Inclusion Criteria:  . Patients aged 30-90 years with diagnosis of CKD (defined as abovementioned). . Sign the inform consent and agree to participate in this study. . Compliant to low protein diet (defined as protein intake <0.8 g/Kg/day) for 4 weeks assessed by 24h urine urea estimates, before enrollment  Exclusion Criteria:  . History of any malignancy, liver cirrhosis, intestinal operation, irritable bowel syndrome, cardiovascular disease (defined as myocardial infarction, documented Q wave on EKG, unstable angina, coronary artery disease with stenosis > 75%, congestive heart failure with Ejection Fraction < 50% and cerebrovascular disease) in the past 3 months. . History of or infection disease requiring admission in the past 3 months or, concomitant antibiotics use. . Concomitant use of probiotics or prebiotics. . Pregnancy. . Renal transplant recipients.