Prunes' effect on the digestion is already well known, but now US scientists claim the fruit is good for bones too.

Growers in California are hailing the prune as a superfood after researchers at the University of Oklahoma found the dried fruit helped to fight the onset of osteoporosis in men. The study on rats found a diet rich in the fruit stopped bone mass deterioration, and pointed to the high levels of boron and potassium in prunes.

"We are delighted that this new research highlights the importance of eating foods rich in antioxidants, such as California prunes," said Esther Ritson, European marketing manager for California Prunes. "Consumers are now better educated about the benefits of healthy eating and we look forward to this being reflected in sales of California prunes in 2007."

As many as one in five men over the age of 50 will break a bone, mainly because of osteoporosis,

she said.