Coffee fuels early risers and night owls, and during coronavirus isolation many people are brewing their own drinks at home.

A recent study shows only one problem with that: If you use a French press, you aren’t filtering your coffee well enough.

» Study finds there is such a thing as too much coffee

"Our study provides strong and convincing evidence of a link between coffee brewing methods, heart attacks and longevity," study author Dag S. Thelle, a professor at the University of Gothenburg, Sweden, said in a press release. "Unfiltered coffee contains substances which increase blood cholesterol. Using a filter removes these and makes heart attacks and premature death less likely."

The research was published recently in the European Journal of Preventive Cardiology, a journal of the European Society of Cardiology.

» Drink a lot of coffee? You're more likely to live longer, study finds

Thelle discovered 30 years ago that drinking coffee was linked to “bad” LDL cholesterol to such an extent it was likely “to have detrimental consequences for heart health.” Experiments identified the bad substances in coffee and found they could be removed using a filter. A cup of unfiltered coffee contains about 30 times the concentration of the lipid-raising substances compared to filtered coffee.

“We wondered whether this effect on cholesterol would result in more heart attacks and death from heart disease,” Thelle said.

So, over the course of 20 years, Thelle conducted a study on on a representative sample of the Norwegian population: 508,747 healthy men and women ages 20 to 79.

Participants completed a questionnaire on the amount and type of coffee consumed.

During those 20 years, “46,341 participants died. Of those, 12,621 deaths were due to cardiovascular disease. Of the cardiovascular deaths, 6,202 were caused by a heart attack,” the press release states.

» Drinking more coffee may help your gut health, researchers find

The study found that drinking filtered coffee was safer than no coffee at all. Filtered coffee was linked with a 15% reduced risk of death from any cause during follow up.

“For death from cardiovascular disease, filtered brew was associated with a 12% decreased risk of death in men and a 20% lowered risk of death in women compared to no coffee. The lowest mortality was among consumers of 1 to 4 cups of filtered coffee per day,” the press release states.

The study also found that unfiltered coffee was worse than  filtered brew for death from any cause, death due to cardiovascular disease and deaths from heart attacks.

“Our analysis shows that this was partly because of the cholesterol-increasing effect of unfiltered coffee,” Thelle said.

» Best of Atlanta: This is the best coffee shop in metro Atlanta