Is Espresso Bad For You?

Are you familiar with the "coffee paradox?"

It goes like this: Coffee has a bunch of active ingredients. One of them, caffeine, is a stimulant - drink too much, and you'll put pressure on the cardiovascular system, which should lead to problems with the heart and circulation over time. Other ingredients in coffee, however, have antioxidant properties; they mop up toxins and reduce your risk of developing heart disease and diabetes.

That's why the balance of research has shown that moderate coffee consumption is probably good for the heart, despite the fact that it's rich in caffeine. That hasn't stopped people from hand-wringing over espresso - coffee's concentrated little brother, traditionally served strong and bitter in a little cup. It delivers more caffeine per ounce than a cup of americano, and that's led to investigations into whether it tips the balance of coffee's chemicals towards cardiovascular damage.

One study out of Italy that got a lot of press in 2015 could be read to say as much. Researchers looking at dilation response - the speed at which the brachial artery in the arm bounces back after blood flow is cut off - found 22% greater dilation after drinking decaf than after drinking espresso. Dilation response is one possible indicator of future cardiovascular problems.

The study was small - just twenty participants. It wasn't longitudinal, with data gathered from subjects repeatedly over a long period; instead, the dilation response was measured after a half-hour and an hour. It didn't look at what drinking different kinds of coffee does to the arteries over time, but measured their short-term effect on dilation.

This didn't stop sensational science columnists and headline-writers at a number of papers, including the Daily Mail and the Telegraph, from jumping on what they correctly saw as a highly-clickable opportunity for misinterpretation. "Single espresso a day can reduce blood flow to the heart," the Telegraph declared, saying "it confirms the high levels of caffeine found in a single espresso do have unfavourable cardiovascular effects" and reminding readers that a single 17-year-old girl was hospitalized after drinking too much espresso a decade ago and burying any scientifically responsible caveats and qualifiers in the graphs at the bottom of the page.

That's an alarmist take on a single small study bundled with a terrifying anecdote, but it's one of the first items that comes up if you ask Google whether espresso is bad for you. If you have a genetic history of cardiovascular disease, or if you're particularly sensitive to caffeine, there's good reason to talk to a medical professional about healthy levels of coffee consumption. Otherwise, the European Food Safety Authority says you can drink up to five espressos a day without hurting your heart.