1321 DIFFERENCES IN THE REPORTED OXALATE CONTENT OF FOODS: IMPLICATIONS FOR DESIGNING RESEARCH STUDIES AND FOR COUNSELING CALCIUM OXALATE STONE FORMERS

Abstract

You have accessJournal of UrologyStone Disease: Evaluation & Medical Management1 Apr 20101321 DIFFERENCES IN THE REPORTED OXALATE CONTENT OF FOODS: IMPLICATIONS FOR DESIGNING RESEARCH STUDIES AND FOR COUNSELING CALCIUM OXALATE STONE FORMERS Kristina Penniston, Katrina Wojciechowski, and Stephen Nakada Kristina PennistonKristina Penniston More articles by this author , Katrina WojciechowskiKatrina Wojciechowski More articles by this author , and Stephen NakadaStephen Nakada More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.906AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Although exogenous oxalate may account for as much as 50% of the urinary oxalate excretion in some individuals, the oxalate concentration of many foods is unknown. Moreover, reports of available foods are conflicting due to inter-laboratory variability and different analytical methods. Perhaps for this reason, food oxalate values are lacking from nearly all nutrient analysis software even though quantification of its intake by calcium oxalate stone formers could be used to drive nutrition therapy recommendations. We compared the reported food oxalate data available from two sources. METHODS We evaluated the dietary oxalate of stone-forming patients (n=62) using the one nutrient analysis system providing such values for the majority of its food items, the Nutrient Data Systems for Research (NDSR). Patients completed weighed 4-day diet records; data were entered into the software by a dietitian. We then compared the data for oxalate to a publicly-available database of reported oxalate values for foods (Harvard University) that were analyzed by a single laboratory using a validated and state-of-the-art (“gold standard”) analytical method. RESULTS The NDSR contains food oxalate values, derived from multiple sources, for 99% of its >18,000 items; many of these have negligible oxalate content. The number of foods analyzed for oxalate content and listed on the Harvard University-sponsored website is far fewer (n=536). A paired Student's t-test comparing foods for which comparative oxalate values were available revealed a lack of concordance between the databases (P=0.042). Especially variable were foods at the highest range of oxalate concentration (>200 mg oxalate/serving), such as spinach and rhubarb. While foods in some food groups, such as nuts & seeds, had high correlation between databases (R2=0.85), actual oxalate values were different (P=0.031). CONCLUSIONS Agreement is needed on what food oxalate values should be used in the design of dietary intervention trials and to maximize comparability between studies. Moreover, if dietary recommendations are to have maximum clinical value, food oxalate estimations should be not only accurate but reliably reported and publicly available. Although estimation of other aspects of a patient's diet (e.g., intake of Ca, Mg, phytate) may be necessary to estimate the true risk of dietary oxalate on stone formation, greater congruence on reported oxalate values of foods is needed. Madison, WI© 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e510 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information Kristina Penniston More articles by this author Katrina Wojciechowski More articles by this author Stephen Nakada More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...