Kidney stones are one of the most common disorders of a urinary tract infection. The biggest single thing you can do to prevent these painful stones is to drink at least two litres of fluid daily. And contrary to popular belief, it could help if some of this fluid is calcium-rich milk. A study in The New England Journal of Medicine found patients who’d had kidney stones formed of calcium were less likely to suffer from them again if they stuck to a normal calcium intake, compared with those who cut their intake. Low calcium intake increases excretion of a chemical called oxalate, which is the other component of calcium kidney stones. The right amount of calcium is 800mg a day – roughly 500ml of milk.