Health

Coffee refill? Go for it, says American Heart Association, with note of caution.

Co-author of new guidance explains how many cups a day are safe — possibly even good for you — and why energy drinks are different

Anna Lamb

Harvard Staff Writer

July 29, 2026

3 min read

Good news for java enthusiasts: Earlier this month the American Heart Association released a statement endorsing up to five cups of caffeinated coffee a day as safe for the average adult. In fact, the statement adds, drinking more coffee may be good for you.

“I don’t think we are there yet in terms of recommending people who don’t drink coffee initiate coffee-drinking as a preventive strategy,” said Frank Hu, the Fredrick J. Stare Professor of Nutrition and Epidemiology at Harvard’s T.H. Chan School of Public Health. Hu is a co-author of the statement.

“For people who are already drinking coffee, I think the data is very reassuring that two to five cups per day is not just safe, it may be healthful in terms of lower risk of certain chronic diseases.”

Using large cohort data from studies like the Nurses’ Health Study and Health Professionals Follow-Up Study, AHA researchers looked at behavior over decades and found no long-term negative impacts on blood pressure and heart rhythms associated with the overconsumption of caffeine in the participants who limited their coffee intake to the two-to-five-cup range.

Frank Hu. Harvard file photo.

And, according to the statement, drinking up to five eight-ounce cups of caffeinated coffee was linked to a lower risk of developing Type 2 diabetes, heart disease, heart failure, and stroke. There are a few hypotheses behind these benefits, Hu said, but ultimately more research is needed to determine the exact mechanisms at work.

“Coffee contains not just caffeine, but numerous bioactive compounds like polyphenols, which may have health benefits,” Hu said. “Studies have shown that the metabolism of the polyphenols by the gut bacteria leads to production of beneficial metabolites, the small-molecule chemical compounds produced by the bacteria, which can reduce oxidative stress and reduce chronic inflammation, and may even have beneficial effects on insulin sensitivity.”

“Coffee contains not just caffeine, but numerous bioactive compounds like polyphenols, which may have health benefits.”Frank Hu

Coffee, Hu said, also contains high amounts of chlorogenic acid, which is a chemical compound that has been shown to reduce glucose absorption and improve glucose metabolism. These compounds, he said, have been found in both regular coffee and decaffeinated blends.

Where those benefits are not seen is in energy drinks — another popular source of caffeine for many. These, Hu said, should not be lumped into the AHA sanction.

“Energy drinks typically contain much higher amounts of caffeine and also a very high amount of added sugar and taurine and other stimulants, and so the potential harms come not just from high-dose caffeine, but also other components,” Hu said. “And also those kinds of drinks do not contain the potentially beneficial biaxial compounds like polyphenols.”

For otherwise healthy adults, the AHA suggests consuming no more than a maximum of 400 milligrams of caffeine a day. Bang Energy contains 300 milligrams in a single 16-ounce serving, while other popular brands such as Celsius and Prime Energy contain 200 milligrams a pop.

The size of a drink, Hu said, is something to note even when selecting a healthful coffee.

“If you use the standard 12-ounce cup, it would be like three cups per day. Not like a big latte you get from Starbucks,” Hu said. “And we have found that if you add too much sugar and cream, you can dilute the health benefits of coffee. It’s almost like a common sense, but this is something I think we need to be mindful of.”