PROSPECTIVE-STUDY OF BEVERAGE USE AND THE RISK OF KIDNEY-STONES

Patients with kidney stones are routinely advised to increase their fl uid intake to decrease the risk of stone recurrence. However, there ha s been no detailed examination to determine whether the effect on recu rrence varies by the type of beverage consumed, The authors conducted a prospective study of the relation between the intake of 21 different beverages and the risk of symptomatic kidney stones in a cohort of 45 ,289 men, 40-75 years of age, who had no history of kidney stones, Bev erage use and other dietary information was measured by means of a sem iquantitative food frequency questionnaire in 1986. During 6 years of follow-up (242,100 person-years), 753 incident cases of kidney stones were documented. After adjusting simultaneously for age, dietary intak e of calcium, animal protein and potassium, thiazide use, geographic r egion, profession, and total fluid intake, consumption of specific bev erages significantly added to the prediction of kidney stone risk (p < 0.001), After mutually adjusting for the intake of other beverages, t he risk of stone formation decreased by the following amount for each 240-ml (8-oz) serving consumed daily: caffeinated coffee, 10% (95% con fidence interval 4-15%); decaffeinated coffee, 10% (3-16%); tea, 14% ( 5-22%); beer, 21% (12-30%); and wine, 39% (10-58%). For each 240-ml se wing consumed daily,the risk of stone formation increased by 35% (4-75 %) for apple juice and 37% (1-85%) for grapefruit juice. The authors c onclude that beverage type may have an effect on stone formation that involves more than additional fluid intake alone.