Coffee lovers have a fresh green light from heart experts—up to a point. A scientific statement from the American Heart Association on Monday says most adults can safely consume as much as 400 milligrams of caffeine a day—about five 8-ounce cups of caffeinated coffee—without increasing their risk of heart disease. They may even see some protection against conditions like stroke, heart attack, atrial fibrillation, and type 2 diabetes, Gizmodo reports. "Habitual moderate coffee consumption can be part of a healthy lifestyle," the authors write in the journal Circulation, though they note the relationship between caffeine and cardiovascular health is complicated and still being studied.
The warning flag is waved not at coffee but at high-octane sources like energy drinks and shots, which can push intake beyond that 400mg mark and have been tied to dangerous heart rhythm issues, high blood pressure, and, in rare cases, deaths. Unfiltered coffee may also raise LDL ("bad") cholesterol via a compound called cafestol. Genetics have a say, too, per ABC News. Variations in a liver enzyme gene, CYP1A2, determine how quickly a body metabolizes stimulants. Some people ingesting less than 400mg of caffeine can face sleep disruption or blood pressure spikes. The upshot, per Gregory Marcus, lead author of the statement: For most people who stick to moderate coffee or tea, caffeine isn't a heart threat—but those pounding energy drinks should think twice.
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