The studies used various curcumin formulations and doses (0.1–10 grams), and the intervention duration ranged from 1 to 6 months.

In the context of ulcerative colitis, curcumin (vs. a placebo) improved the chances of:

Clinical remission (no longer having symptoms of ulcerative colitis) by 145%
Clinical response (a substantial decrease in symptoms of ulcerative colitis) by 93%
Endoscopic remission (no longer having ulcerative colitis, as diagnosed visually by a colonoscopy) by 281%, but this finding was not statistically significant(p=0.06)

Taking curcumin had no more effect on the chances of clinical or endoscopic remission of Crohn’s disease than a placebo did.

Can curcumin improve inflammatory bowel disease? Original paper