By Serena Gordon
Unfortunately, these findings don't mean you can eat chocolate with abandon.
"Chocolate contains several nutrients that may benefit the heart," said study author Dr. Chayakrit Krittanawong, from Baylor College of Medicine in Houston.
But, he noted, "This is an observational study, meaning we cannot conclude [a cause-and-effect] relationship that eating chocolate can prevent or reduce heart disease. However, we can see some scientific signals that eating chocolate is probably beneficial to the heart in certain circumstances."
Chocolate may help keep the heart humming by contributing to health of the blood vessels. It contains a number of beneficial nutrients like flavonoids that may lower inflammation and increase good (HDL) cholesterol, the researchers said.
The new review, published July 23 in the European Journal of Preventive Cardiology, included six studies with more than 336,000 people. Most were from the United States, almost 69,000 were from Sweden and 1,200 were from Australia.
The participants' health was followed an average of almost nine years. More than 14,000 developed heart disease and almost 4,700 had a heart attack.
The researchers noted that there were some limitations to the review. They weren't able to control for lifestyle factors, such as physical activity. And they didn't have specific data on the types of chocolate people ate.
That's important because the type of chocolate likely matters.
Cardiologist Dr. John Osborne, from State of the Heart Cardiology in Dallas, reviewed the findings and explained, "When you make milk chocolate, you end up with mostly fat and sugar with modest amounts of chocolate."
The beneficial nutrients come from the chocolate itself, which is why health experts typically recommend dark chocolate, which has fewer added ingredients than milk chocolate, he explained.
Another limitation to the review, Osborne said, is that the nutrition information came from the people in the study recalling what they'd eaten in the past. People can forget what they've eaten or may not want to tell researchers exactly what they've had.
"If you're going to use chocolate for its possible health benefits, don't have more than an ounce of dark chocolate a day. You can get similar nutrients from vegetables and fruits though," Osborne noted.
"The benefit from this review seemed to be pretty modest. A chocolate a day -- or every week -- is not necessarily going to keep the cardiologist away," he said.
Dr. Len Horovitz, from Lenox Hill Hospital in New York City, also looked over the review and agreed that while chocolate might have some benefits, "You want the right ingredients" -- not necessarily what you'd find in an average commercial milk chocolate bar.
And, he added, "You can't have as much as you want. You can have a little bit, maybe one small piece of chocolate a day, but you need to remember there are calories and sugar and fat, too."
If you're really looking to benefit your heart health, Horovitz said it would be better to exercise at least three to four times a week and try to maintain a healthy body weight.
"These are measures that are a lot more helpful than chocolate," he said.