NEW research suggests daily consumption of dark chocolate or cocoa powder can actually lower blood pressure.
Although the effect was small, it was potentially enough to help protect people from heart disease, said experts.
Scientists analysed data from trials in which people consumed daily helpings of dark chocolate or cocoa powder. The chocolate products contained varying amounts of plant compounds called flavanols that are believed to benefit health.
A total of 856 people took part in 20 trials lasting an average of two to eight weeks. The most flavanol-rich chocolate or cocoa was found to lower blood pressure by an average of two to three millimetres of mercury.
When chocolate or cocoa powder was compared with flavanol-free products, the beneficial effects were more pronounced.
In this case, blood pressure reductions of up to four millimetres of mercury were seen.
The findings are published in the latest issue of The Cochrane Library, a collection of studies aimed at informing health care policy.
Lead researcher Dr Karin Ried, from the National Institute of Integrative Medicine in Melbourne, Australia, said: "Although we don't yet have evidence for any sustained decrease in blood pressure, the small reduction we saw over the short term might complement other treatment options and might contribute to reducing the risk of cardiovascular disease."
Flavanols in cocoa, the raw material from which chocolate is made, are believed to boost levels of nitric oxide in the body.
This in turn causes blood vessels to relax and widen, thereby reducing blood pressure, say scientists.
The link between cocoa and blood pressure first emerged from the indigenous people of San Blas Island in Central America. They drink flavanol-rich cocoa drinks every day and have normal blood pressure regardless of age.
Flavanol concentrations in cocoa and chocolate vary greatly between different products.
Longer trials are needed before conclusions could be drawn about the effects of cocoa flavanols on heart disease and stroke risk, said Dr Ried.
She added: "These trials should use flavanol-free products in the control groups to eliminate any potential effects of low-dose flavanol on blood pressure."
Ideally, an adult's blood pressure should be below 140/85mmHg (millimetres of mercury). The first figure is the systolic reading, which refers to the pressure with each heart beat. The second, the diastolic reading, measures the "resting" pressure between beats.
The British Heart Association warned of the downside of eating chocolate - large numbers of calories.
Victoria Taylor, senior dietician at the charity, said: "Although this review showed a small reduction in blood pressure, the findings are hampered by a lack of consistency between the studies. It's difficult to tell exactly what sort of quantities of flavanol-rich cocoa would be needed to observe a beneficial effect and the best way for people to obtain it.
"With most of the studies carried out over a short period of time it's also not possible to know for sure whether the benefits could be sustained in the long term. The 100g of chocolate that had to be consumed daily in a number of the studies would also come with 500 calories - that's a quarter of a woman's recommended daily intake.
"Beans, apricots, blackberries and apples also contain flavanols and, while containing lower amounts than in cocoa, they won't come with the unhealthy extras found in chocolate."
A small study funded by chocolate-maker Mars yesterday suggested that cocoa drinks may benefit the brain in old age.
Flavanol-rich cocoa was said to increase the mental performance of elderly volunteers after eight weeks.