The current studies find that higher levels of chocolate consumption are associated with a reduced risk for any cardiovascular disease and of stroke in particular. These findings may change physician advice to patients regarding diet.
Cocoa has been consumed in one form or another for thousands of years, but the modern incarnation of chocolate has been demonized as a possibly addictive food that leads to obesity and poor health outcomes.
However, those who would dismiss chocolate as completely unhealthy should consider some of its basic properties.
Cocoa contains flavonoids, which have antioxidant properties. It also contains high amounts of stearic acid, a saturated fatty acid that does not promote hypercholesterolemia to the same degree as other fats.
Chocolate has proven metabolic effects that suggest a potential for reducing the risk for cardiovascular disease.
In a randomized trial, consumption of solid dark chocolate and liquid cocoa improved endothelial function and blood pressure compared with placebo.
One caveat of this research is that sugar-free cocoa improved these outcomes to a greater extent than regular cocoa.
In another trial, consumption of cocoa improved intravascular concentrations of nitric oxide as well as endothelial function in a small cohort of smokers.
Reductions in blood pressure may help to explain why chocolate consumption may improve cardiovascular health.
Large population-based studies have found significant differences in blood pressure based on chocolate consumption, with reductions of 1 to 3 mm Hg in systolic and diastolic blood pressure when comparing groups who consumed the most vs the least chocolate.
In addition, a meta-analysis of 13 randomized studies found that consumption of dark chocolate and cocoa acutely reduced mean systolic and diastolic blood pressure values by -3.2 and -2.0 mm Hg, respectively, compared with placebo.
However, in subgroup analyses, the effect on blood pressure was significant among adults with elevated blood pressure but not among normal adults.
Chocolate may also help metabolic outcomes, or at least not promote harm.
A meta-analysis of short-term trials of dark chocolate and cocoa found that chocolate reduced total cholesterol (mean reduction, -6.23 mg/dL) and low-density lipoprotein (LDL) cholesterol (-5.90 mg/dL), while having no significant effect on high-density lipoprotein cholesterol or triglycerides.
A significant trend toward a lower risk for incident diabetes among Japanese men who ate more chocolate snacks was also noted, although this trend did not reach statistical significance among women.
These findings are promising but less important if chocolate cannot protect against more severe clinical outcomes, such as myocardial infarction and stroke.
There has been research into this subject involving over 100,000 total participants, and the systematic review and meta-analysis by Buitrago-Lopez addresses the collective outcomes of these studies.
Researchers used multiple medical databases to find studies of chocolate consumption with outcomes related to cardiovascular disease. Studies published up to October 2010 were eligible for review. Of 4576 references originally identified, 53 articles were fully reviewed by 2 investigators. A total of 7 studies were included in the meta-analysis.
The collective research included a total of 114,009 participants. Participants’ ages ranged from 25 to 93 years. Most studies were conducted in Europe and North America.
Chocolate consumption was measured by using food frequency questionnaires in 6 studies; the remaining study used food diaries. Little differentiation between types of chocolate was done in the studies, and they generally used the frequency of any chocolate consumption as the primary study variable.
Study outcomes included myocardial infarction, diabetes, cardiovascular disease, coronary heart disease, heart failure, and stroke.
The main study outcomes were adjusted in all studies to account for age, sex, body mass index, physical activity, smoking, education, and other dietary factors (including coffee consumption). Some of the studies also adjusted their outcomes to account for medication use.
Five of the 7 studies reported a significant inverse association between chocolate consumption and risk for heart disease and diabetes.
In comparing the highest with the lowest levels of chocolate consumption, the relative risk for cardiovascular disease was 0.63. The respective relative risk for stroke specifically was 0.71.
(1.00 is normal. Less than 1.00 is good)
Chocolate consumption was found not to be significantly associated with risk for incident heart failure in 2 studies.
Data were insufficient to draw conclusions regarding the relationship between chocolate consumption and the risk for incident type 2 diabetes.
Moreover, chocolate is not the only food that contains flavonoids. Soy products and tea are also rich in flavonoids.
A review of randomized trials found that consumption of soy protein can significantly reduce diastolic blood pressure and LDL cholesterol values.
Although consuming black tea raised blood pressure temporarily, regularly drinking green tea reduced LDL cholesterol levels.
It is worth noting that chocolate had more profound effects in lowering blood pressure than did soy protein and tea in this study.
Cocoa is prepared in myriad ways, and physicians should also consider that most clinical trials focus on the use of cocoa and dark chocolate with the highest concentrations of flavonoids.
But this form of chocolate is less popular among consumers, who prefer lighter chocolate.
Patients considering the potential health benefits of chocolate need to understand this point, as underlined in a study comparing dark chocolate rich in flavonoids with white chocolate, which is practically devoid of flavonoids.
Researchers found that dark chocolate significantly improved coronary blood flow as measured by Doppler echocardiography. In contrast, white chocolate had no effect on coronary flow.
The degree to which any cardiovascular benefit of chocolate is diluted by the sugar and fat added to the final product remains a substantial unknown. However, the effect of sweets in the current obesity epidemic may well be overstated.
A recent study of national data from the United States found that although adults who ate more chocolate and sugar-containing candy consumed more total calories, saturated fats, and added sugars, they had lower body mass index values, mean waist circumference, and serum C-reactive protein values than did nonconsumers.
Candy and chocolate were also associated with some improvements in blood pressure and metabolic parameters.
Man does not live on bread alone. Nor does he live solely on steamed vegetables. Patients will always snack and have their dietary guilty pleasures. But now physicians can help these individuals make healthier choices among the items they crave but may be afraid to eat or drink.
A glass of wine with dinner? That could benefit your cardiovascular health.
That extra cup of coffee in the morning? It might help to prevent diabetes.
And now we can consider adding flavonoid-rich dark chocolate and cocoa — in moderation — to that list of treats.
• Consumption of dark chocolate and cocoa seems to improve endothelial function and blood pressure.
• The current meta-analysis demonstrates a link between chocolate intake and reductions in cardiovascular disease generally and stroke specifically.
• Chocolate consumption did not seem to be related to the risk for heart failure.
• Chocolate comes in many forms, most of which contain substantial amounts of sugar and fat.
Dr. Pinna says:
I think we are going to see more and more articles like this one. Scientific investigators are always searching for new areas of research. Their careers depend on the number of publications under their name. The chocolate industry has some major players. We know that Cadbury, Hershey’s, Lindt, Ghirardelli, Kraft Foods etc., etc., are big names. However, there are hundreds of smaller players. Most likely the Chocolate manufacturer’s association will support such studies.
If history is a good example, the pharmaceutical companies will also jump in, find the exact molecule that produces the best effects and sell that as a pill.
You do not have to wait. Just buy dark bitter chocolate and eat some daily. I do.