A study published in the journal Scientific Reports shows that consuming dark chocolate can significantly reduce the risk of essential hypertension. Idiopathic hypertension refers to high blood pressure that is multifactorial and has no clear cause.
Study: Dark chocolate intake and cardiovascular disease: a Mendelian randomized study
Record
Cardiovascular diseases are the leading cause of disability and mortality worldwide and contribute significantly to the global burden of disease. The estimated total number of CVD cases was 523 million in 2019, with the Middle East and North Africa having the highest prevalence and Central Asia and Eastern Europe having the highest mortality.
Given the high morbidity and mortality associated with cardiovascular disease, several studies have been conducted to identify both risk factors and preventive measures. Some small-scale randomized controlled trials have shown that dark chocolate benefits cardiovascular health. The three main flavanols found in dark chocolate, including procyanidin, catechin and epicatechin, are known to have beneficial effects on the cardiovascular system.
In this study, scientists investigated the causal relationship between dark chocolate intake and cardiovascular disease risk using the Mendelian randomization method. Mendelian randomization uses measured variation in genes of known function to examine the causal effect of a modifiable exposure on disease in observational studies.
Study design
The scientists obtained summary genome-wide association study data on dark chocolate intake from the MRC Integrative Epidemiology Unit (University of Bristol) website. The data included 64,945 European participants. They identified 21 independent single nucleotide polymorphisms as genetic organ variables for predicting dark chocolate intake. An instrumental variable is a type of variable that is not assumed to have a direct effect on the outcome.
In addition, the scientists obtained summary data on cardiovascular disease from several publicly available genome-wide association studies. They matched the data sets for dark chocolate intake and cardiovascular disease to align the allelic direction of single nucleotide polymorphisms for both.
They then analyzed the data to determine the causal relationship between genetically predicted dark chocolate intake and the risks of 12 cardiovascular diseases, including heart failure, coronary heart disease, myocardial infarction, atrial fibrillation, non-rheumatic valvular disease, non-ischemic heart disease, hypertension , venous thromboembolism, deep vein thrombosis, stroke, ischemic stroke and transient ischemic attack. They also conducted sensitivity analyzes to assess the robustness of the results of the Mendelian randomization analysis.
Important observations
The study findings revealed that consumption of dark chocolate significantly reduces the risk of essential hypertension. A suggestive negative association between dark chocolate intake and risk of venous thromboembolism was observed in the study. No significant association with dark chocolate intake was observed for other cardiovascular diseases tested.
Importance of study
This study reveals that genetically predicted intake of dark chocolate is significantly associated with a lower risk of essential hypertension and suggestively associated with a lower risk of venous thromboembolism.
Available evidence shows that flavanols present in dark chocolates can improve endothelial function, promote vasodilation and prevent platelet aggregation by increasing the release of nitric oxide. Flavanols are also known to have strong antioxidant and anti-inflammatory effects. All these activities of flavanols are believed to be the main contributors to a healthy cardiovascular system.
The hypertension data used in this study include cases of secondary hypertension, which is essentially the manifestation of renal disease, renal vascular disease, and certain endocrine diseases in the cardiovascular system. However, the study does not investigate any causal relationship of these diseases to dark chocolate intake. Thus, scientists advise that people should not rely on dark chocolate alone to prevent essential hypertension. Conversely, people at high risk for essential hypertension can replace unhealthy snacks with dark chocolate to improve their cardiovascular health.
As the scientists reported, this study used a small sample size of the exposure data. The identified single nucleotide polymorphisms also failed to reach the conventional genome-wide significance threshold. However, these single nucleotide polymorphisms can be considered effective instrumental variables, as Fisher-statistic values (a measure of the ratio of variances) are greater than 10. A Fisher-statistic value greater than 2.5 is required to reject the null hypothesis. Furthermore, the findings of the sensitive analyzes indicated the robustness of the estimated causal effects for almost all outcomes.
Summer-level data from populations of European ancestry were used in this study. This limits the generalizability of the study findings to other populations.
Overall, the study provides valuable information for the prevention of essential hypertension in the general population. More clinical research is needed to firmly establish a causal relationship between dark chocolate intake and cardiovascular disease risk.
