Daily doses of sugary soft drinks may make kidney stones more likely

THE QUESTION Regularly drinking a lot of fluids is considered one of the best ways to prevent kidney stones. But does the type of beverage make a difference?

THIS STUDY analyzed data on 194,095 adults, mostly middle-aged, who had never had kidney stones. In about an eight-year span, 4,462 developed them. People who reported drinking the most sugar-sweetened beverages were the most likely to have kidney stones. Those who drank one or more sugar-sweetened colas a day had a 23 percent higher risk than those who drank them once a week; risk for sugar-sweetened clear, non-cola sodas was 33 percent higher for those who drank one a day vs. one a week. On the other hand, some other beverages lowered risk for kidney stones when consumed once a day compared with once a week: Risk fell 26 percent for caffeinated coffee, 16 percent for decaffeinated coffee, 11 percent for tea, 31 percent for red wine and 33 percent for white wine, 41 percent for beer and 12 percent for orange juice.

WHO MAY BE AFFECTED? Adults. Anyone can get a kidney stone, though men get them more often than women and overweight people more than those of normal weight. They develop when certain substances in urine — calcium or uric acid, for instance — become too concentrated, forming a stonelike material. If big enough, kidney stones can block the urinary tract and lead to severe pain.

CAVEATS Information on beverage consumption came from the study participants’ responses on questionnaires. Serving sizes varied and included eight ounces for coffee and tea, five ounces for wine, a “small glass” for juices and a “glass, bottle or can” for sodas, with no size specified. The data did not differentiate between caffeinated and caffeine-free colas. Most participants were white; whether the findings would apply equally to other races is unclear.

FIND THIS STUDY May 15 online issue of the Clinical Journal of the American Society of Nephrology.

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The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.