The study did not include people with known heart disease, so it is not clear if drinking coffee or tea is beneficial for them, study researcher Yvonne T. van der Schouw, PhD, tells WebMD.
"But for healthy people, it appears that drinking coffee and tea is not harmful and it may even offer some benefits," she says.
Several earlier studies have also found that drinking coffee or tea lowers the risk for heart disease.
In one, reported in 2008, women who drank four to five cups of coffee a day had a 34% lower risk of dying from heart disease while men who drank more than five cups had a 44% lower risk.
In another study published the same year, drinking green tea was associated with improved blood vessel function and lower heart disease risk.
But most of the people in The Netherlands study drank black tea, which is also consumed more than green tea in America.
The study appears in the latest issue of the American Heart Association journal Arteriosclerosis, Thrombosis and Vascular Biology.
"The perception has been that green tea is the 'healthy' tea, but this study suggests black tea may be just a good for the heart," University of Vermont professor of nutrition Rachel K. Johnson, PhD, tells WebMD. "That will be good news to people like me who are not big green-tea lovers."
Flavonoids in Tea, Coffee May Protect Heart
While six cups of tea may sound like a lot, Johnson points out that a large glass of iced tea may contain two to three cups of liquid.
"Iced tea is very popular in some parts of the country, especially in the summer," says Johnson, who is also a spokeswoman for the American Heart Association. "Just make sure to go easy on the sugar. I would hate for people to get the message that they should be drinking more sugar-sweetened beverages."
The researchers suggest that powerful antioxidants called flavonoids found in black and green tea and coffee may explain the protective effect seen in the study.
Other foods that contain flavonoids include red wine, red grapes, dark chocolate, blueberries, and red beans.