It has just been published in the European Journal of Preventive Cardiology.
The researchers say that the filtering acts to take out the lipid-raising diterpenes compared to filtered coffee. These compounds can raise cholesterol and lead to health problems.
They found that a portion of unfiltered brewed coffee contains about 30 times the concentration of the diterpenes kahweol and cafestol.
And they explain the finding that there are benefits to drinking filtered coffee over abstaining by concluding: “The lower mortality associated with filtered coffee as compared with no coffee might arise from coffee being rich in antioxidants, including polyphenols.”
Filtered coffee uses hot water dripped through coffee grounds held in a filter paper or fine mesh. Espresso, and espresso-based drinks such as latte rely on steam being forced through the grounds without a filter. Turkish coffee typically boils the grounds in water and they are simply left untouched in the bottom of the cup by drinkers.
The research suggests that drinking one to four cups of coffee a day reduces the risk of death from cardiovascular disease by 20% for women and 12% for men
The study analysed the drinking habits of more than 500,000 people over 20 years to determine the impact on the body of drinking filtered, instant and decaffeinated coffee.