The goal of this clinical trial is to compare the safety and efficacy of nicotinamide mononucleotide (NMN) and placebo in patients with mild ulcerative colitis (UC). The main question it aims to answer is Whether NMN can alleviate the intestinal pathology of UC patients, so as to play a role in UC treatment or adjuvant therapy.

Participants will be randomized into two groups, an NMN group or a placebo group. Patients in the NMN group were treated with NMN intervention for 8 weeks. The placebo group received a placebo intervention for 8 weeks.

Inclusion Criteria:

1. Age ≥18 years old, ≤75 years old;
2. Clinical diagnosis of mild active UC patients, the diagnosis standard reference inflammatory bowel disease diagnosis and treatment of the consensus of opinion 2018.
3. Agreed to participate in this study, and sign the informed consent.

Exclusion Criteria:

1. Patients with ALT or AST more than 2 times the upper limit of normal, TBIL more than 2 times the upper limit of normal;
2. The creatinine clearance patients less than 60 ml/min.
3. The intestines or other parts have severely active infection patients need to use antibiotics or antiviral drugs;
4. Crohn's disease and intestinal tuberculosis and other chronic intestinal infectious disease, intestinal malignant tumor patients;
5. Pregnancy and lactation women;
6. People with diabetes or screening period more than 7.0 tendency for fasting glucose/L or glycosylated hemoglobin exceed 6.5%;
7. With serious mental illness, such as drugs and alcohol can't cooperate with the patients;
8. Participated in any other clinical investigator within 1 month before the screening period;
9. The researchers determine any other disease or condition is not suitable for patients participate in the study.

Some data underlying this trial cannot be shared publicly due to protection of participant's privacy.