Estimation of the oxalate content of foods and daily oxalate intake

Background The amount of oxalate ingested may be an important risk factor i n the development of idiopathic calcium oxalate nephrolithiasis. Reliable f ood tables listing the oxalate content of foods are currently not available . The aim of this research was to develop an accurate and reliable method t o measure the food content of oxalate. Methods. Capillary electrophoresis (CE) and ion chromatography (IC) were co mpared as direct techniques for the estimation of the oxalate content of fo ods. Foods were thoroughly homogenized in acid, heat extracted. and clarifi ed by centrifugation and filtration before dilution in water for analysis. Five individuals consuming self-selected diets maintained food records for three days to determine their mean daily oxalate intakes. Results. Both techniques were capable of adequately measuring the oxalate i n foods with a significant oxalate content. With foods of very low oxalate content (<1.8 mg/100 g), IC was more reliable than CE. The mean daily intak e of oxalate by the five individuals tested was 152 +/- 83 mg, ranging from 44 to 352 mg/day. Conclusions. CE appears to be the method of choice over IC for estimating t he oxalate content of foods with a medium (>10 mg/100 g) to high oxalate co ntent due to a faster analysis time and lower running costs, whereas IC may be better suited for the analysis of foods with a low oxalate content. Acc urate estimates of the oxalate content of foods should permit the role of d ietary oxalate in urinary oxalate excretion and stone formation to be: clar ified. Other factors. apart from the amount of oxalate ingested, appear to exert a major influence over the amount of oxalate excreted in the urine.