A recent scientific study published in JAMA (Journal of the American Medical Association) looked at the drug silymarin for the treatment of liver disease due to chronic hepatitis C that has not responded to standard therapy with interferons. This would be just another obscure study except for the fact that silymarin is an extract of milk thistle, an herb commonly used to treat liver disease. Further, the study was funded in part by the NCCAM (National Center for Complementary and Alternative Medicine).
The study represents one more in a long line of studies of herbal remedies funded by the NCCAM - all negative. There have now been large, double-blind clinical trials of echinacea and cold symptoms, gingko biloba and memory loss or Alzheimer's disease, black cohosh and hot flashes, saw palmetto and benign prostatic hypertrophy, and others. Even St. John's Wort, which is supposed to be a big herbal remedy win, has been shown to have no effect on moderate or severe depression (although the jury is still out on minor depressive symptoms).
Despite this string of negative studies, the herbal remedy industry continues to rake in billions of dollars a year. Large, rigorous, and negative studies seem to have little impact on the sales of herbal products overall (although they may effect the relative popularity of specific herbs to some extent).
To make matters worse, in the US herbal drugs were essentially deregulated in 1994 by the Dietary Supplement Health and Education Act (DSHEA). Herbs are now regulated more like food rather than drugs. Further, a special category of health claims, so-called structure function claims, was carved out for supplements. Companies can market herbs without any prior approval from the FDA or need to provide evidence of safety or effectiveness. They can even claim that their product supports the structure or function of the body in some way, as long as they don't mention a specific disease by name. This amounts to a massive loop hole through which any savvy marketer can drive a truck.
The deal that DSHEA and NCCAM made with the public was this - let the supplement industry have free reign to market untested products with unsupported claims and then we'll fund reliable studies to arm the public with scientific information so they can make good decisions for themselves. This "experiment" (really just a gift to the supplement industry) has been a dismal failure.
The result has been an explosion of the supplement industry flooding the marketplace with useless products and false claims. The only result has been to part the American public from billions of health care dollars over the last couple of decades.
Part of the problem is that negative studies are too easy to dismiss. In every case the supplement industry found some reason to minimize the implications of the studies showing their products do not work, instead preferring to cherry pick small and unreliable studies with positive results. No study can possibly address every possible permutation of how an herb can be used.
For example, herbal apologists claim that the dose was not high enough, the wrong part of the plant was used, the preparation was not correct, or the treatment population was wrong in some way. For echinacea they claimed that the wrong cold viruses were used. There is always something they can point to. Of course, if it's so difficult to find the right preparation for the right condition, they how do they justify selling highly variable products to the general population with broad claims?
It should be up to the manufacturer and marketer of an herbal product to prove that their product is safe and effective for whatever it is they claim it treats. Not only is this not required under DSHEA, companies can continue to market their herbs with claims that have been contradicted by major scientific studies funded by taxpayer dollars.
We can now add milk thistle for liver disease to the list of failed herbal remedies. Of course, this study only involved hepatitis C. There are many other forms of liver disease, and until every single one is studies in a major clinical trial at sufficient doses and duration, sellers can continue to hold out the claim that milk thistle works for something. They have no burden of proof, so all they need is a little denial.
Steven Novella, M.D. is the JREF's Senior Fellow and Director of the JREF’s Science-Based Medicine project.
Dr. Novella is an academic clinical neurologist at Yale University School of Medicine. He is the president and co-founder of the New England Skeptical Society and the host and producer of the popular weekly science show, The Skeptics’ Guide to the Universe. He also authors the NeuroLogica Blog.