The health benefits of chocolate are derived in large part from its flavonoid content — compounds that are produced by plants. These health benefits are seen in cardiovascular disease, including stroke, heart disease and blood pressure.
Effect on heart failure
In the Swedish Mammography Cohort study of 30,000 women, those who consumed dark chocolate saw a reduction in heart failure. Women who consumed two to three servings a month had a 26 percent reduction in the risk of heart failure, and those who consumed one to two servings per week had an even greater reduction of 32 percent.
However, those who ate more actually lost the benefit in heart failure reduction and may have increased risk. With a serving (1 ounce) a day, there was actually a 23 percent increased risk.
The authors note that chocolate has a downside of too much fat and calories and, if eaten in large quantities, it may interfere with eating fruits and vegetables.
The positive effects are most likely from the flavonols, a subset of flavonoids, which come from the cocoa solids — the chocolate minus the cocoa butter.
Impact on mortality from heart attacks
In a two-year observational study, results showed that chocolate seemed to reduce the risk of cardiac death after a first heart attack. Those who consumed chocolate up to once a week saw a 44 percent reduction in risk of death, and those who ate the most chocolate — two or more times per week — saw the most effect, with 66 percent reduced risk.
And finally, even those who consumed one serving of chocolate less than once per month saw a 27 percent reduction in death, compared to those who consumed no chocolate.
In yet another study, the Cohort of Swedish Men, with over 37,000 participants, those who ate at least two servings of chocolate a week benefited the most with a 17 percent reduction in both major types of stroke — ischemic and hemorrhagic — compared to those who consumed the least amount of chocolate.
Although the reduction does not sound tremendous, compare this to aspirin, which reduces stroke risk by 20 percent. However, the chocolate consumption study was observational, not a randomized controlled trial, like aspirin studies.
One of the most common maladies is high blood pressure. In a meta-analysis of 20 randomized control trials involving healthy participants, flavonoid-rich cocoa reduced both systolic (top number) and diastolic (bottom number) blood pressure significantly: -2.77 mm Hg and -2.20 mm Hg, respectively.
Why chocolate has an effect
Chocolate has compounds called flavonoids. The darker the chocolate, the more flavonoids there are. These flavonoids have potential antioxidant, antiplatelet and anti-inflammatory effects.
In a small, randomized controlled trial comparing 22 heart transplant patients, those who received dark flavonoid-rich chocolate, compared to a cocoa-free control group, had greater vasodilation (enlargement) of coronary arteries two hours after consumption.
There was also a decrease in the aggregation, or adhesion, of platelets, one of the primary substances in forming clots. The authors concluded that dark chocolate may also cause a reduction in oxidative stress.
It’s great that chocolate, mainly dark, and cocoa powder have such substantial effects in cardiovascular disease. However, certain patients should avoid chocolate such as those with reflux disease, diabetes and allergies to chocolate.
Be aware that Dutch-processed, or alkalized, cocoa powder may have lower flavonoid levels and is best avoided. Also, the darker the chocolate is, the higher the flavonoid levels. I suggest you aim for at least 60 to 70 percent dark.
Moderation is the key, for all chocolate contains a lot of calories and fat. Based on the studies, two servings a week is probably where you will see the most cardiovascular benefits.