慢性腎臟病的飲食治療新進展

Update of Dietary Management in Chronic Kidney Disease Patients

楊智宇(Chih-Yu Yang) ； 唐德成(Der-Cherng Tarng)

《內科學誌》 30卷2期 (2019/04) Pp. 65-69

https://doi.org/10.6314/JIMT.201904_30(2).02

摘要

慢性腎臟病病人的飲食控制，需考量五大要素，分別是水份、尿毒素、鉀離子、磷離子、與酸，與三高的控制相同，這五大要素的控制不限於藥物，良好的飲食治療亦扮演極重要的角色。地中海飲食成份富含腸道益菌所嗜食之果寡糖（fructo-oligosaccharides）與膳食纖維（dietary fiber），腸道益菌行發酵作用分解糖類（saccharolysis）產出短鏈脂肪酸，如此腸道環境有助於益菌存活，建構平衡（symbiosis）的腸道菌相。須特別注意的是，對於進入慢性腎臟病晚期的病人而言，地中海飲食中所強調的蔬果或穀物堅果具『鉀』與『磷』離子過量的疑慮，故蔬菜須先川燙處理且捨棄菜湯，並選擇低鉀水果，而不應一昧地避免食用蔬果，導致膳食纖維攝取不足，進而惡化腸道菌相。至於高磷的穀物堅果則少量攝取即可，同時避免食用富含無機磷的加工食品。相對於地中海飲食，西方飲食則富含腸道壞菌則嗜食的成份，如色胺酸（tryptophan）此胺基酸經由腸道壞菌行腐敗作用（proteolysis），分解為吲哚（indole），吲哚於人體內代謝成為硫酸吲哚酚（indoxyl sulfate），此為一親蛋白質尿毒素，慢性腎臟病者排泄硫酸吲哚酚的能力下降，導致硫酸吲哚酚累積，血中濃度上升，硫酸吲哚酚不僅對於血管細胞有毒性，同時會加速腎臟功能惡化，導致惡性循環。慢性腎臟病病人的照護牽一髮而動全身，提供病人全方位的照護，將有助於病人選擇飲食時毋須捉襟見肘，而是吃得健康、生活多采多姿。

關鍵字

慢性腎臟病（Chronic kidney disease） ； 腸道菌相（Gut microbiota） ； 菌相失衡（Microbial dysbiosis） ； 硫酸吲哚酚（Indoxyl sulfate）

並列摘要

The kidney is responsible for the excretion of body water, uremic toxins, phosphorus, postassium, and acid. Patients with chronic kidney disease (CKD) shouldn't depend on medical treatment, but should put more emphasis on dietary management instead. Mediterranean diet is rich in dietary fiber and fructo-oligosaccharides, i.e. the prebiotics, which are consumed by the healthy gut microbial flora. These beneficial microorganisms, i.e. the probiotics, produce short-chain fatty acids via saccharolysis, a process of fermentation, and create an environment of microbial symbiosis in human gut. Of note, the vegetables and fruits which Mediterranean diet highlights are rich in potassium. Therefore, vegetables should be pre-treated by boiling in water before ingestion, and fruits should be properly selected to ensure sufficient dietary fiber intake in patients with advanced CKD, instead of directly avoiding potassium-rich foods. Grains, nuts, and yogurt, which are also key elements of Mediterranean diet, contain plenty of organic phosphorus and should be restricted in patients with advanced CKD. However, it's even more essential to avoid the exposure of inorganic phosphorus, which usually exists in processed foods. In contrast to Mediterranean diet, Western diet lacks dietary fiber and is characterized by red meat, animal fat, sweetened food, and salts instead, which might result in gut microbial dysbiosis. Of note, the amino acid tryptophan is consumed by the gut microbial flora, which produces indole through proteolysis, a process of putrefaction. Indole is then absorbed via gut villi and enters the portal system of liver, where it is then sulfated and metabolized into indoxyl sulfate. Indoxyl sulfate is a protein-bound small molecule uremic toxin and is harmful to various cells, particularly vascular endothelial cells. In CKD patients, the excretion of indoxyl sulfate is impaired, and it is thus accumulated in the body and leads to a vicious cycle. In conclusion, CKD patients are at risks for gut dysbiosis, partly results from dietary restrictions of potassium and/or phosphorus. An integrative care involving comprehensive dietary instruction allows CKD patients to ensure dietary fiber intake, which might be beneficial not only for gut peristalsis but also to restore gut microbial symbiosis.