Sirich Tammy L
Departments of Medicine, VA Palo Alto Health Care System and Stanford University, Palo Alto, California.
Semin Dial. 2015 Jan-Feb;28(1):75-80. doi: 10.1111/sdi.12315. Epub 2014 Oct 16.
Prior to the availability of hemodialysis, dietary protein restriction played a large part in the treatment of uremia. This therapy was based on observations that uremic symptoms increased with high protein intake. Early investigators thus presumed that "uremic toxins" were derived from the breakdown of dietary protein; its restriction improved uremic symptoms but caused malnutrition. After the availability of hemodialysis, protein restriction was no longer recommended. Studies in healthy subjects have shown that an intake of 0.6-0.8 g/kg/day is adequate to prevent protein malnutrition. Guidelines for hemodialysis patients, however, currently recommend higher protein intakes of 1.2 g/kg/day. A downside to higher intake may be increased production of protein-derived uremic solutes that caused the symptoms observed by early investigators. Some of these solutes are produced by colon microbes acting on protein which escapes digestion in the small intestine. Increasing dietary fiber may reduce the production of colon-derived solutes in hemodialysis patients without adverse effects of protein restriction. Fiber comprises carbohydrates and related substances that are resistant to digestion in the small intestine. Upon delivery to the colon, fiber is broken down to short chain fatty acids, providing energy to both the microbes and the host. With an increased energy supply, the microbes can incorporate dietary protein for growth rather than breaking them down to uremic solutes. Increasing fiber intake in hemodialysis patients has been shown to reduce the plasma levels of selected colon-derived solutes. Further studies are needed to test whether this provides clinical benefit.
在血液透析出现之前，饮食蛋白质限制在尿毒症治疗中发挥了很大作用。这种疗法基于这样的观察结果：高蛋白摄入会使尿毒症症状加重。因此，早期研究人员推测“尿毒症毒素”源自饮食蛋白质的分解；限制蛋白质摄入可改善尿毒症症状，但会导致营养不良。血液透析出现后，不再推荐限制蛋白质摄入。对健康受试者的研究表明，每天摄入0.6 - 0.8克/千克体重足以预防蛋白质营养不良。然而，目前针对血液透析患者的指南推荐更高的蛋白质摄入量，即每天1.2克/千克体重。较高摄入量的一个缺点可能是蛋白质源性尿毒症溶质的产生增加，这正是早期研究人员所观察到的症状的原因。其中一些溶质是由结肠微生物作用于在小肠中未被消化的蛋白质产生的。增加膳食纤维摄入量可能会减少血液透析患者结肠源性溶质的产生，且不会产生蛋白质限制的不良影响。膳食纤维由碳水化合物及相关物质组成，它们在小肠中难以被消化。进入结肠后，膳食纤维会被分解为短链脂肪酸，为微生物和宿主提供能量。随着能量供应增加，微生物可以利用饮食蛋白质进行生长，而不是将它们分解为尿毒症溶质。研究表明，增加血液透析患者的膳食纤维摄入量可降低特定结肠源性溶质的血浆水平。还需要进一步研究来检验这是否具有临床益处。
