American Heart Association Weighs In on Coffee Drinking

— Scientific statement reviewed mostly observational evidence about safety and possible benefits

Caffeine consumption can be safely tolerated in reasonable amounts in most people, according to a review by the American Heart Association (AHA).

“The convergence of evidence from large cohort studies and small randomized controlled trials supports the conclusion that moderate caffeine or coffee consumption (up to 400 mg/d caffeine or ≈3 to 5 cups of coffee at 8 oz per cup) is safe for most adults and is associated with lower risk of cardiovascular disease, including coronary heart disease, stroke, heart failure, and AF [atrial fibrillation], as well as hypertension and type 2 diabetes,” wrote Gregory Marcus, MD, MAS, of the University of California San Francisco, and colleagues in Circulation.

The AHA writing group cited large prospective cohort studies with long-term follow-up that consistently showed modest inverse associations between habitual coffee consumption and all-cause mortality across diverse populations. The lowest mortality risk was observed around 2 to 4 cups of coffee daily, whether caffeinated or decaffeinated, according to the authors.

Outside the realm of cardiovascular health, coffee has also been linked to supposed benefits in cancer, liver health, and mental disorders, albeit not conclusively.

As for coffee’s links to specific cardiovascular effects, the evidence was also too complex for a straightforward AHA endorsement of a specific health benefit:

• Blood pressure: Prospective cohort studies suggested an inverse J-shaped relationship between habitual coffee consumption and hypertension, with an increased risk with intake of 1 to 3 cups per day but a trend toward a decreased risk with higher consumption.
• Diabetes: Habitual coffee consumption has been consistently associated with a lower risk of incident type 2 diabetes in observational cohort studies, but this may be unrelated to caffeine itself.
• Lipids: Unfiltered coffee (e.g., French press, Greek/Turkish, and Scandinavian boiled coffee) raised LDL cholesterol based on controlled trials.
• Coronary artery disease (CAD) and heart failure (HF): Caffeine, namely coffee, has been shown either to have no relationship or to be associated with a lower risk of these cardiovascular diseases in observational analyses. Around 1.5 to 3.5 cups a day of coffee consumption was associated with an approximately 10% lower CAD risk, while the lowest HF risk has been reported to be roughly 4 cups of coffee per day.
• Arrhythmias: Randomized controlled trial data showed that in regular caffeinated coffee drinkers, caffeinated coffee consumed at around 1 to 3 cups per day decreases the risk of atrial fibrillation occurrence but increases the frequency of premature ventricular contractions. Less evidence was available on supraventricular tachycardia, though results lean toward a reduced risk among caffeine consumers.
• Stroke: Moderate caffeine consumption has had a U-shaped association reported with stroke, with the lowest risk observed at moderate coffee consumption (3 to 4 cups/day). However, 4 or more cups of ground, instant, and decaffeinated coffee was also associated with a lower risk in another study; this modest inverse association was also seen for black and green tea.

“Although research suggests that caffeine consumption may be associated with certain cardiovascular benefits for some people, it’s important to remember that there is no ‘one-size-fits-all’ strategy for safe caffeine consumption. People can respond very differently to caffeine based on various factors, such as age, medications, underlying health conditions, genetics, and how quickly their bodies metabolize it,” Marcus cautioned in a press release.

“What may be a reasonable amount for one person could cause unwanted effects, such as heart palpitations, anxiety, or sleep disruption, in another. That’s why it’s important to pay attention to how your body responds to caffeine and talk with your healthcare team about what is right for you,” Marcus added.

His group suggested that harm was more likely when coffee and caffeinated products were combined with sugar, flavored syrups, and dairy products. High caffeine doses, such as those in energy drinks, should be avoided.

Marcus and colleagues acknowledged that their review included reports with various study designs and limitations. A healthy user bias was possible in studies with participants with a prior history of consuming caffeine, for example.

Priorities for future research include more randomized studies such as crossover and pragmatic trials, they suggested. Researchers should also try to disentangle caffeine from other components of coffee and other beverages like polyphenols, assess individual differences in response, and examine dose-response and thresholds in individuals with hypertension and other cardiovascular diseases.

Moreover, it remains unknown whether caffeine abstainers might benefit from initiating regular coffee consumption, the committee noted.