The consumption of cocoa and dark chocolate is associated with a lower risk of CVD, and improvements in endothelial function may mediate this relationship. Less is known about the effects of cocoa/chocolate on the augmentation index (AI), a measure of vascular stiffness and vascular tone in the peripheral arterioles. We enrolled thirty middle-aged, overweight adults in a randomised, placebo-controlled, 4-week, cross-over study. During the active treatment (cocoa) period, the participants consumed 37 g/d of dark chocolate and a sugarfree cocoa beverage (total cocoa ¼ 22 g/d, total flavanols (TF) ¼ 814 mg/d). Colour-matched controls included a low-flavanol chocolate bar and a cocoa-free beverage with no added sugar (TF ¼ 3 mg/d). Treatments were matched for total fat, saturated fat, carbohydrates and protein. The cocoa treatment significantly increased the basal diameter and peak diameter of the brachial artery by 6 % (þ2 mm) and basal blood flow volume by 22 %. Substantial decreases in the AI, a measure of arterial stiffness, were observed in only women. Flow-mediated dilation and the reactive hyperaemia index remained unchanged. The consumption of cocoa had no effect on fasting blood measures, while the control treatment increased fasting insulin concentration and insulin resistance (P¼0·01). Fasting blood pressure (BP) remained unchanged, although the acute consumption of cocoa increased resting BP by 4 mmHg. In summary, the high-flavanol cocoa and dark chocolate treatment was associated with enhanced vasodilation in both conduit and resistance arteries and was accompanied by significant reductions in arterial stiffness in women.

Consumption of cocoa and dark chocolate has been shown to increase flow mediated dilation (FMD), but less is known about its effects on arterial compliance. We examined whether vascular effects could be sustained over 4 weeks. We enrolled 30 middle‐aged, overweight adults in a randomized, placebo‐controlled, crossover study. At baseline and end of each treatment, we measured brachial artery diameter and augmentation index (AI), a measure of arterial stiffness. During the active treatment, participants consumed 37 g/d dark chocolate and a sugar free cocoa beverage (CHOC) [total flavanols (TF) = 332mg/d] in place of a snack. Color‐matched controls included a low‐flavanol chocolate bar and a sugar‐free, non‐cocoa beverage (CONT) (TF = 0 mg/d). Treatments were roughly equivalent in total calories and fatty acid content. After CHOC treatment, artery diameter was significantly increased under resting conditions (+0.2 mm) and at the post‐deflation peak (+0.2 mm). CHOC significantly reduced AI (−1.0 ± 2.5 vs. 6.1 ± 2.5, CHOC vs. CONT, respectively). FMD and body weight did not differ across treatments. These results indicate that cocoa and dark chocolate increase arterial diameter, primarily through a reduction in vascular stiffness. Future work should examine dose‐response relationships to determine the threshold polyphenol intake to produce optimal vascular responses. Funded by: The Hershey Company

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