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News to get your heart racing: the effects of chocolate, energy drinks and blood type

We start today with what could, for many, be the greatest bit of news they hear this year: chocolate could help reduce blood pressure.

The Cochrane Group's report in the Lancet said flavanols, which are found in cocoa, produce nitric oxide, which relaxes blood vessels.

The analysis of 20 previous studies showed that there had been mixed results, but the overall picture was that cocoa resulted in a 2-3mmHg reduction in blood pressure, the BBC reports.

However, there is a warning: dark chocolate contains fewer flavanols than you might think because they are often removed due to their bitter taste, the Lancet says.

In slightly less surprising news, the Daily Mail reports that energy drinks mixed with alcohol increase the risks of heart palpitations and disturbed sleep.

Research by the University of Tasmania in the Alcoholism: Clinical & Experimental Research journal found that partygoers who used energy drinks with alcohol were six times as likely to suffer heart palpitations as those who drank alcohol straight or with a normal soft drink.

They also had four times the odds of sleep difficulties and were more prone to tremors, irritability and short bursts of energy followed by exhaustion.

However, contrary to previous belief, the study of 403 men and women aged between 18 and 35 found energy drink fans were less likely to take risks when drinking.

Staying on heart conditions, research in the American Heart Association Journal has shown that people from blood groups A, B and AB are more at risk of heart disease than those with blood type O.

The most vulnerable are those with blood type AB – they are 23% more likely to suffer from heart disease than those with blood group O, the BBC reports.

For individuals with blood group B the risk of heart disease increased by 11%, and for blood type A, by 5%.

However, researchers do not yet know why this is.