There is almost none. Since 1994, the “Dietary Supplement Health and Education Act” essentially deregulated the supplement industry, and placed them outside the authority of the FDA. As a result, supplement sales have skyrocketed, and more are introduced every year, with claims of health benefits from increasing memory to preventing cancer. But there is scant evidence to support any of these claims.
The Wall Street Journal reports that the US government is funding more research:
Helping to spur the research initiative are the Office of Dietary Supplements and the National Center for Complementary and Alternative Medicine, both part of the National Institutes of Health. The agencies last month awarded grants totaling about $37 million to five dietary supplement research centers, expanding a program that has already awarded more than $250 million in research grants for herbs and botanicals since 2002.
Unfortunately, I’m not convinced that the science, if negative, will convince anyone. There may be promise in some of these botanicals, and this article mentions a few claims that actually have been substantiated. But the research showing no effect of ginkgo biloba hasn’t stopped its mass-market appeal. To it’s credit, the government does try to educate the public on supplements, but I think a change in law is necessary. Anyone making a claim about health benefits, whether it’s for drugs, food, or supplements, needs to back those claims up with evidence.