Why is there a lack of evidence about complementary and alternative treatments?

One reason for the lack of research in complementary and alternative treatments is that large, carefully controlled medical studies are costly. Trials for conventional medications or procedures are often directly or indirectly funded by the government or drug companies, giving conventional treatments more resources to do studies. Most complementary and alternative treatment trials are more difficult to fund, so there are fewer trials. Nonetheless, a number of studies are currently under way on complementary and alternative treatments ranging from herbs to yoga that may help identify what works and what doesn't, and what's safe and what isn't. In fact, the U.S. government has established a National Center for Complementary and Alternative Medicine to help guide the public in making wise choices when it comes to complementary and alternative treatments.