Purpose: To assess the effects of the oral intake of flavonoid-rich dark chocolate on coronary circulation, we measured coronary flow velocity reserve (CFVR) by noninvasive transthoracic Doppler echocardiography (TTDE) in healthy adult subjects.
Materials and methods: The study was a randomized, single-blind design conducted for 2 weeks in 39 healthy men (mean age 29.7+/-3.9 years, range 23-40 years). Subjects were randomly assigned a daily intake of either flavonoid-rich dark chocolate (Meiji Black Chocolate 45 g, Meiji Seika kaisya Ltd, including cacao polyphenol 550 mg/day, 200 kcal) or non-flavonoid white chocolate (Meiji White Chocolate 35 g, Meiji Seika kaisya Ltd, including cacao polyphenol 0 mg/day, 140 kcal) as a control. CFVR was recorded by TTDE, and assessed before and after 2 weeks of intake. At the same time, we also assessed serum asymmetric dimethylarginine, 8-isoprostanes, and malondialdehyde-modified low-density lipoprotein (MDA-LDL) as markers of oxidative stress.
Results: Flavonoid-rich dark chocolate consumption significantly improved CFVR (3.38+/-0.49 before intake, 4.28+/-0.85 after intake; p<0.01), whereas non-flavonoid white chocolate consumption did not (3.28+/-0.49 before intake, 3.16+/-0.49 after intake; p=0.44). All predictor variables were used as dependent variables in a multiple regression model of the incremental change in CFVR after 2 weeks of chocolate intake. Intake of dark (but not white) chocolate, MDA-LDL, triglyceride (TG) and heart rate (HR) significantly influenced the change of CFVR after 2 weeks of intake (p<0.01) according to the multiple regression formula: Y=1.01X(1)-0.005X(2)-0.003X(3)-0.017X4 (Y=change in CFVR after 2 weeks of chocolate intake, X1=intake of dark (but not white) chocolate, X2=MDA-LDL, X3=TG, X4=HR).
Conclusion: Flavonoid-rich dark chocolate intake significantly improved coronary circulation in healthy adults, independent of changes in oxidative stress parameters, blood pressure and lipid profile, whereas non-flavonoid white chocolate had no such effects.