Arranz S, Valderas-Martinez P, Chiva-Blanch G, et al. Cardioprotective effects of cocoa: Clinical evidence from randomized clinical intervention trials in humans. Mol Nutr Food Res. 2013;57(6):936-947.

Epidemiological studies and some clinical studies have indicated that cocoa (Theobroma cacao) consumption is associated with reduced risk of cardiovascular disease (CVD). These effects are attributed to the polyphenolic content in cocoa (12-18% of dry weight), especially the flavonoids. This review evaluates the effects of cocoa consumption on various cardiovascular risk factors.

Cocoa contains numerous flavonoids, including the monomeric flavan-3-ol epicatechin (35% of total phenolic content) and the oligomeric and polymeric flavan-3-ols known as procyanidins (58% of total phenolic content). The bioavailability of these flavonoids depends on how these compounds are absorbed, metabolized, and eliminated. Both food components (protein, fat, polysaccharides from milk or other foods) and the gut physiology of individuals can also affect the bioavailability of cocoa flavonoids.

There is contradictory information about the effects of cocoa consumption on lipid profiles. Cocoa intake reduced serum low-density lipoprotein cholesterol (LDL-c) in hypertensive individuals, whereas dark chocolate intake had no effects on cholesterol in healthy subjects; however, other research showed that both healthy subjects and patients with high cholesterol had reduced LDL-c and increased high-density lipoprotein cholesterol (HDL-c) after 4 weeks of cocoa consumption. Chronic cocoa consumption also improved HDL-c levels and reduced oxidized LDL-c. Moreover, a meta-analysis indicated that 2-12 weeks of cocoa consumption improved LDL-c and total cholesterol (TC).

There is less information available about cocoa effects and diabetes, another CVD risk factor. In 3 clinical studies from the same investigators, it was found that 100 g/day (88 mg flavanols) of dark chocolate for 15 days increased insulin resistance in both healthy and hypertensive subjects with or without glucose tolerance. On the other hand, different investigators showed that they could not improve insulin sensitivity after 2 weeks of consumption of a cocoa drink (900 mg flavanols) in patients with hypertension. Moreover, obese and overweight subjects had increased insulin sensitivity from a high- flavanol cocoa diet compared to a low-flavanol cocoa diet. Research also showed that insulin sensitivity worked best in acute treatments (< 3 weeks).

Several studies have also indicated cocoa flavonoids inhibit platelet aggregation. In particular, procyanidin-rich cocoa lowered leukotrienes and increased levels of prostacyclin compared to low-procyanidin cocoa. Other similar studies found that cocoa products with high polyphenolic content (600-900 mg) were the most effective at inhibiting platelet aggregation compared to cocoa products with low polyphenolic content. Although the acute intake of polyphenolics appears to be effective, other studies that assessed chronic intake of flavonoid-rich diets did not reduce platelet aggregation.

Several clinical studies evaluating vascular system effects showed that dark chocolate consumption, but not white chocolate consumption, reduced blood pressure (BP) in healthy subjects and patients with hypertension, glucose-intolerant hypertension, or prehypertension or stage I hypertension. Even small amounts of polyphenolic-rich dark chocolate reduced BP and improved the formation of the vasodilator nitric oxide in patients with hypertension. Both solid dark chocolate and liquid cocoa improved endothelial function and BP in overweight individuals; however, some studies suggested that older individuals benefit less from cocoa products due to their elevated levels of the vasoconstriction protein endothelin 1.

Other studies examining antioxidant activity have indicated that the flavanol content of cocoa products are associated with increased plasma antioxidant activity, prevention of LDL oxidation, and reduction of oxidative stress markers. The consumption of cocoa products caused plasma antioxidant activity to peak at 1-2 hours and reduced LDL oxidation after 4-12 weeks in healthy subjects, as well as decreased several markers of oxidative stress in short-term studies; however, other researchers have indicated that oxidative biomarkers did not change in healthy subjects after 3 weeks of white or dark chocolate intake or 2 weeks with high-flavonoid or low-flavonoid chocolate.

Studies have also showed that consumption of cocoa polyphenolics reduces inflammatory markers associated with CVD. More specifically, studies have found reduced expression of several inflammatory cytokines after cocoa consumption. In contrast, other research indicated cocoa intake caused neutral effects or only reduced one of the inflammatory cytokine markers. Moreover, high-sensitivity C-reactive protein (hs-CRP), a well-established inflammatory biomarker, had an inverse linear effect with cocoa flavonoids. Several studies also indicated that adhesion molecules associated with inflammation were reduced after cocoa consumption, while other studies showed no effects, especially when consumed with milk.

Regarding scientifically supported health claims, the European Food Safety Authority (EFSA) has recently approved a health claim for cocoa and circulation based on 16 human intervention studies. EFSA concluded that a cause-and-effect relationship had been established between the consumption of 200 mg of cocoa flavanols daily and the maintenance of normal endothelium-dependent vasodilatation, and that this amount could be provided by 2.5 g of high-flavanol cocoa powder or 10 g of high-flavanol dark chocolate. EFSA did not approve claims regarding cocoa's effect on BP lowering or protection of lipids from oxidative damage.

Overall, this review suggests that the consumption of cocoa products, at various doses and treatment durations, reduced several risk factors associated with CVD; however, most studies assessed acute consumption of cocoa flavanols, and therefore, more studies are needed to evaluate the long-term effects of cocoa intake, as well as the potential cardiovascular effects of other cocoa phytochemicals.