A study published in the journal Scientific Reports shows that consuming dark chocolate can significantly reduce the risk of essential hypertension. Essential hypertension refers to multifactorial high blood pressure with no clear cause.
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Cardiovascular diseases are the leading cause of disability and death worldwide and contribute significantly to the global burden of disease. In 2019, the estimated total number of cardiovascular disease cases was 523 million, 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 diseases, several studies have been conducted to identify both risk factors and prevention measures. Some small, randomized, controlled trials have shown that dark chocolate promotes cardiovascular health. The three main flavanols in dark chocolate, including procyanidin, catechin, and epicatechin, are known to have positive effects on the cardiovascular system.
In this study, scientists used Mendelian randomization to examine the causal relationship between the consumption of dark chocolate and the risk of cardiovascular diseases. Mendelian randomization uses measured variations in genes of known function to investigate the causal effect of a modifiable exposure on diseases in observational studies.
Scientists obtained summary data from a genome-wide association study on dark chocolate consumption from the MRC Integrative Epidemiology Unit (University of Bristol) website. The data included 64,945 participants of European descent. They identified 21 independent single nucleotide polymorphisms as genetic instrumental variables to predict dark chocolate consumption. An instrumental variable is a type of variable that should have no direct impact on the outcome.
Furthermore, scientists obtained summary data on cardiovascular diseases from various publicly available genome-wide association studies. They synchronized the datasets for dark chocolate consumption and cardiovascular diseases to align the direction of the alleles of the single nucleotide polymorphisms for both.
They then analyzed the data to determine the causal relationship between genetically predicted dark chocolate consumption and the risk of 12 cardiovascular diseases, including heart failure, coronary heart disease, myocardial infarction, atrial fibrillation, non-rheumatic valve disease, non-ischemic cardiomyopathy, essential hypertension, venous thromboembolism, deep vein thrombosis, stroke, ischemic stroke, and transient ischemic attack. They also conducted sensitivity analyses to assess the robustness of the Mendelian randomization analysis results.
The study results showed that dark chocolate consumption significantly lowers the risk of essential hypertension. A presumed negative association between dark chocolate consumption and the risk of venous thromboembolism was observed in the study. No significant association with dark chocolate consumption was observed for other tested cardiovascular diseases.
This study demonstrates that genetically predictable dark chocolate consumption is significantly associated with a lower risk of essential hypertension and presumably with a lower risk of venous thromboembolism.
Available evidence suggests that flavanols in dark chocolate improve endothelial function, promote vasodilation, and can prevent platelet aggregation by increasing nitric oxide release. Flavanols are also known for their strong antioxidant and anti-inflammatory effects. It is believed that all of these activities of flavanols are the main factors for a healthy cardiovascular system.
The hypertension data used in this study includes cases of secondary hypertension, which essentially reflects the manifestation of kidney disease, renal vascular disease, and some endocrine disorders of the cardiovascular system. However, the study does not investigate a causal relationship of these diseases with dark chocolate consumption. Therefore, the scientists advise not to rely solely on dark chocolate to prevent essential hypertension. Instead, people at high risk of essential hypertension can replace unhealthy snacks with dark chocolate to improve their cardiovascular health.
As mentioned by the scientists, this study used a small sample of exposure data. Additionally, the identified single nucleotide polymorphisms did not reach the conventional genome-wide significance threshold. However, these single nucleotide polymorphisms can be considered effective instrumental variables as their Fisher statistics values (a measure of the variance ratio) are greater than 10. A Fisher statistic value of over 2.5 is required to reject the null hypothesis. Furthermore, the results of sensitivity analyses showed the robustness of the estimated causal effects for almost all endpoints.
This study used data from summer populations of European descent, limiting the generalizability of the study results to other populations.
Overall, the study provides valuable information for the prevention of essential hypertension in the general population. Further clinical research is needed to definitively establish the causal relationship between dark chocolate consumption and the risk of cardiovascular diseases.