Coffee’s Harmful Short-Term Health Implications

A recent review conducted by the American Heart Association (AHA) sheds light on the health benefits of coffee, specifically its impact on premature ventricular contractions and physical activity levels. The study, performed at the University of California, San Francisco, explored the dual nature of caffeinated coffee’s effects on health, revealing both positive and negative outcomes.

 Coffee’s Dual Effects on Heart Health and Physical Activity

 According to the American Heart Association, drinking caffeinated coffee can have both beneficial and harmful short-term health effects. On the downside, coffee consumption is associated with increased abnormal heartbeats and reduced sleep duration. On the upside, it boosts physical activity and may lower the risk of cardiovascular disease.

 Study author Gregory Marcus, M.D., M.A.S., associate chief of cardiology for research and endowed professor of atrial fibrillation research at the University of California, San Francisco, remarked, "Coffee is the most commonly consumed beverage in the world, yet its health effects remain uncertain." He added, "While the majority of long-term observational studies have suggested multiple potential benefits of drinking coffee, this is the first randomized trial to investigate the real-time, physiologic consequences of coffee consumption."

 The Study Devices and Cohort

 Dr. Marcus and his team enrolled 100 adult volunteers who were assigned to wear several monitoring devices for two weeks:

 · ECG devices to continuously track heart rhythms

· Fitbits to monitor physical activity and sleep

· Glucose monitors to track blood sugar levels

 Participants had an average age of 38 years, with 51% being women and 48% being white. DNA saliva samples were collected to assess genetic variants affecting caffeine metabolism. The participants were randomly assigned to either avoid coffee or consume it for no more than two consecutive days over 14 days. Coffee and espresso consumption were logged in real-time using a "time stamp button" on the ECG monitor, with additional geo-tracking of coffee shop visits and daily questionnaires.

 The Results

Data analysis revealed that coffee consumption was linked to a 54% increase in premature ventricular contractions (PVCs), an abnormal heartbeat originating in the heart’s lower chambers often felt like a skipped heartbeat. However, more coffee intake was also associated with fewer episodes of supraventricular tachycardia, a rapid heart rhythm arising from the upper chambers.

 Dr. Marcus clarified, "PVCs are common and are usually regarded as harmless. We all have them once in a while, and generally they're considered benign. But we and others have shown that more PVCs are an independent risk factor for heart failure over time. Not everyone with more PVCs has heart failure, but it is a factor."

 Sleep, Activity, and Heartbeats: Understanding Coffee’s Impact

 Coffee consumption consistently resulted in more physical activity and less sleep:

 · Participants who drank coffee logged over 1,000 additional steps per day compared to non-coffee days.

· On coffee-drinking days, participants slept 36 fewer minutes per night, according to their Fitbits.

· Drinking more than one coffee drink doubled the number of irregular heartbeats from the heart’s lower chambers.

· Each additional cup of coffee was linked to nearly 600 more steps per day and 18 fewer minutes of sleep per night.

· No differences were observed in continuously recorded glucose levels between coffee consumption and avoidance days.

 These findings were corroborated by adherence analyses and were more pronounced with higher coffee consumption. Dr. Marcus noted, "More physical activity, which appears to be prompted by coffee consumption, has numerous health benefits, such as reduced risks of Type 2 diabetes and several cancers, and is associated with greater longevity. On the other hand, reduced sleep is associated with a variety of adverse psychiatric, neurologic, and cardiovascular outcomes."

 The study also found that genetic variants influencing caffeine metabolism affected the frequency of abnormal heartbeats and sleep duration. Those with faster caffeine metabolism exhibited more PVCs with increased coffee intake, while slower metabolizers experienced more sleep loss.

 Dr. Marcus emphasized, "Because coffee was randomly assigned to the study participants, cause-and-effect can be inferred. These observations were made during repeated assessments of days when coffee was consumed versus when it was not, eliminating concerns regarding differences in individual-level characteristics as an explanation for these results."

 While this study involved 100 participants over two weeks, previous research involving 382,535 participants over ten years found that drinking two to three cups of coffee daily was associated with the greatest benefit, including a 10%-15% lower risk of developing coronary heart disease, heart failure, heart rhythm problems, or dying for any reason. The maximum benefit was seen among those drinking two to three cups of coffee per day, highlighting a U-shaped relationship with coffee intake and new heart rhythm problems.

 The complex relationship between coffee and health underscores the importance of understanding both its positive and negative effects.