Assessment of citrate concentrations in citrus fruit-based juices and beverages: implications for management of hypocitraturic nephrolithiasis.

摘要

BACKGROUND AND PURPOSE: Dietary intake of citrate in the form of citrus juices (eg, lemonade, orange juice) will enhance urinary citrate excretion, a valuable benefit for patients with hypocitraturic calcium oxalate nephrolithiasis. While information on citrate concentrations in select citrus juices is available, data on citrate concentrations of commercially available beverages (juice and otherwise) are limited. Using nuclear magnetic resonance spectroscopy (1H NMR), we report citrate concentrations of several beverages to help guide dietary recommendations aimed at increasing urinary citrate excretion and correcting hypocitraturia. METHODS: Citrate concentrations of a squeezed lemon, several fruit juices, and common beverages were measured using 1H NMR. Spectra for each sample were obtained in duplicate; citrate peak was identified, measured, and quantified and compared with the citrate concentration in the juice of 1 medium lemon. RESULTS: Quantitative analysis revealed the highest concentration of citrate was in grapefruit juice (64.7 mmol/L), followed in decreasing concentrations by lemon juice (47.66 mmol/L), orange juice (47.36 mmol/L), pineapple juice (41.57 mmol/L), reconstituted lemonade (38.65 mmol/L), lemonade flavored Crystal Light (38.39 mmol/L), ready to consume not from concentrate lemonade (38.24 mmol/L), cranberry juice (19.87 mmol/L), lemon-flavored Gatorade (19.82 mmol/L), homemade lemonade (17.42 mmol/L), Mountain Dew (8.84 mmol/L), and Diet 7Up (7.98 mmol/L), respectively. CONCLUSIONS: According to 1H NMR, all of the tested "natural" citrus juices have high concentrations of citrate (38.3-67.4 mmol/L), with grapefruit juice having the highest concentration of the beverages chosen. Lemonade flavored Crystal Light had the highest concentration of citrate in the nonjuice category of tested beverages. In patients with mild to moderate hypocitraturia, dietary supplementation with citrus-based juices may be an effective alternative to medical management while not requiring large serving sizes. Further prospective studies are warranted to evaluate the clinical significance of these findings.