Clinical Briefs
With Comments from Russell H. Greenfield, MD. Dr. Greenfield is Medical Director, Carolinas Integrative Health, Carolinas HealthCare System, Charlotte, NC, and Clinical Assistant Professor, School of Medicine, University of North Carolina, Chapel Hill, NC.
Short but "Sweet"Chocolate and CVD
Source: Hermann F, et al. Dark chocolate improves endothelial and platelet function. Heart 2006;92:119-120.
Goal: To determine whether the antioxidant actions of polyphenol-rich dark chocolate can improve endothelial and platelet function in smokers with known endothelial dysfunction and platelet hyperreactivity.
Design: Randomized, parallel group observational trial.
Subjects: Twenty-five male smokers.
Methods: The study was completed in two parts, both performed after subjects had fasted for at least 8 hours and had not smoked for at least 30 minutes. Five chronic smokers underwent a preliminary protocol after a 24-hour period free from exposure to polyphenol-rich foods. They were studied by high-resolution ultrasound of the brachial artery to determine flow-mediated dilatation (FMD) both before and after ingestion of 40 g of dark chocolate (74% cocoa). Endothelial function was then re-assessed at 2, 4, 8, and 24 hours. Twenty subjects were then randomized into two parallel groups, and endothelial and platelet function (shear stress dependent) were assessed at baseline (again following a 24-hour period of abstinence from polyphenol-rich foods) and 2 hours after ingestion of 40 g of dark or white chocolate.
Results: Positive results were found during the preliminary protocol involving the five subjects. In the second part of the study, dark chocolate significantly improved FMD compared with baseline, an effect that lasted 8 hours. White chocolate, however, had no effect on FMD. Similarly, no benefit could be ascribed to ingestion of white chocolate with respect to shear stress dependent platelet function, but benefits were seen with dark chocolate. Total antioxidant status significantly increased following dark chocolate ingestion.
Conclusion: Eating dark chocolate produces rapid improvement in endothelial and platelet function in otherwise healthy smokers 2-8 hours after ingestion.
Study strength: Manner in which FMD was determined.
Study weaknesses: Small sample size; lack of generalizability.
Of note: Women were excluded from the study because of known differences in vascular tone and reactivity induced by sex hormones; participants did not use dietary supplements or medications; immoderate ingestion of chocolate may have adverse effects on body weight and blood glucose and lipid levels (no changes in glucose or lipid levels were detected 2 hours after ingestion of chocolate); exposure to cigarette smoke induces endothelial dysfunction; glyceryl trinitrate-induced vasodilation was not affected by dark or white chocolate, suggesting a specific effect of dark chocolate on vascular endothelium.
We knew that: Polyphenols are a type of flavonoid compound possessing antioxidant activity and found in dark but not white chocolate; endothelial dysfunction and platelet activation can produce inflammation, thrombus formation, and vasoconstriction; smokers experience increased oxidative stress that enhances inactivation of endothelial derived nitric oxide, as well as oxidation of LDL cholesterol, both of which can promote cardiovascular disease; foods rich in polyphenols include green or black tea, berries, onions, apples, cabbage, cocoa products, and wine; high shear stress conditions occur at the site of significant stenosis or disrupted plaques; flavonoids may also alter 5-lipoxygenase activity and alter signal transduction pathways; dark chocolate possesses a higher polyphenol content per gram than wine, tea, or berries.
Clinical import: Smokers are at high risk of acute cardiovascular events due to increased atherogenic potential from a variety of causes, including induction of endothelial dysfunction. People who don't smoke, however, can also experience endothelial dysfunction. Although the results of this study are not readily generalizable, taken together with other data regarding the health benefits of dark chocolate (at least 70% cocoa), this study further promotes the idea that small daily servings of dark chocolate may offer significant health benefits.
What to do with this article: Keep a copy on your computer.
Greenfield RH. Short but sweetchocolate and CVD. Altern Med Alert 2006;9(2):24.Subscribe Now for Access
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