title: A further study of oxalate bioavailability in foods.
abstract: We extended the study of oxalate bioavailability by testing 7 additional food items: brewed tea, tea with milk, turnip greens, okra, peanuts and almonds. Nine normal subjects ingested a large serving of each of these items. The bioavailable oxalate was calculated from the increment in urinary oxalate during 8 hours after ingestion and bioavailability was determined as the percentage of total oxalate content in a given food item represented by bioavailable oxalate. Brewed tea and tea with milk, with a high oxalate content, had a low bioavailable oxalate level (1.17 and 0.44 mg. per load) because of the low oxalate availability (bioavailability of 0.08 and 0.03%). Turnip greens, with a satisfactory oxalate bioavailability (5.8%), had a negligible effect on urinary oxalate excretion, since oxalate content was relatively low (12 mg. per load). Okra, with a moderate oxalate content (264 mg. per load) had a negligible bioavailable oxalate (0.28 mg. per load). Only peanuts and almonds provided a moderate increase in oxalate excretion (3 to 5 mg. per load) due to the modest oxalate content (116 and 131 mg. per load) and oxalate bioavailability (3.8 and 2.8%). Thus, the ability of various oxalate-rich foods to augment urinary oxalate excretion depends not only on oxalate content but on the bioavailability.
authors.affiliation: Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical School, Dallas 75235.
authors.forename: L J
authors.initials: LJ
authors.lastname: Brinkley
authors.forename: J
authors.initials: J
authors.lastname: Gregory
authors.forename: C Y
authors.initials: CY
authors.lastname: Pak
mesh_terms: D000328:Adult; D001682:Biological Availability; D005260:Female; D005502:Food; D006801:Humans; D008297:Male; D009754:Nuts / Q000032:analysis; D010070:Oxalates / Q000032:analysis / Q000493:pharmacokinetics* / Q000652:urine; D013662:Tea / Q000032:analysis; D014675:Vegetables / Q000032:analysis
chemical_list: D010070:Oxalates; D013662:Tea