Via WebMD:
Kidney stones form when urine in the kidney becomes supersaturated with stone-forming salts -- and when the urine doesn't contain enough stone-preventing substances. One of these substances is citrate.Technorati Tags: kidney stones, lemonade, nephrology, urology
For people prone to stones, doctors usually prescribe potassium citrate. It can be taken as a pill or in liquid form. But lemon juice is full of natural citrate.
When made into low-sugar or sugar-free lemonade, Nakada and colleagues found, lemon juice increases the amount of citrate in the urine to levels known to inhibit kidney stones. It doesn't work quite as well as potassium citrate. But for patients who'd rather avoid yet another medication, lemonade is an attractive alternative...
To make lemonade, Stoller, Nakada, and Kang recommend mixing 1/2 cup of concentrated lemon juice with 7 cups of water. A sugar substitute may be added to taste. Sugar should be avoided, as the extra calories in sugared lemonade are too much for most people's health.