LETTER
Grapefruit Juice and Kidney Stones
Barbara Ameer, PharmD
1 December 1998 | Volume 129 Issue 11 Part 1 | Page 913
TO THE EDITOR:
Of 17 beverages evaluated in Curhan and colleagues' cohort of more than 80 000 women in the United States, grapefruit juice was the only drink associated with increased risk for kidney stones [1]. This new health concern can be added to concern raised by the evidence of increased oral drug bioavailability by grapefruit juice [2].
The mechanisms of these physiologic effects need to be elucidated. In the case of drug interactions, one or more components of grapefruit juice is thought to inhibit metabolic enzymes in the gastrointestinal tract or to inhibit a P-glycoprotein pump that transports drugs and other chemicals through membranes. The mechanism for kidney stone formation by grapefruit juice is more speculative; Curhan and colleagues note that it is unlikely to be related to alteration of urinary pH or absorption of oxalate [1].
Numerous phenolic compounds can bind divalent cations. As an in vitro test of oxidation of low-density lipoproteins, inhibition of Cu2±catalyzed oxidation of low-density lipoprotein is a model widely used to evaluate antioxidant potential of flavonoid and flavonoid-like constituents of fruits and their juices, vegetables, and teas [3]. Flavanones are the type of flavonoid abundant in grapefruit; the predominant flavanone is naringin. It occurs only rarely in noncitrus plants and may confer properties unique to grapefruit juice. It is interesting to speculate whether naringin, which is excreted in the urine [4], binds to calcium and delivers it to the renal system, thus increasing the chance of stone formation because of high renal concentrations of calcium.
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Author and Article Information
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Princeton Jct, NJ 08550
1. Curhan GC, Willett WC, Speizer FE, Stampfer MJ. Beverage use and risk for kidney stones in women. Ann Intern Med. 1998; 128:534-40.
2. Ameer B, Weintraub RA. Drug interactions with grapefruit juice. Clin Pharmacokinet. 1997; 33:103-21.
3. Vinson JA, Jang J, Dabbagh YA, Serry MM, Cai S. Plant polyphenols exhibit lipoprotein-bound antioxidant activity using an in vitro oxidation model for heart disease. J Agric Food Chem. 1998; 43:2798-9.
4. Ameer B, Weintraub RA, Johnson JV, Yost RA, Rouseff RL. Flavanone absorption after naringin, hesperidin and citrus administration. Clin Pharmacol Ther. 1996; 60:34-40.
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