A few squares of dark chocolate a day could cut the risk of serious heart disease. Researches at the University Hospital in Zurich studied a group of smokers who showed early signs of heart disease.

The smokers consumed 40 grams of dark chocolate and shortly after showed improved artery function.

Lead author Roberto Corti says improvement is probably due to the high cocoa content of the chocolate - 74 percent.

Dark Chocolate is also rich in antioxidants, which -- like wine, tea and berries - help prevent damage to the heart. But, Dr. Corti warns too much chocolate could increase other cardiovascular risk factors like elevating blood sugar levels, body fat and body weight.

His advice to smokers is to stop smoking.

White chocolate showed no beneficial effects. The study was published in the journal Heart.