The research, published in the European Journal of Preventive Cardiology, was based on a synthesis of six studies with a total of 336,289 participants who reported their chocolate consumption.
During a median follow-up of nearly nine years, 14,043 participants developed coronary artery disease and 4,667 had a heart attack.
It found that people who ate chocolate at least once a week had an 8% reduction in risk of coronary artery disease compared to those who consume chocolate less frequently.
“Our study suggests that chocolate helps keep the heart’s blood vessels healthy,” said study author Dr Chayakrit Krittanawong of Baylor College of Medicine, Houston, Texas.
“In the past, clinical studies have shown that chocolate is beneficial for both blood pressure and the lining of blood vessels,” he continued. “I wanted to see if it affects the blood vessels supplying the heart (the coronary arteries) or not. And if it does, is it beneficial or harmful?”
Chocolate’s ‘healthy nutrients’
Dr Krittanawong said chocolate’s benefits for heart health could be linked to the ‘healthy nutrients’ it contains.
“Chocolate contains heart healthy nutrients such as flavonoids, methylxanthines, polyphenols and stearic acid which may reduce inflammation and increase good cholesterol (high-density lipoprotein or HDL cholesterol),” he observed.
Flavanols - such as epicatechin, catechin and procyanidins - have been shown to reduce myocardial infarct size in one animal study and to reduce platelet aggregation and improve endothelial function in several randomised controlled trials of healthy individuals or people with CAD. Methylxanthines have been shown to have beneficial effects on cardiovascular function. It has been demonstrated that polyphenols facilitate nitric oxide synthesis. Meanwhile, stearic acid has also been shown to reduce mean platelet volume.
The study did not examine whether any particular type of chocolate is more beneficial and whether there is an ideal portion size.
“Chocolate appears promising for prevention of coronary artery disease, but more research is needed to pinpoint how much and what kind of chocolate could be recommended,” Dr Krittanawong said.
While an optimal intake has not been determined, he warned against over-consumption.
“Moderate amounts of chocolate seem to protect the coronary arteries but it’s likely that large quantities do not. The calories, sugar, milk, and fat in commercially available products need to be considered, particularly in diabetics and obese people.”
Association between chocolate consumption and risk of coronary artery disease: a systematic review and meta-analysis
European Journal of Preventive Cardiology
Authors: Chayakrit Krittanawong, Bharat Narasimhan, Zhen Wang, et al