Chromium is controversial.
There is no known biological role that the element plays in the body, however, Cr 3+is found in the body. A quick Internet search does find websites that claim it is needed to stabilize sugar and that it is also used in enzymes but the consensual opinion* seems to disagree with this.
* More on the consensual opinion tomorrow.
Chromium is still found in vitamin supplements. Why, I am not sure but probably due to the fact that there have actually been reported cases (three in total) of chromium deficiency (http://en.wikipedia.org/wiki/Chromium_deficiency) – although chromium deficiency still seems controversial.
Chromium is taken as the 3+ ion in vitamin supplements, often as chromium picolinate:
Image kindly reproduced according to the licence at: http://en.wikipedia.org/wiki/File:Chromium_picolinate.png
The other common ion of chromium is the 6+ ion. This is known to be carcinogenic and is the true story behind the award winning film Erin Brokovich.