OBJECTIVE:Dietary phytate (IP6) enjoys a reputation as an inhibitor of calcium renal stone formation, although there are very few human studies to support this notion. In South Africa, urolithiasis occurs in the white (W) but is rare in the black (B) population. We undertook this unique human model to further investigate the IP6 theory. METHODS:Healthy W and B males completed baseline food-frequency recall questionnaires. Dietary intake of IP6 was restricted for 18 days. An IP6 dietary supplement was ingested on days 15-18. Twenty-four-hour urinary phytate and other urinary components were determined. Relative supersaturations of calcium salts were calculated. The urinary metastable limit (MSL) of calcium oxalate (CaOx) and its crystallisation kinetics were determined experimentally. RESULTS:Habitual dietary intake of IP6 and its urinary excretion were significantly higher in B than in W (1650 ± 202 vs. 640 ± 134 mg/d, P = .0002 and 1.13 ± 0.12 vs. 0.75 ± 0.13 μM, P <.05, respectively). In B, urinary phytate decreased significantly after 15 days of IP6 restriction, but in W, its excretion remained constant. After supplementation, urinary IP6 increased significantly in both groups reaching levels commensurate with the baseline value in B. No significant differences occurred in B in any of the routine urinary risk factors throughout the trial. However, in W, urinary citrate excretion increased on day 18 relative to day 0. There were no significant intragroup or intergroup changes in relative supersaturation, metastable limit, or crystallization kinetics. CONCLUSIONS:Despite notable differences in the renal handling of ingested IP6, there were no changes in any of the well-established urinary risk factors for calcium renal stone formation in either of our uniquely different test groups. We conclude that, in the absence of hard evidence, claims that IP6 is a stone inhibitor remain unproven.

译文

目的:膳食植酸(IP6)作为抑制肾结石形成的钙素而享有盛誉,尽管很少有人类研究支持这种观点。在南非,尿石症发生在白人(W)人群中,但在黑人(B)人群中很少见。我们采用了这种独特的人类模型来进一步研究IP6理论。
方法:健康的W和B男性完成了基线食物频率召回问卷。 IP6的饮食限制为18天。在第15-18天摄入IP6膳食补充剂。测定了二十四小时的尿肌醇六磷酸和其他尿液成分。计算了钙盐的相对过饱和度。草酸钙(CaOx)的尿亚稳态极限(MSL)及其结晶动力学是通过实验确定的。
结果:B的日常饮食摄入IP6及其尿排泄量显着高于W(1650±202 vs. 640±134 mg / d,P = .0002和1.13±0.12 vs. 0.75±0.13μM,P <。分别为05)。在B中,IP6限制15天后,尿肌醇六磷酸显着减少,但在W中,其排泄量保持恒定。补充后,两组的尿中IP6均显着升高,达到与B的基线值相当的水平。在整个试验中,B中的任何常规尿液危险因素均无显着差异。但是,在W中,相对于第0天,第18天尿液中柠檬酸盐的排泄量增加。相对过饱和度,亚稳态极限或结晶动力学方面,组内或组间无明显变化。
结论:尽管摄入的IP6在肾脏处理方面存在显着差异,但在我们两个不同的测试组中,任何公认的尿钙钙结石形成的危险因素均无变化。我们得出的结论是,在没有确凿证据的情况下,声称IP6是结石抑制剂的说法仍未得到证实。

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