Whether it’s first thing in the morning or at 3 p.m., a cup of coffee can perk you up—but it could also affect your heart health.
Your favorite cuppa may contribute to higher cholesterol levels, depending on how it’s brewed and filtered, according to recent research published in the journal Nutrition, Metabolism & Cardiovascular Diseases.
While the researchers specifically focused on the potential cholesterol-raising effects of coffee brewed by machines commonly found in Swedish—not U.S.—workplaces, the findings are a good reminder for people in all countries that “the processing, the brewing of the coffee, does make a difference” in how it affects health, said JoAnn Manson, MD, MPH, DrPH, chief of the Division of Preventive Medicine at Brigham and Women’s Hospital in Boston.
For decades, studies have shown a connection between coffee consumption and cholesterol levels. That link is apparently driven by compounds called diterpenes that are naturally found in coffee beans. Diterpenes seem to both raise levels of “bad” LDL cholesterol and slightly lower levels of “good” HDL cholesterol, according to prior research.
How coffee is brewed and then filtered, however, has a major impact on what ends up in your cup, research suggests.
Paper filters, like those used in classic drip-coffee machines, seem to remove most diterpenes from the finished brew, while unfiltered coffee (such as boiled coffee) and espresso tend to contain higher levels of these compounds. For that reason, the 2023 Nordic Nutrition Recommendations specifically warn against drinking lots of unfiltered coffee.
David Iggman, MD, PhD, senior author of the new study and an associate professor in clinical nutrition at Uppsala University in Sweden, wanted to see how coffee machines often used in Swedish workplaces compare to these other brewing methods. “Swedish people drink a lot of coffee, and also during working hours we drink a lot of coffee,” Iggman told Health.
Iggman and his fellow researchers analyzed concentrations of two diterpenes—cafestol and kahweol—in coffee made by 14 different machines in four Swedish workplaces.
Most of the workplace machines they tested were “brewing machines,” which typically make one cup of coffee at a time. But, unlike some single-serving brewers commonly found in the U.S., these machines don’t use pods of coffee; instead, they internally mix coffee and hot water and pass the finished beverage through a metal filter before dispensing it. (Imagine something a bit like a coffee vending machine.)
For comparison, the researchers also tested diterpene levels in espresso and regular coffee made by a variety of home-brewing methods, including boiling, French pressing, percolating, and using a classic drip-coffee machine with paper filters.
In keeping with previous research, the researchers found that boiled coffee contained the highest diterpene concentrations in the group by far, followed by espresso; paper-filtered coffee had the lowest levels.
Coffee made in workplace brewing machines, meanwhile, tended to have significantly higher diterpene concentrations compared to all home-brewing methods except boiling, the researchers found.
“They varied quite a lot, but most brewing machines do contain quite high concentrations of these substances,” Iggman said. “It’s not as bad as boiled coffee, but it’s somewhere in between” boiled and filtered coffee.
The study didn’t test how consuming diterpene-rich office coffee actually affects employees’ health, so it’s impossible to draw firm conclusions on that front. The research also had other limitations, including a small sample size and limited knowledge about exactly how the different machines prepared and filtered coffee.
But, using previous research findings on diterpenes and cholesterol as their guide, Iggman’s team estimated that the difference between drinking a cup of brewing-machine coffee versus paper-filtered coffee affects cholesterol as much as “having a little bit of cream in each cup,” rather than downing the drink black, he said.
Such a difference could feasibly add up over the course of an entire career. If someone replaced three cups of brewing-machine coffee with the same amount of filtered drip coffee every workday for 40 years, Iggman’s team estimated they could potentially reduce their risk of atherosclerotic cardiovascular disease by up to 36%. Again, though, that’s just an estimation; Iggman’s team did not monitor real people in their study.
In general, Manson said, people should cap their consumption of unfiltered coffee or espresso at one serving per day, especially if they have underlying risk factors for cardiovascular disease.
Caffeine lovers who want more than one cup per day should consider switching to filtered coffee for the rest of their daily dose. “Why take the risk of increasing LDL cholesterol when you can drink filtered coffee?” Manson asked.
The new study fits into a long-running debate about how coffee affects health. Older research raised concerns about health risks potentially associated with coffee consumption, including coronary artery disease. But in more recent years, as science has advanced, the pendulum has swung the other way.
Modern studies have linked coffee to a wide range of health benefits, from a lower risk of type 2 diabetes to a longer life. A 2020 review article in the New England Journal of Medicine concluded that “consumption of 3 to 5 standard cups of coffee daily has been consistently associated with a reduced risk of several chronic diseases,” including cardiovascular diseases.
On balance, Manson agreed, regular coffee consumption appears to be associated with better cardiometabolic health, despite the research on diterpenes and cholesterol.
“This should not dissuade people from drinking coffee by any means,” Manson said. “But [it should] maybe lead them to the filtered coffee rather than the unfiltered types of coffee.”
