You need vitamin D to keep your bones strong. It also plays a role in how your immune system -- your body's defense against germs -- works.
If you have ulcerative colitis, especially if you need steroids, you may be at risk for having low levels of vitamin D.
A good source of vitamin D is dairy foods, but a lot of people with UC cut back on dairy to help them curb symptoms of diarrhea.
Experts have different views on vitamin D supplements, so ask your doctor if it it's a good idea for you to take them.