Certain diet sodas may have the potential to prevent the most common type of kidney stone. In a study that is to be published in the June issue of Journal of Urology, researchers found that the diet versions of several popular citrus-flavoured sodas (such as 7Up, Sunkist and Sprite) contained relatively high amounts of citrate, known to inhibit the formation of calcium oxalate stones.
The findings suggest that diet sodas could be an extra weapon for some people prone to kidney stones.
Kidney stones develop when the urine contains more crystal-forming substances, such as calcium, uric acid and a compound called oxalate, than can be diluted by the available fluid. Most kidney stones are calcium-based, usually in combination with oxalate.
One reason that certain people are prone to stones is that their urine contains relatively little citrate, says Brian H. Eisner, an urologist at Massachusetts General Hospital in Boston, US, and lead researcher on the study.
Potassium citrate supplements have long been a common treatment for preventing calcium oxalate stones (as well as another type of stone, called uric acid stones). In a study 10 years ago, one of Dr Eisner’s colleagues found that a home-made lemonade concoction was effective at raising urine citrate levels in those prone to these stones.
The goal of this study was to see whether any commercially available drinks had a similar citrate content to home-made lemonade. The researchers chose diet soda, rather than regular soda, to avoid the high sugar and calorie content of the former. Overall, citrus-based diet sodas (including 7Up, Sunkist Orange, Sprite, Fresca and Canada Dry ginger ale) had somewhat higher citrate levels than the home-made lemonade. Dark colas, on the other hand, had little to no citrate.