The cup of coffee you drink to get you through your afternoon slump at the office may be doing you more good than you realize. Moderate coffee consumption appears to reduce the risk of developing clogged, calcified, arteries that can cause atherosclerosis and cardiac events.

Scientists had been concerned that drinking coffee could lead to a higher risk of cardiovascular disease because it has been associated with an increase in blood pressure and cholesterol levels in the blood. The findings of this new Korean study offer evidence, however, that drinking coffee has beneficial effects on cardiovascular health by keeping arteries clearer.

Regular, moderate coffee consumption may reduce the risk of developing type 2 diabetes, a strong risk factor for atherosclerosis, and may improve insulin sensitivity and beta-cell function.

The scientists looked at the association between coffee consumption and coronary artery calcium (CAC), which is a precursor to atherosclerosis, a hardening of the arteries that can lead to blood clots which could cause a heart attack or stroke.

Over 25,000 men and women with no detectable coronary artery disease were enrolled in the study. The average age of the study participants was 41. Each underwent a screening exam and filled out a food questionnaire, and was given a cardiac computed tomography (CAT) scan to determine their CAC.

The researchers looked for an association between the amount of coffee consumed per day and how much CAC an individual had. For the purposes of their study, the scientists categorized coffee consumption as none, less than one cup per day, one to less than three cups per day, three to less than five cups per day, or at least five or more cups per day.

On average, the study participants drank 1.87 cups of coffee per day. The prevalence of CAC among study participants was 13.4 percent.

Coronary artery calcium went down as coffee consumption went up — up to a point. CAC dropped for those who reported they drank between one and less than three cups per day and dropped even more for those who drank at least three and less than five cups per day.

It was a different story, however, among those coffee fiends who drank at least five or more cups per day: their CAC rose. This association was similar when the researchers divided the subjects into subgroups based on age, sex, weight, smoking status, and also on obesity, hypertension, and hypercholesterolemia status.

The authors offered a few theories for this U-shaped association: regular, moderate coffee consumption may reduce the risk of developing type 2 diabetes, a strong risk factor for atherosclerosis, and may improve insulin sensitivity and beta-cell function. An earlier analysis of data from 36 studies had found that coffee reduces the risk of type 2 diabetes and improves insulin sensitivity.

The study is published in the journal Heart.