Coffee lovers, watch your heart!

Coffee is the most popular drink in the world and many studies have pointed to its benefits. At the cardiac level, its regular consumption would reduce the risk of death from heart disease, stroke and premature death. In the short term, however, drinking a cup of coffee can make it difficult to fall asleep and lead to irregular heartbeats. This was concluded by researchers from theAmerican Heart Association in a study presented on the occasion of their annual scientific session which took place between 13 and 15 November.

Studying the real-time effects of coffee

For this study, scientists sought to observe the direct effects of coffee on consumers. “Coffee is the most consumed beverage in the world, but its health effects remain unclearsays Gregory Marcus, lead author of the study. While the majority of long-term observational studies have suggested multiple potential benefits of coffee consumption, this is the first randomized trial to investigate the real-time physiological consequences of coffee consumption..”

For their research, the study authors gathered 100 adults whom they followed using continuously recording ECG machines to monitor heart rhythm while drinking caffeinated coffee. The volunteers also wore wrist devices to track physical activity levels and sleep duration. Continuous glucometers tracked each person’s blood sugar levels during the experiment, which lasted two weeks. The researchers also took saliva DNA samples from each person to see if the impact of coffee consumption depends on a person’s ability to metabolize caffeine. During the two-week follow-up, the team randomly asked each participant not to drink coffee for two consecutive days, before resuming it. Each person also completed a questionnaire, revealing how much coffee they drink in the morning and throughout the day.

The good and the bad of coffee

The results show that coffee consumption leads to a 54% increase in premature ventricular contractions, a type of irregular heartbeat that occurs in the lower chambers of the heart. When this happens, people feel like their heart has skipped a beat. The increase in caffeine negatively impacted time spent sleeping. On average, the volunteers slept 36 minutes less after consuming coffee. For every cup of coffee consumed, participants slept 18 minutes less the following night.

On the positive side, people who drank more coffee reported having fewer episodes of supraventricular tachycardia, which is a rapid heartbeat in the upper chambers of the heart. The study authors find that the daily increase in caffeine leads to more physical activity. Coffee drinkers recorded more than 1,000 extra steps compared to days when they did not drink coffee. For every extra cup of coffee they drank, participants took almost 600 extra steps during the day. Finally, the study found no noticeable change in blood sugar on the days the group avoided or drank coffee.

Coffee and health, a complex relationship

“More physical activity, which appears to be driven by coffee consumption, has numerous health benefits, such as reduced risks of type 2 diabetes and several cancers, and is associated with greater longevityreported Gregory Marcus. On the other hand, reduced sleep is associated with a variety of adverse psychiatric, neurological, and cardiovascular outcomes. More frequent abnormal heartbeats from the upper heart chambers influence the risk of atrial fibrillation, and more frequent abnormal beats from the lower chambers, or ventricles, increase the risk of heart failure. These results highlight the complex relationship between coffee and health.”

Do the benefits of coffee depend on your genes?

Using the DNA samples, the team found that coffee drinkers with genetic variants that create faster caffeine metabolism have more irregular heartbeats. Conversely, the slower a person’s genes metabolized caffeine, the more those people lost sleep after drinking coffee.