Drinking plenty of fluids and eating little meat reduces the chance of developing kidney stones, according to the German Internists Association (BDI).

The BDI said that drinking between one-and-a-half and two litres of fluids daily kept the concentration of salts and metabolic products in the urine low. And moderate consumption of meat and sausage, it added, slowed the production of uric acid, which is often a component of kidney stones.

People susceptible to kidney stones should also restrict their intake of foods containing oxalic acid, such as spinach, rhubarb, beets, chocolate and both black and green tea. Oxalic acid combines with calcium to form crystal deposits in kidney tissue.

In Germany an estimated five to 10 per cent of the population suffers from kidney stones at least once in their life. Men are affected three times more frequently than women.