The purpose of this study is to determine whether low protein diet and very low protein diet supplemented keto-/amino acid is effective in preventing the progression of chronic kidney disease (CKD , stage 3b and 4).

Dietary protein restriction represents a basic therapeutic approach in chronic kidney disease(CKD), by reducing the accumulation of nitrogen catabolic substances, and by delaying the progress of CKD and proteinuria, but the effects of the different degree's protein diet on the renal progression remain to be determined.

The aim of this study is to evaluate the efficacy of low protein diet and α-keto acid tablet in retard the progress of CKD. This is a randomized, open-label, prospective study, 120 patients who meet inclusion and exclusion criteria will be randomized into three groups at the ratio of 1:1:1. Group I patients will receive low protein diet(0.6g/kg BW), group II will receive low protein diet supplemented with α-keto acid, while group III will take very low protein diet(0.3g/kg BW) supplemented with α-keto acid. The changes of glomerular filtration rate in CKD will be evaluated after 1 year treatment.

Inclusion Criteria:

• Patients with chronic kidney disease in stage 3b and 4(15ml/min/1.73m2<GFR<45 ml/min/1.73m2, estimated by EPI formula) receiving conservative treatment for CKD

Exclusion Criteria:

• With diagnosis of diabetic mellitus;
• Incapable of following study requirements to control diet;
• Glomerular filtration rate < 15 ml/min/1.73m2;
• Hypercalcemia or hyperkalemia (> normal upper limit);
• Other serious disease(eg.heart,lung,brain) within the last 3 months;
• Cardiac failure stage IV NYHA;
• With cirrhosis of liver or obvious symptoms of liver diseases, ALT or AST two times normal upper limit;
• Severe edema or serous cavity effusion;
• Drug abuse;
• Final diagnosis of malignant tumor;
• Receiving the long-term systematic steroid hormone or immunosuppressive agents(eg. Cyclophosphamidum,Cyclosporine, Prograf,Azathioprine) treatment;
• Gestation already, prepares to be pregnant in the period of the trial, lactating women;
• Participate in other product clinical trial within 30 days prior to this trial