Aims:Retrospectively observe the effects of Caltrate supplementation on the clinical effect of mesalazine in patients with ulcerative colitis.

Design: From January 2015 to December 2020, through retrieving the clinical database of the Second Affiliated Hospital of Wenzhou Medical University, patients with active UC who accepted mesalazine treatment were enrolled. According to whether Caltrate was supplemented at the same time, the patients were divided into supplementary group and non-supplementary group. The modified Mayo score and several laboratory indicators were compared between the two groups.

1. The research has been approved by the Medical Ethics Committee of the Second Affiliated Hospital of Wenzhou Medical University.

2. According to the "Consensus on Diagnosis and Treatment of Inflammatory Bowel Disease" formulated by the Beijing Conference in 2018 as a standard, patients with clear diagnosis of UC are collected. Exclusion criteria included: history of vitamin D treatment within the previous 3 months; treated with glucocorticoids, immunosuppressants, biologic agents, or colectomy during the follow-up; severe liver and kidney dysfunction; other autoimmune diseases.

3. Assess disease activity of UC participants based on the "Mayo score".

4. General information about participants with UC is collected.

5. Serum C-reactive protein, erythrocyte sedimentation rate, white blood cells, albumin, creatinine, calcium and phosphorus levels are measured.

6. The level of serum 25 (OH) D of participants is detected.

7. Participants are divided into two groups, one group was given oral Caltrate 0.6g/d +Mesalazine, and the other group only took Mesalazine .

8. The above serum indicators are re-measured in the 12th month, and the condition of UC participants is also evaluated.

9. Follow-up for 12 months. By comparing the above indicators, observe that in the Han population:

   1. Can Caltrate supplementation increase serum 25 (OH) D levels in patients with UC?
   2. Can Caltrate supplementation improve the condition of patients with UC?
   3. Whether Caltrate works synergistically with Mesalazine?
   4. whether the effect of Caltrate on UC patients is affected by factors such as disease site, disease activity, treatment, etc ..

10. Through statistical analysis, comprehensive analysis of the effectiveness and safety of Caltrate supplementation in Han patients with UC, providing a theoretical basis for further "precise treatment" intervention in inflammatory bowel disease.

Inclusion Criteria:

• Clearly diagnosed patients with UC
• Took mesalazine for at least 12 months

Exclusion Criteria:

• had recent supplementation of vitD3
• had prior or concomitant use of other biologic agent, glucocorticoid and/or immunomodulators at the time of enrollment or follow up
• Co-morbid with other autoimmune diseases
• Severe liver and kidney dysfunction

Chinese

Data sets will be made available on relevant requests and in accordance with journal guidelines when publishing results from this study.