Vitamin D plays an important role in the immune system. This study looked at vitamin D status and tuberculosis risk (1). Eight trials examined whether vitamin D as a therapy during tuberculosis treatment was useful. The studies varied substantially in a number of ways. One carefully performed study in which moderately large vitamin D doses were given to those who were vitamin D deficient and found a benefit sufficient to shortening treatment from 6 to 4 months, although other studies did not show this. Vitamin D is thought to have anti-inflammatory effects. A couple of studies reported some paradoxical inflammatory reactions. Future studies in patients with specific genetic backgrounds must monitor these events to discover underlying mechanisms.