The old slogan "Guinness is Good For You" may actually be true, according to new medical research that suggests the stout may help prevent heart attacks.

University researchers in the US claim that drinking a pint of the black stuff each day may be as effective in preventing heart attacks as an aspirin because it can reduce heart clots.

Trials at the University of Wisconsin used dogs with narrowed arteries similar to those in people with heart disease to compare effects of drinking stout with those of drinking lager.

They found Guinness reduced clotting activity but lager did not.

The research concluded that the "antioxidant compounds" found in Guinness are similar to those found in certain fruits and vegetables, making the stout work as well as aspirin in the prevention of heart clots.