Investigation of the role of dietary myo-inositol hexakisphosphate (phytate) on the relative risk of calcium oxalate kidney stone formation in black and white male South African subjects
Master Thesis
2005
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University of Cape Town
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Abstract
Previous studies have shown that caJclum oxalate (CaOx) stone-formers have lower urinary concentrations of myo-inositol hexakisphosphate (phytate or IPe) than healthy individuals, that dietary intake of this substance leads to its increased urinary excretion and that it is an inhibitor of CaOx nucleation and growth In South Africa it has been reported that the black population has a higher dietary phytate intake than whites. The present study was undertaken to test the hypothesis that South African black subjects have higher urinary phytate levels than their white cOLlflterparts and that this contributes to the relative rarity of caOx kidney stone disease in this population group A modified indirect extraction/photometry method to measure urinary IPe was designed, developed and tested in the present study. This assay was then used to measure IPo in the urine of rural black and urban white subjects while on their free unrestricted diets In addition, urban black and white subjects each followed IPo-restricted followed by lPG-rich dietary protocols for a period of three days Urines were collected after administration of each protocol and were again analysed for IPe using the newly developed assay. Urines were then used in several crystallization experiments to measure the CaOx metastable limit, "C-oxalate deposition kinetics and inhiOition of CaOx crystal aggregation. The results showed that while on their free diets, rural blacks excreted significantly less IPs than urban whites despite their previously reported higher dietary intake of this substance This suggests that the renal handling of dietary IP
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Lesotho, N. 2005. Investigation of the role of dietary myo-inositol hexakisphosphate (phytate) on the relative risk of calcium oxalate kidney stone formation in black and white male South African subjects. University of Cape Town.