ReviewCan chocolate consumption reduce cardio-cerebrovascular risk? A systematic review and meta-analysis
Graphical abstract
Introduction
According to the latest epidemiologic update, cardiovascular disease (CVD) is the most common cause of death in Europe (45% of all deaths) [1]. CVD is a heterogeneous and complex group of diseases, including cerebrovascular disease (stroke), myocardial infarction (MI), and coronary heart disease (CHD). The mortality rate is higher for women (49%) than for men (40%) for both stroke and CHD [2], [3]. A very high proportion (90%) of CVD is considered preventable [4] through a modification of lifestyle (moderate alcohol consumption, no smoking, physical activity, and healthy diet), blood pressure, and blood sugar control [5]. Some studies suggest that chocolate consumption might be inversely associated with prevalent calcified atherosclerotic plaques in the coronary arteries—a risk factor for CHD—as well as CHD incidence and mortality [6]. Chocolate is one of the most important dietary sources of flavonoids, polyphenolic compounds that may have cardioprotective effects due to hypothetical endothelial and platelet function [7] and important antioxidant action. Previous studies have shown that dietary intake of different types of flavonoids is associated with reduced risk for death from CHD and CVD [8]. Moreover, many flavonoids are potent antioxidants for low-density lipoprotein (LDL) oxidation, which is involved in the development of atherosclerotic diseases [9].
According to mythology, cocoa originated from the blood of an Aztec princess who preferred death rather than reveal the riches of her kingdom [10]. Mayas, Incas, and Aztecs cultivated the cocoa tree (Theobroma cacao) and praised it as “a gift of the gods.” Chocolate is produced from the seeds of the cocoa tree [11]. In ancient history, chocolate was seen an aphrodisiac accessible only to the affluent and the rich [12] and numerous positive properties to human health have been ascribed to it. In the 18th century, without scientific evidence, cocoa was believed to strengthen the heart and reduce angina pectoris [13].
Cocoa beans are now known to contain very high levels of flavonols that occur both as monomers of epicatechin and catechin and as polymerized flavonols, or procyanidins. These substances are responsible for many protective effects: They can reduce platelet aggregation and modulate redox-mediated vasodilation as well as the transcription of inflammatory cytokines [14].
Although many studies observe a statistically significant [13] or a nonsignificant [15] inverse association between chocolate consumption and total stroke, a moderate consumption of chocolate might be associated with a lower risk for heart failure (HF). This benefit may be due to favorable effects of cocoa products on blood pressure, which is a major risk factor for HF [16].
In patients free of diabetes surviving their first acute myocardial infarction (AMI), moderate chocolate consumption is associated with lower cardiac mortality, suggesting that individuals with CHD do not need to avoid chocolate [15].
The review by Corti et al. [7] focused on potential mechanisms involved in the response to cocoa and the potential clinical implications associated with its consumption. The beneficial effects of cocoa are most likely due to an increased bioavailability of nitric oxide (NO), which has an effect on the endothelium, such as vasodilation and prevention of leukocyte adhesion and migration. Reduced NO bioavailability is associated with endothelial dysfunction and eventually atherosclerotic disease [7]. The aim of this meta-analysis was to evaluate the association between chocolate intake and risk for CVD in the general population. In particular, we also assessed the risk of specific subgroups of CVD such as HF, stroke, AMI, and CHD.
Section snippets
Methods
A systematic review and meta-analysis in accordance with PRISMA guidelines was performed. The literature search was carried out on September 26, 2016, referring to PubMed, using predetermined keywords and a combination of Mesh terms, Title/Abstract, and text word. The search terms were selected based on three aspects: food intake, CVDs, and type of study; and finally, they were combined with Boolean operator AND/OR. The search terms related to the main aspects considered were:
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Food intake: Cacao∗
Results
We identified 396 potential articles and, after a preliminary screening of the title and abstract, 361 were excluded because they were reviews (n = 49), in a different language (n = 18), or not relevant (n = 294). Overall, 35 articles were eligible; however, 10 studies were further excluded because data were not available and another 9 because different outcomes were analyzed. The selection flowchart is shown in Figure 1. The detailed reasons for exclusion are presented in Table 1 [22], [23],
Discussion
The present meta-analysis showed that chocolate consumption was associated with a significant reduced risk for CVD (29%); in particular, 22% for AMI, 30% for stroke, 17% for HF, and 47% for CHD. Two studies further classified stroke as cerebral infarction and hemorrhagic stroke, but due to the low number of studies evaluating the differences between these two types of stroke, it was not possible to analyze the respective risk in this meta-analysis. Nevertheless, Larsson et al. [48], [49] found
Conclusion
Findings from the present analysis agree on a potential beneficial association of chocolate consumption with a lower risk for CVDs. These results do not exclude that overconsumption of chocolate/cocoa can have harmful effects. Further studies are required to confirm these data before any recommendations about chocolate intake can be made. In particular, it is important to focus attention on the different types of chocolate (milk or dark chocolate, and chocolate or cocoa in snacks). In fact,
Acknowledgments
The authors acknowledge Elisa Ascione and Christina Drace for the English revision.
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VG and TS contributed equally to the manuscript, and contributed to the conception and design of the study, data extraction, and analysis. DN contributed to the assembly and data interpretation. MV and MM contributed to the manuscript revision. All authors approved the final version of the manuscript.