Key study points:
Primer: There is increasing evidence supporting the cardioprotective effects of chocolate consumption. In fact, studies have suggested that consuming dark chocolate daily may reduce cardiovascular events by as much as 85 per 10,000 population over 10 years time. It is theorized that this health benefit may arise from the flavonoids contained in chocolate, which help decrease levels of reactive oxygen and nitrogen species and inhibit oxidation of low-density lipoprotein (LDL) cholesterol. Further, chocolate has been shown to reduce platelet activation and aggregation, thus decreasing thromboembolism formation. Finally, procyanidins in cocoa have been shown to modulate cytokine expression, this altering the immune response and reducing inflammation.
While several studies have confirmed an association between chocolate consumption and reduced stroke risk, research has largely focused on cocoa’s health effects on women. The authors of this study aimed to examine the association between chocolate consumption and stroke risk in men.
This [prospective] study: 37,103 Swedish men between 45 and 79 years old were studied. Baseline data, including diet and cardiovascular risk factors (e.g. weight. smoking history, alcohol consumption, aspirin use, history of myocardial infarction, etc.) were collected from each man via mail questionnaires. Each participant was followed until the date of the first stroke event, death, or December 31, 2008, whichever occurred first.
Baseline data revealed that men in the highest quartile of chocolate consumption were more likely to be younger, leaner, have a university education, abstain from smoking, use aspirin, and consume more alcohol, red meat, and fruits and vegetables compared to the men with the lowest chocolate intake. Of the 37,103 men, there were 1.995 cases of stroke. Men in the highest quartile of chocolate consumption had a 17% lower risk of stroke, even after adjusting for age and other risk factors for stroke. Finally, a meta-analysis conducted by the authors using data from the study and from articles found on a review of two publication databases demonstrated a relative risk of stroke of 0.81 (CI: 0.73-0.99) for people in highest versus lowest levels of chocolate intake.
In sum: The authors of this study conclude that the “high consumption of chocolate is associated with a significant reduced risk of stroke”, with a 17% risk reduction demonstrated by their prospective cohort study and a 19% risk reduction demonstrated in their meta-analysis. These findings are consistent with studies that have previously established the efficacy of chocolate in stroke prevention in women and they provide a clinical correlation to research demonstrating cardioprotective anti-oxidant, anti-clot, and anti-inflammatory benefits of flavonoids. The authors note that the strength of this study comes from its large study population and near-complete follow up. However, they also note several limitations. First, chocolate consumption was calculated from self-reported values and measurements were only taken at one time point (baseline), thus reducing the study validity. Second, the type of chocolate consumed was not assessed. Given that previous studies have suggested reduced health benefit of milk chocolate when compared to dark chocolate and that the majority of chocolate consumed in Sweden is milk chocolate, these findings may have resulted from an unidentified confounder. Indeed, the authors admit that they “cannot exclude the possibility that unmeasured of residual confounding may have affected [their] results.”