Beverage use and the risk of kidney stones in women
ASN 30th Annual Meeting, San Antonio
J Am Soc Nephrol (Sep) 8:560A 1997
The beverage ingestion of 81,094 women in the Nurses' Health Study, age 40-65 years, was compared in stone formers vs. non-stone formers. These women had not previously had stones; over an 8 year period of study, 699 cases of kidney stones were documented. Semiquantitative food frequency questionnaires were used to to measure beverage and nutrient intake. The effects of age, nutrient intake and total fluid intake were controlled.
The result was that coffee, decaf coffee and tea had small effects to reduce the risk of stones by 8-10% for every 240 ml serving and wine (color not specified) reduced risk by more than 50%. Grapefruit juice on the other hand increased risk by 39% (95% CI 3-87%). Twelve other beverages including beer and soda had no demonstrable effect. The results, including the effect of grapefruit juice, were similar to the authors' report in men (Am J Epidemiol 143:240; 1996).
Comment: The effects of few beverages have been studied prospectively. Various deleterious effects are assigned to them nonetheless. Tea is supposed to have oxalates; caffeine inhibits ADH; soda is supposed to have significant phosphate content or lead to calciuria due to the sucrose load. Citrus juices have both citrate (inhibitory) and oxalate (lithogenic) so that the net effect is nil. Grapefruit juice has been thought to be high in oxalate but more modern analytic techniques claim this fact is not true. Grapefruit juice also clearly has distinct effects on blood levels of several drugs, such as diltiazem and cyclosporine. Beer has also been shown in similar fashion to be possibly protective.
These contradictory facts stem from the lack of data that include prospective urinary supersaturation measurements, the difficulties in the past of measuring oxalate, and the relative lack of knowledge about oxalate bioavailability from varying foods and beverages. Of course the present study also cannot explain its findings on the basis of changes in urinary chemistry. As the authors admit, the lack of stone analyses is another shortcoming, though it is fair to assume as they do that most stones are calcium oxalate. Finally the influence of these beverages on lithogenicity in patients known to have stones may be somewhat different. The credibility of this study is enhanced by the similarities of its findings to those of the authors' previous study in men. (David S. Goldfarb, M.D., NYU School of Medicine)
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ASN 30th Annual Meeting, San Antonio
Nephrolithiasis : Renal Stones: Treatment