Citrate, Malate and Alkali Content in Commonly Consumed Diet Sodas: Implications for Nephrolithiasis Treatment

Eisner, Brian H.; Asplin, John R.; Goldfarb, David S.; Ahmad, Ardalanejaz; Stoller, Marshall L.

doi:10.1016/j.juro.2010.02.2388

« Previous Next »The Journal of Urology
Volume 183, Issue 6 , Pages 2419-2423, June 2010

Citrate, Malate and Alkali Content in Commonly Consumed Diet Sodas: Implications for Nephrolithiasis Treatment

Brian H. Eisner
- Department of Urology, University of California-San Francisco, San Francisco, California
- Department of Urology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Correspondence: Department of Urology, GRB 1102, Massachusetts General Hospital, 55 Fruit St., Boston, Massachusetts 02114 (telephone: 617-726-3512; FAX: 617-726-6131)
- Financial interest and/or other relationship with Boston Scientific, PercSys and Ravine Group.
John R. Asplin
- Litholink Corp., Chicago, Illinois, and Nephrology Section, New York Harbor Veterans Affairs Medical Center, New York, New York
- Financial interest and/or other relationship with Ravine Group.
David S. Goldfarb
- Department of Urology, St. Vincent's Hospital and New York University School of Medicine, New York, New York
- Financial interest and/or other relationship with Ravine Group.
Ardalanejaz Ahmad
- Department of Urology, University of California-San Francisco, San Francisco, California
Marshall L. Stoller
- Department of Urology, University of California-San Francisco, San Francisco, California
- Financial interest and/or other relationship with PercSys and Ravine Group.

Received 11 September 2009 published online 19 April 2010.

Purpose

Citrate is a known inhibitor of calcium stone formation. Dietary citrate and alkali intake may have an effect on citraturia. Increasing alkali intake also increases urine pH, which can help prevent uric acid stones. We determined citrate, malate and total alkali concentrations in commonly consumed diet sodas to help direct dietary recommendations in patients with hypocitraturic calcium or uric acid nephrolithiasis.

Materials and Methods

Citrate and malate were measured in a lemonade beverage commonly used to treat hypocitraturic calcium nephrolithiasis and in 15 diet sodas. Anions were measured by ion chromatography. The pH of each beverage was measured to allow calculation of the unprotonated anion concentration using the known pK of citric and malic acid. Total alkali equivalents were calculated for each beverage. Statistical analysis was done using Pearson's correlation coefficient.

Results

Several sodas contained an amount of citrate equal to or greater than that of alkali and total alkali as a lemonade beverage commonly used to treat hypocitraturic calcium nephrolithiasis (6.30 mEq/l citrate as alkali and 6.30 as total alkali). These sodas were Diet Sunkist® Orange, Diet 7Up®, Sprite Zero™, Diet Canada Dry® Ginger Ale, Sierra Mist® Free, Diet Orange Crush®, Fresca® and Diet Mountain Dew®. Colas, including Caffeine Free Diet Coke®, Coke Zero™, Caffeine Free Diet Pepsi® and Diet Coke with Lime, had the lowest total alkali (less than 1.0 mEq/l). There was no significant correlation between beverage pH and total alkali content.

Conclusions

Several commonly consumed diet sodas contain moderate amounts of citrate as alkali and total alkali. This information is helpful for dietary recommendations in patients with calcium nephrolithiasis, specifically those with hypocitraturia. It may also be useful in patients with low urine pH and uric acid stones. Beverage malate content is also important since malate ingestion increases the total alkali delivered, which in turn augments citraturia and increases urine pH.

Key Words: kidney, carbonated beverages, nephrolithiasis, malic acid, alkalies