Interest in the links between coffee and health is not new. In 17th-century Europe, coffee was thought to aid digestion and gout but cause impotence and paralysis -- not a favorable trade-off, and also not correct. Today the coffee-health question focuses on the heart.
While some scientists have suggested that coffee might be bad for the heart, others (probably coffee drinkers) have repeatedly rebutted their findings. Among people who are not habitual coffee drinkers, the caffeine from two cups of coffee increases blood pressure by two to three mm Hg. This effect is short-lived and is usually absent among those who drink coffee regularly. Coffee can cause a temporary increase in heart rate, but it is an uncommon cause of abnormal heart rhythms. Boiled or unfiltered coffee contains oils that may increase total and LDL cholesterol levels, but these chemicals are removed by the filtering process, so most coffee has no effect on cholesterol. Finally, some studies suggest that coffee contributes to arterial stiffness. However, other research suggests that two cups of coffee per day actually causes arteries to relax.
In studying the health effects of coffee, cardiologists have focused on hypertension. Coffee does not cause high blood pressure. If you have high blood pressure and you like coffee, you can continue to drink it. Turning to the heart, large studies demonstrate no increased risk of coronary heart disease among coffee drinkers, whether they prefer regular coffee or decaf. While we have no prospective, randomized comparative studies examining cardiac outcomes over 10 to 20 years among people assigned to drink coffee or another beverage, there is enough evidence for us to conclude that coffee does not cause heart disease and that it can be part of a heart-healthy diet.
Recently scientists have raised concerns that coffee might be harmful to people with preexisting coronary heart disease. The question raised by scientific studies and media reports is whether coffee can trigger a heart attack in people with coronary heart disease. The answer is yes, but the risk appears to be extremely small and does not apply to all coffee drinkers. Among sedentary people who are not habitual coffee drinkers and who have risk factors for heart disease, a morning cup of coffee may cause a very, very small increase in the risk of a heart attack. People with these characteristics may have exaggerated changes in blood pressure and nervous system activity after a cup of coffee, and these factors could cause disruption of a vulnerable plaque in a coronary artery. Additional research suggests that the link between coffee and heart attacks might be mediated in part by a person's genes. A Costa Rican study determined that people who are genetically programmed to be slow caffeine metabolizers have an increased risk of suffering a heart attack as a result of coffee. However, the overall the risk of coffee triggering a heart attack is so small that it is not worth worrying about it or attempting to identify people who might have a genetic susceptibility.
What about tea? It is difficult to compare coffee and tea because tea drinkers tend to have healthier diets and lifestyles when compared to coffee drinkers. So we can't really tell you which one is better. But like coffee, both black tea and green tea have been associated with reduced risk of developing coronary heart disease in observational studies. However, the potential cardiac benefits of tea require drinking five to six cups per day. What should you drink? The data suggest that neither coffee nor tea is bad for the heart and the possibility that both may confer cardiac benefits. Choose your drink based upon your taste preference. Avoid boiled or unfiltered coffee, which increases cholesterol. And if you must add a sweetener or cream, use low-calorie and low-fat varieties.