In 1994 Congress (pushed by Senators Harkin and Hatch) passed DSHEA (the Dietary Supplement Health and Education Act). As regular readers of SBM know, we are not generally happy about this law, which essentially deregulated the supplement industry. Under DSHEA supplements, a category which specifically was defined to include herbals, are regulated more like food than like medicinals.
Since then the flood-gates opened, and there has been open competition in the marketplace for supplement products. This has not resulted, I would argue, in better products – only in slicker and more deceptive claims. What research we have into popular herbals and supplements shows that they are generally worthless (except for targeted vitamin supplementation, which was already part of science-based medicine, and remains so).
A company can essentially put a random combination of plants and vitamins into a pill or liquid and then make whatever health claims they wish for their product, as long as they stay within the “structure-function” guidelines. This means they cannot claim to cure or treat a specific disease, but this has proven to be an insignificant limitation on marketing supplements.