Inclusion Criteria:  Age: 20-45 years old 18. 5≤Body Mass Index≤ 23. 9 Normal oral diet  Exclusion Criteria:  People who have had or are suffering from urinary tract stones , or have the following diseases leading to the formation of stones: renal tubular acidosis, gout, hyperuricemia, chronic diarrhea, insulin resistance, hyperparathyroidism, idiopathic hypercalcemia, hypertension, diabetes mellitus CKD-EPI-eGFR<90ml/min1.73m-2) The following drugs are being used: cathartic, aspirin, angiotensin converting enzyme inhibitor，angiotensin II receptor antagonist，diuretic, acid inhibitor, alkali or carbonic anhydrase inhibitor, phosphorus binder, calcium agent and active vitamin D; Previous gastrointestinal diseases or gastrointestinal surgery Application of enteral and parenteral nutrition Complicated with infection, with or without antibiotic treatment Mental patients or unable to cooperate for various reasons