IMPACT OF DIETARY CALCIUM AND OXALATE RATIOS, AND OXALOBACTER FORMIGENES COLONIZ

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 流行病学研究表明，低钙和高草酸盐摄入量是草酸钙肾结石形成的危险因素。草酸盐通常与肠道中的钙形成络合物，形成不溶于水的晶体，这些晶体在粪便中被排出。我们已经证明，在控制草酸含量的饮食中，尿草酸排泄量与草酸摄入量成正比，这与结石形成的风险直接相关。产草酸草杆菌已被确定为降解人类粪便中草酸的主要微生物，因此假设与该微生物定居以限制结石风险。这种非致病的厌氧细菌使用草酸作为其主要碳源，将其转化为甲酸盐和二氧化碳。几项研究表明，草酸钙结石患者比非结石患者更不可能有Oxf。到目前为止，大多数饮食研究都在膳食中使用固定比例的钙和草酸。这可能并不能真正代表大多数美国人的正常饮食模式。我们认为，在每顿饭中保持钙和草酸盐摄入量的最佳平衡可能会限制草酸盐排泄增加的一过性发作，从而降低结石风险。我们进一步提出，这种尿草酸排泄的暂时性增加在非殖民者中更大。这项研究将比较殖民和非殖民个体对钙与草酸比例平衡和不平衡饮食的反应。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Epidemiological studies have indicated that low calcium and high oxalate intakes are risk factors for the formation of calcium oxalate kidney stones. Oxalate normally complexes with calcium in the intestine forming insoluble cyrstals which are eliminated in the fecal stream. We have shown using diets controlled in oxalate content that urinary oxalate excretion is proportional to the amount of oxalate ingested which is directly correlated with the risk of stone formation. Oxalobacter formigenes has been identified as the predominant organism degrading oxalate in human feces so colonization with this organism has been hypothesized to limit stone risk. This non-pathogenic, anaerobic bacterium uses oxalate as its main carbon source, converting it to formate and carbon dioxide. Several studies have suggested that calcium oxalate stone formers are less likely to have OxF than non-stone formers. Most dietary studies to date have used a constant ratio of calcium to oxalate in meals. This may not truly represent the normal dietary patterns in most of the U.S. population. We propose that maintaining an optimal balance between calcium and oxalate intake with each meal may limit transient episodes of increased oxalate excretion and thus reduce stone risk. We further propose that such transient increases in urinary oxalate excretion are greater in non-colonized individuals. This study will compare the response of colonized and non-colonized individuals to diets balanced and imbalanced in their calcium to oxalate ratios.