A new study suggests that dark chocolate decrease the risk of a heart attack by up to 20%.

But the effect of chocolate is only observed in the individuals, who already have high blood pressure.

Researchers at the University of Adelaide found that dark chocolate considerably reduced the blood pressure in subjects with hypertension.

Chemicals called flanavols, which are present in high amounts in cocoa beans play an effective role in reducing high blood pressure.

Flanavols effectively stimulate the production of endothelial nitric oxide, which is responsible for dilating the blood vessels.

The researchers have established that consuming food products having high level of flanavols, could have an effect on blood pressure comparable to that formed by 30 minutes of exercise.

But the study did not recommend the replacement of hypertension drugs with black chocolate, as high level of sugar and fat found in the snacks could have an injurious effect on the heart.

"The practicability of chocolate or cocoa drinks as long-term treatment is questionable," said researcher Dr. Karin Ried.

Researchers have found that consumption can extensively decrease blood pressure for people with high blood pressure but not for people, who have normal blood pressure. The study was published in the journal BMC Medicine.