Addicted to coffee? Here’s how it can be harmful to your health

“Coffee is the most commonly consumed beverage in the world, yet its health effects remain uncertain,” says 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.

“While the majority of long-term observational studies have suggested multiple potential benefits of drinking coffee, this is the first randomised trial to investigate the real-time, physiologic consequences of coffee consumption.”

A new research has found that caffeinated coffee consumption can have both beneficial and harmful short-term health effects.

The findings were presented at the American Heart Association’s Scientific Sessions 2021.

The meeting was fully virtual Saturday from November 13-Monday to November 15, 2021, and was a premier global exchange of the latest scientific advancements, research and evidence-based clinical practice updates in cardiovascular science for health care worldwide.

Marcus and colleagues enrolled 100 adult volunteers, and they were assigned to wear continuously recording ECG devices (to track heart rhythm), wrist-worn devices to track physical activity and sleep; and continuous glucose monitors to track blood sugar levels for two weeks. The participants were an average age of 38 years, 51 per cent were women and 48 per cent were white. Researchers also obtained DNA saliva samples from the participants to assess genetic variants that may affect caffeine metabolism.

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Participants were then randomly assigned to either avoid or consume coffee for no more than two consecutive days each for 14 consecutive days. Coffee and espresso consumption were recorded in real-time via a “timestamp button” on the ECG monitor, and researchers tracked trips to coffee shops with geotracking. In addition, participants completed daily questionnaires to detail how much coffee they had consumed every morning.

The analysis found that coffee consumption was associated with a 54 per cent increase in premature ventricular contractions, a type of abnormal heartbeat originating in the lower heart chambers reported to feel like a skipped heartbeat. In contrast, drinking more coffee was associated with fewer episodes of supraventricular tachycardia, an abnormally rapid heart rhythm arising from the upper heart chambers.

Consuming coffee was consistently associated with more physical activity as well as less sleep. Specifically:

- Participants who consumed coffee logged more than 1,000 additional steps per day compared to days when they did not drink coffee.

- On the day participants drank coffee, they had 36 fewer minutes of sleep per night according to their Fitbit devices.

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

Marcus noted that 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 for each study participant, eliminating concerns regarding differences in individual-level characteristics as an explanation for these results.