Inclusion Criteria:  Age 18~60 years. Grade 1 hypertension and part of prehypertension (initial diagnosis or free from antihypertensive drugs within 2 weeks): 130 mmHg ≤ Average office SBP < 160 mmHg, and/or 85 mmHg ≤ Average office DBP < 100 mmHg, according to the "2018 Chinese Guidelines for Prevention and Treatment of Hypertension" and "National guideline for hypertension management in China (2019)". Patients with informed consent after thorough explanation.  Exclusion Criteria:  Antibiotics or probiotics usage within the last 2 weeks. Participants of other clinical trials currently or within last 3 months. Antihypertensive medications usage currently or within last 2 weeks. Diagnosed secondary hypertension History of diabetes mellitus. History of peripheral atherosclerosis. Severe hepatic or renal diseases (ALT >3 times the upper limit of normal value, or end-stage renal disease on dialysis or eGFR <30 mL/min/1.73 m2, or serum creatinine >2.5 mg/dl [>221 μmol/L]). History of stroke (not including lacunar infarction and transient ischemic attack [TIA]). History of coronary heart disease. Sustained atrial fibrillation or arrhythmias at recruitment disturbing the electronic BP measurement. NYHA class III-IV heart failure; Hospitalization for chronic heart failure exacerbation within last 6 months. Severe valvular diseases; Potential for surgery or percutaneous valve replacement within the study period. Dilated cardiomyopathy; Hypertrophic cardiomyopathy; Rheumatic heart disease; Congenital heart disease. Other severe diseases influencing the entry or survival of participants, such as malignant tumor or acquired immune deficiency syndrome. Cognitive impairment or severe neuropsychiatric comorbidities who are incapable of providing their own informed consent. Participants preparing for or under pregnancy and/or lactation. With special diet habits, such as vegetarians. Active gastritis or enteritis; gastrointestinal ulcers or bleeding; post-gastrointestinal surgery, such as intestinal excision. Other conditions inappropriate for recruitment according to the investigators.