Two new studies show that as little as one cup of coffee can cause a temporary increase in the stiffening of arterial walls. Researchers at Athens Medical School in Greece looked at the effects of caffeine on a group of people with normal blood pressure, and a group that had mild hypertension, or elevated blood pressure.

In findings released last week, the researchers also said that the equivalent of two or three cups of coffee temporarily raised blood pressure in the group with hypertension and increased stiffness in the aorta—the main artery leaving the heart.

Chief researcher Dr. Charalambos Vlachopoulos said that while further research is needed to understand the long-term effects of this arterial stiffening, this extra load on the heart is something that people with high blood pressure may wish to avoid.

DeWitt Williams, health ministries director for the Seventh-day Adventist Church in North America, says he is not surprised by the studies’ findings.

The pervasive use of coffee in today’s society has lulled many people into thinking that caffeine is harmless, he says. But he points to a litany of adverse health problems that have long been associated with caffeine use, including: increases in the rate of irregular heartbeats; decreased blood flow to the liver; increases in cholesterol; and interference with the absorption of important minerals, such as iron. One milligram of calcium is lost for every 10 milligrams of caffeine consumed, he says, and one cup of strong coffee has 103 milligrams of caffeine.

“Coffee may perk you up in the short term, but in the long run it lets you down,” says Williams. “Not only is it associated with heart problems, but it has also been linked to bladder cancer. Those who drink two cups of coffee a day double their risk of bladder cancer versus those who don’t drink any at all.”

For more than 100 years the Adventist Church has recommended that people avoid caffeine and other non-medicinal drugs as part of a healthy, balanced lifestyle that includes good nutrition and exercise, as well as attention to the social and spiritual aspects of life.