Studies have suggested dark chocolate is good for the heart

A top medical journal said any health claims about plain chocolate may be misleading.

Plain chocolate is naturally rich in flavanols, plant chemicals that are believed to protect the heart.

But an editorial in the Lancet points out that many manufacturers remove flavanols because of their bitter taste.

Instead, many products may just be abundant in fat and sugar - both of which are harmful to the heart and arteries, the journal reported.

Previous studies have suggested that plain chocolate can help protect the heart, lower blood pressure and aid tiredness.

The devil in the dark chocolate is the fat, sugar and calories it also contains The Lancet

But the Lancet said: "Dark chocolate can be deceptive.

"When chocolate manufacturers make confectionery, the natural cocoa solids can be darkened and the flavanols, which are bitter, removed, so even a dark-looking chocolate can have no flavanol.

"Consumers are also kept in the dark about the flavanol content of chocolate because manufacturers rarely label their products with this information."

And the journal also pointed out that even with flavanols present, chocolate-lovers should be mindful of the other contents.

"The devil in the dark chocolate is the fat, sugar and calories it also contains.

"To gain any health benefit, those who eat a moderate amount of flavanol-rich dark chocolate will have to balance the calories by reducing their intake of other foods - a tricky job for even the most ardent calorie counter.