Cocoa components reduce cardiovascular risk
By David Dunaief, M.D.
Valentine’s Day is one of the wonderful things about winter. For many, it lifts the mood and spirit. A traditional gift is chocolate. But do the benefits of chocolate go beyond Valentine’s Day? The short answer is yes, which is good news for chocolate lovers. However, we are not talking about filled chocolates, but primarily dark chocolate and cocoa powder.
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 high blood pressure. This is ironic, since many chocolate boxes are shaped as hearts. Unfortunately, it is not necessarily the chocolates that come in these boxes that are beneficial.
Let’s look at the evidence.
Effect on heart failure
Heart failure is very difficult to reverse. Therefore, the best approach is prevention, and dark chocolate may be one weapon in this crusade. In the Swedish Mammography Cohort study, those women who consumed dark chocolate saw a reduction in heart failure (1). The results were on a dose-response curve, but only to a point. Those women who consumed two to three servings of dark chocolate a month had a 26 percent reduction in the risk of heart failure.
For the dark chocolate lovers, it gets even better. Women who consumed one to two servings per week had an even greater reduction of 32 percent. However, those who ate more than these amounts 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.
This study was a prospective (forward-looking) observational study that involved more than 30,000 women over a long duration, nine years. The authors comment that chocolate has a downside of too much fat and calories and, if eaten in large quantities, it may interfere with eating other beneficial foods, such as 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 (2). Again, the effects were based on a dose-response curve, but unlike the previous study, there was no increased risk beyond a certain modest frequency.
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.
The study did not mention dark or milk chocolate; however, this was another study that took place in Sweden. In Sweden, milk chocolate has substantially more cocoa solids, and thus flavonols, than that manufactured for the U.S. There were over 1,100 patients involved in this study, and none of them had a history of diabetes, which is important to emphasize.
I don’t know anyone who does not want to reduce the risk of stroke. We tell patients to avoid sodium in order to control blood pressure and reduce their risk. Initially, sodium reduction is a difficult thing to acclimate to — and one that people fear. However, it turns out that eating chocolate may reduce the risk of stroke, so this is something you can use to balance out the lifestyle changes.
In yet another study, the Cohort of Swedish Men, which involved over 37,000 men, there was an inverse relationship between chocolate consumption in men and the risk of stroke (3). 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, chocolate consumption study was observational, not the gold standard randomized controlled trial, like aspirin studies.
One of the most common maladies, especially in people over 50, is high blood pressure. So, whatever we can do to lower blood pressure levels is important, including decreasing sodium levels, exercising and even eating flavonoid-rich cocoa.
In a meta-analysis (a group of 20 RCTs), 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 (4). These studies involved healthy participants, who are sometimes the most difficult in whom to show a significant reduction, since their blood pressure is not high initially. One of the weaknesses of this meta-analysis is that the trials were short, between two and 18 weeks.
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 (5). 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, allergies to chocolate and diabetes. 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 that the chocolate be 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 are probably where you will see the most cardiovascular benefits. Happy Post-Valentine’s Day!
References: (1) Circ Heart Fail. 2010;3(5):612-616. (2) J Intern Med. 2009;266(3):248-257. (3) Neurology. 2012;79:1223-1229. (4) Cochrane Database Syst Rev. 2012:15;8:CD008893. (5) Circulation. 2007 Nov 20;116(21):2376-2382.
Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, visit www.medicalcompassmd.com or consult your personal physician.