Dark chocolate could protect the cardiovascular system
support of the health benefits of eating dark chocolate are
stacking up. The latest research indicates that the flavonoid-rich
substance could have a protective effect on the cardiovascular
system, at least in the three hours immediately following
consumption, writes Jess Halliday.
The growing evidence in favor of real dark chocolate with a high cocoa content opens up possibilities for food formulators to use it as a functional ingredient, rather than just a flavour to draw sweet-toothed consumers to their products.
Researchers in Athens set out to investigate the effect of eating dark chocolate on three determinants of cardiovascular performance: endothelial function (lining of blood vessels, lymphatics, and serous cavities), arterial stiffness, and wave reflections. All three are predictors of cardiovascular risk.
Their interest was driven by previous research that has shown studies suggest that high intake of flavonoids, powerful antioxidants, delivers benefits to the cardiovascular system - and dark chocolate contains almost five times the flavonol content of apples.
"Our study shows for the first time that consumption of dark chocolate acutely decreases wave reflections, that it does not affect aortic stiffness, and that it may exert a beneficial effect on endothelial function in healthy adults," wrote the researchers in the American Journal of Hypertension (vol 18; issue 6; pp785-791).
For the latest randomized, single-blind, sham procedure-controlled, cross-over study, lead researcher Charalambos Vlachopoulos of Athens Medical School recruited 17 healthy young volunteers.
Over a three-hour period following the administration of 100g of commercially available dark chocolate, Vlachopoulos and colleagues measured the participants' endothelial function by flow-mediated dilation of the brachial artery (FMD), their wave reflections through the aortic augmentation index (AIx) and their aortic stiffness through carotid-femoral pulse wave velocity (PWD). Plasma oxidant status was evaluated with measurement of plasma malondialdehyde (MDA) and total antioxidant capacity (TAC).
They found that the chocolate led to a significant increase in resting and hyperemic brachial artery diameter throughout the three-hour period (by up to 0.15 mm and 0.18 mm, respectively).
At the one-hour mark, FMD was seen to increase significantly, with an absolute increase 1.43 percent. The AIx significantly decreased throughout the study (maximum absolute decrease 7.8 percent), indicating a decrease in wave reflections. PWV did not change significantly.
Plasma MDA and TAC did not change after the chocolate was eaten either - an interesting observation as it indicates that the benefits might not be attributed to the anti-oxidant effect of the flavonoids.
Instead, the researchers believe that the dilatory effect of chocolate under resting conditions might be attributable to one of four factors: improved nitric oxide bioavailability; prostacyclin increase; direct effect of chocolate in smooth muscle cells; or activation of central mechanisms.
Whatever the cause of the perceived benefits, they concluded: "Chocolate consumption may exert a protective effect on the cardiovascular system."
However the study was conducted over a very short period, which meant that it could not measure the longer-term effects of chocolate consumption - whether positive or negative. The researchers recommended that further studies be carried out to assess any long-term effects.
Other recent lines of inquiry into the health benefits of chocolate include a small study published in the March issue of American Journal of Clinical Nutrition suggesting that consumption of dark chocolate could improve glucose metabolism and decreases blood pressure.
In April a team from the Lombardi Comprehensive Cancer Center at Georgetown University revealed in Molecular Cancer Therapeutics that they had identified a compound in chocolate called pentameric procyanidin which is believed to activate a number of proteins responsible for the continual division of cancer cells, thereby thwarting the progression of breast cancer.
Nonetheless, despite the evidence of its health benefits, however, it is recommended that consumers do not rely on chocolate in place of other anti-oxidant containing foods, such as fruit vegetables and nuts, which also confer other health benefits.
The vast majority of chocolate on the market at present is sweetened confectionary with a low cocoa content, and is therefore more likely to be detrimental to good health than beneficial.