community culture and journalism. Katherine enjoys live music and hiking at a very, very leisurely pace.

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