Dark chocolate could potentially reduce both cardiovascular and thromboembolic disease, due to its high flavonoid-rich cocoa content, suggests new research on chocolate consumption.
The findings were announced by researchers from the University of Dundee in Scotland who were performing the first study to examine the effects of whole-chocolate consumption on ex vivo platelet function, which they say have shown that dark chocolate acutely reduces collagen-stimulated platelet aggregation and reduces plasma nitric oxide (NO) production.
The researchers believe these results provide evidence that dark chocolate has the potential to reduce both cardiovascular disease and thromboembolic disease.
Previous studies with a cocoa beverage demonstrated an ex vivo and in vitro platelet effect, notes lead researcher G Kennedy. The cocoa fraction of chocolate contains flavonoids, which reduce platelet activation and hence atherogenesis and cardiovascular disease.
Flavonoids are also found in red wine, fruit, and vegetables, and form the basis for the cardioprotective mechanism in the so-called 'French paradox', the low rate of ischemic cardiovascular disease seen in a population that consumes a diet high in dietary fats and oils. The Dundee researchers further reported that dark chocolate has a higher flavonoid concentration than either milk or white chocolate.
The single-investigator, blind, randomised study examined the ex vivo effects of chocolate on platelet activity in healthy volunteers. Individuals with a history of cardiovascular disease were excluded from the study, and all volunteers were free from platelet-modifying agents (e.g. aspirin) for 14 days before and after the study. The subjects did not eat any chocolate between study visits.
Thirty subjects were randomised to receive 100 grams of white (0 per cent cocoa), milk (25 per cent cocoa), or dark (70 per cent cocoa) chocolate. Pre-chocolate, baseline, and 4-hour post-chocolate venous blood samples were obtained, and three measures of platelet function were obtained: platelet-rich plasma aggregation (PRPA), whole-blood platelet aggregation (WBPA), and platelet NO production.
White chocolate was found to have no effect on ex vivo platelet function. Milk chocolate was associated with a trend toward reduced PRPA, but this did not reach statistical significance, according to the researchers. Milk chocolate had no effect on NO.
Dark chocolate, however, was found to reduce both 0.5- and 1-mcg/mL collagen-stimulated PRPA by 92 per cent and 12 per cent respectively. No significant changes were seen in the dark-chocolate group following ADP stimulation of the platelets. All WBPA was reduced, but significantly only for WBPA stimulated with 1 mcg/mL collagen. Dark chocolate was also associated with a reduction in plasma NO (6.2 micromol/L to 4.6 micromol/L) and a significant reduction in ADP-stimulated aggregation (9.6 micromol/L to 8.3 micromol/L). Kennedy G Dark presented the study findings 'Dark chocolate inhibits platelet aggregation in healthy volunteers' at the XIX Congress of the International Society on Thrombosis and Haemostasis in Birmingham, UK, 12-18 July 2003. Full details of the study can be found in the Journal of Thrombosis and Haemostasis 2003; 1 Supplement 1 July.