Dark choclolate may soon find an unexpected place on the menus of those hoping to reduce their risk of heart disease. Cocoa is a rich source of flavonoids, a plant chemical which has proved useful in blocking cardiovascular disease.
The British Association for the Advancement of Science annual Festival of Science opened yesterday on an optimistic note with talks on how cocoa and some chocolate products might actually do good.
Far from being just an indulgence, the flavonoids contained in cocoa are powerful antioxidants which fight cell damage. These chemicals also reduce the risk of unwanted blood-clotting, make the vascular system less reactive to stresses and may diminish the likelihood of damaging inflammation.
Flavonoids occur in a wide variety of foods, according to Prof Catherine Rice-Evans, of King's College, London, but dark chocolate is a particularly good source. A single 50g bar has the same amount of flavonoids as a kilogramme of onions, 1.1 litres of blackcurrant juice, six apples or 15 oranges.
Beer is a poor source of flavonoids, with four litres needed to match a single chocolate bar, and white wine is no better, with 4.2 litres required, but red wine is a good source, according to Prof Rice-Evans. Two glasses of red wine can deliver as much flavonoid as a 50g chocolate bar.
Prof Carl Keen, of the University of California, explained how these plant-derived phyto chemicals are beneficial. He has run a series of trials to measure the bioavailability of flavonoids after eating chocolate and what these chemicals do to platelets, the cells which cause blood clots to form.
Unwanted blood clots cause serious problems in patients with cardiovascular disease, leading to heart attacks or strokes. These clots form spontaneously when platelet activation occurs too readily. It is now common practice for these patients to take one "baby" aspirin each day to reduce platelet activation.
Chocolate flavonoids have a similar effect. Platelet activation was reduced within an hour after patients ate 27g of dark chocolate, according to Prof Keen.
This "marked reduction" persisted for six hours before platelet activity returned to its original condition. The reduction was typical of that achieved in those taking daily aspirin.
"The data are coming in fairly strongly in favour of [flavon oids]", Prof Keen said. "It is everything in moderation. The effect we see on blood-clotting is minor but significant."
Asked how this might reduce the presumed risk of deep vein thrombosis or clotting in people who have completed long flights, he said that no study had been done on this. However, the chocolate flavonoids changed platelet activity in a "very rapid" way and he admitted to taking a small amount of chocolate before flying over from the US, adding: "It couldn't hurt."
Dr Harold Schmitz, of the chocolate manufacturer Mars Inc, responded to questions about the risks posed by the fats and sugars in chocolate. He acknowledged that while eating chocolate did produce more fat, the fat was not essential to the action of the flavonoids.
He also said that the amount of flavonoid received per calorie consumed was higher with cocoa than with many other foods. People should also be aware that cocoa-processing tended to destroy the useful flavonoids unless manufacturers took care to protect them.
While many dark chocolate products retained flavonoids, no cocoa or chocolate drink product currently on the market left the flavonoids in the drink, so these were of no benefit to consumers.
