I just recently saw a report of a potential problem with Chromium Picolinate - may or may not be a problem until more studies or done but be careful with high doses. Here is a statement about the problem I found searching on Yahoo:

This report was taken from the December issue of the GASEB Journal, a publication of the Federation of American Societies of experimental Biology. It reported that Chromium Picolinate was found to be clastogenic, meaning that it damaged chromosomes, but his finding doesn't necessarily mean that it is carcinogenic, or a definite substance or agent that produces cancer.

The fact that a substance damages chromosomes is considered a good indicator of its carcinogenicity. "This is the first test to directly link carcinogenicity to a form of chromium that is used as a supplement: it predicts, not proves that Chromium Picolinate is a human carcinogen." The research reported that not only did chromium picolinate damage chromosomes, but so too did
picolinic acid when tested alone, although to a lesser extent.