Drinking one to two cups of coffee a day may lower the risk of heart failure, according to reviewers analyzing recent research.
When they looked at a handful of studies examining the link between java and heart health, they found that moderate coffee consumption might bestow positive effects, despite concerns about caffeine possibly hurting the heart.
"The American Heart Association published a guideline statement saying that coffee may be harmful and that it may increase the risk of heart failure," said lead author Elizabeth Mostofsky, a research fellow at Beth Israel Deaconess Medical Center in Boston.
"Since then, other studies have been done," she said. "We summarized the literature and found that across the studies, moderate coffee consumption may reduce a person's risk."
When Mostofsky and her colleagues analyzed the results of five studies published from 2001 to 2011 -- four conducted in Sweden and one in Finland -- they found that drinking the equivalent of about two 8-ounce cups of coffee may lower heart failure risk as much as 11 percent.
But moderation is key.
Heavy coffee drinking, defined in the review as drinking four to five cups a day, provides consumers with no extra protection and may even be dangerous.
The findings, published Tuesday in the journal Circulation: Heart Failure, did not provide a precise explanation for why coffee may help lower heart failure risk. Nor did they distinguish between caffeinated and decaffeinated coffee, although they pointed out that caffeine is in most of the coffee consumed in the places studied.
Some studies have shown that drinking coffee increases blood pressure. And high blood pressure, which affects 1 in 3 adults in the United States, is a major risk factor for heart failure, causing the heart muscle to weaken and potentially give out.
But the researchers explained that habitual coffee consumption might help people build up a tolerance of its effects, so that regular drinkers would no longer experience a spike in blood pressure.
"Chronic coffee use may actually blunt some of the effects," said Dr. Elizabeth Ross, a cardiologist and spokeswoman for the American Heart Association. (The association publishes the journal in which the review appeared, but Ross was not involved with its publication.)
Prior research has also suggested that coffee consumption might help lower risk the for Type 2 diabetes, which increases the likelihood of heart failure. A 2009 study in the Archives of Internal Medicine found that with each cup coffee that a person consumed daily, the risk for diabetes dropped 7 percent.
"There is a lot of research showing that coffee has antioxidant benefits. That's the main mechanism that people tend to focus on," said Mostofsky, suggesting a possible link between coffee and the decreased risk for diabetes. "But it requires further research."
"You get to the truth in small steps," Ross said. "This is really just a first step looking more directly at how caffeine affects the heart. I don't think it settles the issue."
She stressed that the results might be reassuring for people who consume moderate amounts of coffee. But the findings do not mean that individuals who don't now consume coffee should pick up the habit, she said, adding that coffee is not a "health drink."
"If you want to protect your heart, you need to eat well, not smoke and get exercise," Ross said. "Those are the main things you need to do."