A cup of joe per day might keep the doctor away, but half a dozen or more is pushing it. Even though there are tons of legitimate reasons to drink coffee for good health, a recent study published in The American Journal of Clinical Nutrition shows that drinking six or more cups a day increases a person’s risk for developing heart disease by as much as 22 percent.

In their research, the University of South Australia’s Ang Zhou and Elina Hyppönen looked for a link between heart disease and the caffeine-metabolizing gene CYP1A2. They did this by analyzing data on 347,077 coffee drinkers in the U.K. aged 37 through 73. Of the sample size, there were 8,368 documented incidents of heart disease.

While they didn’t find a link between the gene and heart disease, they did find that heavy coffee drinkers were at higher risk across the board; those who drank six cups of coffee or more per day were 22 percent more likely to develop the condition than people who drank just one or two.

The likely reason? High levels of caffeine can result in high blood pressure, which is a leading cause of heart disease. The average cup of coffee contains 95 milligrams of caffeine. Six would have around 570.

“An estimated 3 billion cups of coffee are enjoyed every day around the world,” Hyppönen said in a statement. “Knowing the limits of what’s good for you and what’s not is imperative. As with many things, it’s all about moderation; overindulge and your health will pay for it.”

According to the American Heart Association, heart disease describes a number of conditions, many of which are related to atherosclerosis, a condition in which plaque builds up in the walls of the arteries. This increases the risk of forming blood clots, which could block blood flow completely and cause a heart attack or stroke. Heart disease (also known as cardiovascular disease) is the No. 1 cause of death globally, and an excess amount of coffee isn’t even the worst thing you can do for your heart.