June 26, 2012 -- Drinking coffee in moderation may reduce your risk of heart failure as you age, according to a new analysis.
What's moderate? About two cups a day, if you're drinking the typical U.S. coffee serving, says researcher Murray Mittleman, MD, DrPH, director of cardiovascular epidemiology at Beth Israel Deaconess Medical Center.
"Beyond that, any potential benefits seem to decrease and eventually go away," Mittleman tells WebMD, while making clear that this study found a link, but not cause and effect.
About 5.8 million Americans have heart failure, according to the CDC. It occurs when the heart can't pump enough blood to the body.
"We are seeing great increases in the incidence of heart failure," says Mittleman, who is also associate professor of medicine and epidemiology at Harvard University.
Although heart failure can be controlled with medications and lifestyle changes, it greatly affects quality of life, Mittleman tells WebMD.
Mittleman's team analyzed the results of five previously published studies that looked at coffee intake and heart failure.
Four studies were done in Sweden. The fifth was done in Finland. Mittleman's research group was involved in three of the studies.
The people in the studies may have drank both caffeinated and decaf, Mittleman says. However, in Sweden and Finland, most coffee is caffeinated, he says.
In all, the researchers found more than 6,500 heart failure reports in more than 140,000 people. The follow-up time varied from study to study. It ranged from about eight to 35 years.
The researchers looked at the coffee-drinking habits of all the men and women.
Those who drank three or four servings a day had the best protection from heart failure, Mittleman says. Drinking that amount, compared to not drinking, reduced heart failure risk by 11%.
However, Mittleman says, those four servings are European style and must be translated to typically larger U.S. serving sizes.
In the countries involved in the studies, he says, "a serving size might be like 4-5 ounces."
That is about half or less than what is served in popular U.S. coffee chains, Mittleman says. For instance, at one chain, a short is 8 ounces, a tall 12, and a grande is 16 ounces.
Three or four European servings would be equivalent to about two U.S. servings, or up to about two 10-ounce cups, he says.
As coffee intake increases, the benefit declines, Mittleman found. "When you get up to five or six U.S. servings a day, we seem to see there is no further benefit and perhaps you are getting into a territory with increased risk," he says.
"From these data, with respect to heart failure risk, stopping at about six [cups, U.S. style] would be wise," he says."Once you get beyond about 50 ounces a day, or five 10-ounce cups, you might be getting into harm territory."