Heart group says moderate coffee is safe, warns on energy drinks

The American Heart Association says most adults can consume up to 400 milligrams of caffeine a day without raising cardiovascular risk. The group’s new scientific statement also warns that concentrated caffeine products, including energy drinks and shots, may increase blood pressure and the risk of irregular heart rhythms.

The statement, published in the AHA journal Circulation, reviewed recent research on caffeine and cardiovascular disease. The AHA said 400 milligrams is roughly equal to three to five 8-ounce cups of regular black caffeinated coffee, depending on the brew.

Gregory M. Marcus, chair of the statement’s volunteer writing group and a professor of medicine at the University of California, San Francisco School of Medicine, said the reviewed evidence supports moderate coffee intake for most adults. Marcus also said high-dose caffeine products, including energy drinks and shots, may harm the heart and should be avoided.

Coffee findings are mixed but mostly reassuring

The AHA said black caffeinated coffee without sugar, syrups, cream or other additions was associated in studies with lower risks of Type 2 diabetes, heart disease, stroke, heart failure and some abnormal heart rhythms. The statement said drinking two to four cups of caffeinated coffee a day was linked with lower risks of heart disease, heart failure and stroke.

The group cautioned that much of the evidence is observational, meaning the studies can show associations but cannot prove cause and effect. The AHA also said coffee contains many compounds besides caffeine, including substances with antioxidant and anti-inflammatory properties, making it difficult to isolate caffeine’s role.

The review found that coffee’s effects may vary by condition and dose. According to the AHA, consuming more than four cups of caffeinated coffee a day may increase heart failure risk, while randomized trials have linked caffeine from coffee with a lower risk of atrial fibrillation but a higher risk of premature ventricular contractions.

Energy drinks carry a different risk profile

The AHA said caffeine should not be treated the same across all products. Energy shots may contain 40 to 69 milligrams of caffeine per fluid ounce, or about three to four times the concentration of regular caffeinated coffee, according to the statement.

The review said caffeine levels often found in energy drinks and shots were associated with high blood pressure and abnormal heart rhythms. The AHA said those risks have been reported even among people usually considered at low cardiovascular risk, including healthy adults younger than 30.

The statement said energy drinks, caffeine bars, gels and supplements may also include ingredients that speed caffeine absorption. According to the AHA, faster absorption could intensify caffeine’s effects, increase blood pressure and raise the chance of cardiovascular harm.

Individual responses vary

The AHA said caffeine usually reaches its highest concentration in the body about an hour after coffee is consumed, but timing and effects differ by genetics, metabolism, age and prior caffeine use. The statement said caffeine can temporarily raise blood pressure, heart rate, blood sugar and alertness, and may cause palpitations or sleep disruption in some people.

The group said additions to coffee, including sugar, flavored syrups, milk and cream, may weaken possible health benefits. It also noted that cafestol, a compound found in unfiltered coffee such as espresso, French press, Turkish coffee and boiled coffee, has been associated in randomized trials with higher LDL cholesterol.

The AHA called for more randomized controlled trials comparing caffeine from coffee with tea, soda, energy drinks, shots, foods and medications. Because evidence remains limited for energy drinks and newer caffeine products, the association said caffeine was not included in its 2026 Dietary Guidance to Improve Cardiovascular Health.

This story draws on original reporting from ScienceDaily.