Q&A: Safe levels of caffeine do not appear to harm cardiometabolic health

Caffeine, the most commonly consumed drug in the world, may have heart-healthy benefits when consumed below certain levels and may even help prevent diabetes, according to a new American Heart Association scientific statement.

As Healio previously reported, prior research has shown various health benefits related to coffee intake, including a link to less atrial fibrillation recurrence in those with AF; anti-inflammatory benefits; and reductions in LDL with certain coffee filters.

In light of the literature, the American Heart Association issued a scientific statement, published in Circulation, detailing the relationship between caffeine intake and cardiometabolic health as well as recommendations for maximum daily intake for healthy individuals.

Gregory M. Marcus, MD, MAS, chair of the statement writing committee, and colleagues wrote that up to 400 mg, or five 8 oz cups of coffee, per day, was safe for most healthy adults and consumption may lower risk for developing diabetes.

The statement delineates the relationship between caffeine intake and CV risk factors and CVDs including arrhythmias, coronary artery disease, heart failure and stroke as well as the pharmacologic mechanism by which caffeine interacts with the cardiometabolic system.

Healio spoke with Marcus, who is a cardiologist and Endowed Professor of Atrial Fibrillation Research in the division of cardiology at the University of California, San Francisco, about the impact of caffeine on heart health; whether the type of caffeine impacts this relationship; and whether there exists any patient population who should avoid caffeine intake.

Healio: What was the motivation to publish this statement?

Marcus: Rigorous research on the topic of caffeine and CVD has been growing recently, now with randomized trials among ambulatory populations consuming common caffeinated substances — not just relying on small, laboratory-based trials of pure caffeine, for example — and a formal statement summarizing research on the subject had not previously been produced.

Healio: What are some of the common concerns you hear from patients regarding their caffeine intake?

Marcus: Many of patients that I see in my arrhythmia clinic have been told to stop caffeine consumption even though they had not actually experienced any problems with it. Many are delighted to learn that it is reasonable to drink their caffeinated coffee, assuming they had not noticed adverse consequences of it.

Healio: By what mechanism does caffeine affect CV health?

Marcus: One of the reasons caffeine is interesting to study and yet hard to summarize is because it has protean effects. Caffeine does not act on the CV system via only one mechanism, and in fact can influence different CVDs in different ways. Caffeine can amplify the effects of the sympathetic nervous system, or adrenaline, it can dilate some blood vessels as well as parts of airways in the lungs, and it can have diuretic effects leading to loss of fluid and likely salt via more urination. While caffeine does not reduce the need for sleep, it can reduce the sensation of sleepiness by blocking a naturally occurring substances in our bodies called adenosine. As an example of how none of these effects are simple, we also know that high-dose adenosine administered for medical purposes can trigger atrial fibrillation, hence blocking adenosine receptors may be one way that caffeine might protect against this common heart rhythm disturbance.

Healio: Why might caffeine intake lower diabetes risk?

Marcus: The mechanisms by which caffeine might lower diabetes risk are unclear. Short randomized trials have failed to demonstrate acute effects on lowering blood glucose, suggesting that, if indeed the observational data that those who consume caffeinated coffee experience a lower risk for diabetes is true, it is likely due to more chronic effects. There is some evidence that caffeinated coffee in particular may have beneficial effects on the liver, which in turn may have favorable effects on glucose metabolism. We found in a randomized trial of days assigned to caffeinated coffee vs. avoidance among participants wearing Fitbits, participants took an average of 1,000 more steps per day when exposed to caffeinated coffee. Therefore, these observed beneficial effects related to diabetes might be because caffeine motivates people to be more physically active.

Healio: Does the form of caffeine intake matter with regard to its cardiovascular benefit (eg, coffee vs. energy drinks vs. espresso)?

Marcus: Head-to-head studies on different forms of caffeine are rare to nonexistent. The great majority of the research demonstrating potential beneficial effects seems to be when studying caffeinated coffee. It is therefore important to emphasize that, in general, it can be difficult to disambiguate effects that might be related to caffeine per se vs. other constituents in coffee. Data regarding energy drinks are quite scant, but what limited data that is available suggests these high-dose and synthetic caffeinated products may actually be harmful to the heart, particularly in increasing risks of potentially dangerous heart rhythm disturbances and HF.

Read the rest of the article on Healio here.