With two-thirds of Americans drinking coffee daily, it’s no surprise that this beloved beverage is one of the most popular in the world. According to the National Coffee Association, coffee surpasses bottled water, tea, and even tap water as the top choice for Americans.

As a source of caffeine, which is considered safe for most healthy adults at a daily intake of about 400 milligrams, or four to five cups brewed at home, coffee has been linked to numerous health benefits, including a lower risk of mortality, based on large-scale studies that tracked participant behavior.

However, while research has indicated that moderate coffee consumption does not increase the risk of heart rhythm issues, certain medical societies still advise caution when it comes to caffeine consumption.

A recent study conducted on the effects of caffeinated coffee revealed that it had no significant impact on one type of heart palpitation that feels like a skipped beat. However, it did show a slight increase in another irregular heartbeat among those who consumed more than one cup per day. Additionally, the study found that coffee consumption was associated with increased physical activity and decreased sleep duration.

The study authors equipped 100 healthy volunteers, mostly under 40, with monitoring gadgets that continuously tracked their heart function, daily steps, sleep patterns, and blood sugar. Over two weeks, the volunteers received daily text messages instructing them to drink or avoid caffeinated coffee on specific days.

The findings were published in the New England Journal of Medicine.

According to Dr. Gregory Marcus, a cardiologist at the University of California, San Francisco, who specializes in treating heart arrhythmias, this study is rare as it directly measures the biological effects of consuming or abstaining from caffeinated coffee in the same individuals, and provides a dense array of data points.

They revealed that consuming caffeinated coffee did not lead to an increase in the frequency of premature atrial contractions, which are extra heartbeats that originate in the upper chambers of the heart. While these types of heartbeats are common and usually benign, they have been linked to the development of atrial fibrillation, a potentially harmful heart condition.

Additionally, the study revealed a small indication of premature ventricular contractions, an irregular heartbeat that originates in the lower chambers of the heart. Although these types of beats are usually harmless and common, they have been linked to an increased risk of heart failure. The researchers observed a higher frequency of premature ventricular contractions in individuals who consumed two or more cups of coffee per day, but not in those who drank less.

According to the study, individuals who drank coffee took approximately 1,000 more steps per day and slept for around 36 minutes less. Blood sugar levels did not show a significant difference. An intriguing finding was that individuals with genetic variations that accelerate caffeine metabolism experienced a lesser sleep deficit, whereas those with variants that slow down caffeine metabolism experienced a greater sleep loss.

Dr. Dave Kao, a health data expert and cardiologist at the University of Colorado School of Medicine who was not involved in the study, noted that the results may not be applicable to the general population since the study was conducted on a limited number of individuals for a short period of time. Nonetheless, Kao added that the study’s findings are consistent with other research indicating that coffee is safe, and the study provides a controlled examination of caffeine’s impact.

One of the co-authors, Marcus, warns that the effects of coffee consumption can vary among individuals. He advises patients with heart arrhythmias to conduct their own experimentation to determine how caffeine affects them.

“They’re often delighted to get the good news that it’s OK to try coffee and drink coffee,” he remarked.

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