This article discusses the potential cardiovascular risks associated with consuming over 400 mg of caffeine daily, including increased heart rate and blood pressure.

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A morning cup of coffee is a popular way to start the day. But too much of a good thing could mean problems for the heart.

Research presented at the annual American College of Cardiology Asia meeting found that drinking more than 400 mg of caffeine every day on most days of the week can raise the risk of cardiovascular disease in otherwise healthy people.[1]

“Regular caffeine consumption could disturb the parasympathetic system, leading to elevated blood pressure and heart rates,” said lead study author Nency Kagathara, MBBS, of Zydus Medical College and Hospital in a press statement.[2] 

“Our study sought to determine the effects of chronic caffeine consumption on heart health, specifically the recovery of heart rate and blood pressure.”

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About the study 

In undertaking their study, the researchers enlisted a group of 92 normotensive and healthy individuals between the ages of 18 and 45.

The researchers noted the participants’ sociodemographic information and daily caffeine intake. The participants had their heart rate and blood pressure measured and undertook a 3-minute step test.

Following the 3-minute step test, blood pressure and heart rate readings were taken again at 1- and 5-minute intervals.

This equates to roughly four cups of coffee, two energy drinks, or 10 cans of soda. The authors defined chronic caffeine consumption as the intake of any caffeinated beverage 5 days a week for over a year.

The study specifically focused on caffeinated beverages like coffee, tea, and aerated drinks like Coke, Monster, Pepsi, Red Bull, and Sting.

Those who consumed more than 600 mg of caffeine every day showed a significant association with an elevated heart rate of 100 beats per minute and a blood pressure reading of >140/90 mm Hg after 5 minutes of rest following the step test.[1]

“Due to its effect on the autonomic nervous system, regular caffeine consumption could put otherwise healthy individuals at risk of hypertension and other cardiovascular events,” Kagathara said in a press statement.[2]

“Increasing awareness of these risks is vital to improve heart health for all.”

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The importance of moderation

Beth Abramson, a member of the American College of Cardiology Prevention Council and the Paul Albrechtsen Professor in Cardiac Prevention and Women’s Health in the Division of Cardiology at St. Michael’s Hospital at the University of Toronto, says the study is an important reminder of healthy lifestyle choices but does not mean people need to cut out caffeine.

“[The study] does not mean that drinking coffee in general and in moderation is necessarily bad for you. We have no evidence for that, but we do know that this heavy caffeine intake was associated with higher blood pressure, and we do know that we can lower blood pressure with lifestyle changes,” she said.

“This study does suggest that excess caffeine may not be a good thing for the heart, and it may not be good for us. And I would argue that excess of anything in our diet, except for healthy fruits and vegetables, truly isn't good. I think we have to think about moderation when we're planning our meals and when we're eating and when we're living,” she adds.

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How much caffeine is safe?

The United States Food and Drug Administration says that healthy adults can consume up to 400 mg of caffeine a day without negative effects.[3] That is the equivalent of roughly four or five cups of coffee.

Overconsumption can cause a variety of side effects, including headache, nausea, insomnia, jitters, and a fast heart rate.

“In America, we don't recommend patients ingest over 400 milligrams of caffeine daily. It is considered a threshold. [Caffeine] is a stimulant, and so it can increase the workload of the heart because it is causing, perhaps, constriction of blood vessels; it's increasing heart rate, and so it can have adverse cardiovascular effects. But I don’t think that’s with just a little bit of caffeine a day,” said Parveen Garg, MD, a cardiologist at Keck Medicine of USC.

Both experts say that moderation of caffeine consumption is important. Dr Garg argues that reasonable amounts of coffee may even benefit heart health.  

“It's pretty well-established [in] multiple studies that moderate coffee consumption is associated with a decreased risk of cardiovascular mortality and cardiovascular disease. So it isn’t that caffeine is all bad. This study confirms or adds to the growing evidence that very high levels of caffeine can be damaging, but just having caffeine, particularly with coffee or tea…actually can have beneficial effects on your heart.”

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Disclaimer: This story is contributed by Elizabeth Pratt and is a part of our Global Content Initiative, where we feature selected stories from our Global network which we believe would be most useful and informative to our doctor members.