More Options

Herbs Are Drugs

The Science of Medicine

Steven Novella

Skeptical Inquirer Volume 37.2, March/April 2013

Herbal supplements are big business. In the United States alone, 2011 sales of all herbal products were estimated to be $5.3 billion (Blu­menthal et al. 2012). Meanwhile the industry has managed to maintain a “mom and pop” image to the public, the righteous underdog constantly under attack by Big Pharma. In reality, the herbal product industry is just another drug industry, one selling products that are poorly regulated and likely don’t work for their claimed indications.

There are already a fair number of scientific studies looking at various herbal products for specific indications. There is nothing inherently implausible about the usefulness of plant-based remedies. Many modern drugs are derived from plants. Plant parts contain many substances, some of which are pharmacologically active and can be exploited for medical use.

The deception inherent to the herbal product industry, in my opinion, is the notion that herbs are something other than drugs. This is closely tied to the naturalistic fallacy: the idea that a substance that is “natural” (a poorly defined concept) is somehow magically safe and effective.

Here are some useful tips for the potential herbal product user:

  • Don’t be reassured by claims that a product is “natural”
  • Traditional use, whether genuine or not, is not by itself a good predictor of safety or effectiveness
  • Find out what the best scientific evidence says, and seek out critical information specifically
  • Respect the fact that herbs are drugs, which means:
    • They can cause toxicity and side effects
    • They can interact with other drugs you are taking
    • You should inform your physicians about any herbal products you are taking (just as you list your prescription medications)

In reality, herbs often contain multiple active ingredients that potentially have drug-like activity in the body. These drugs are often poorly understood, may not even be identified, and exist in highly variable doses within herbal products (Wurglics et al. 2001). Herbs have drug-drug interactions and the same potential for side effects and toxicity as any drug, mitigated only by the fact that herbal products generally contain low doses of active ingredients.

Some popular herbal products have been studied in standard placebo-controlled trials, and they have generally not fared well. A recent scientific study published in the Journal of the American Medical Association, for example, 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 (Fried et al. 2012). Silymarin is an extract of milk thistle, an herb commonly used to treat liver disease.

There have now been large, double-blind clinical trials of echinacea and cold symptoms (Barret et al. 2002; Taylor et al. 2003; Turner et al. 2005), Gingko biloba and memory loss or Alzheimer’s disease (Snitz et al. 2009), black cohosh and hot flashes (Newton et al. 2006), saw palmetto and benign prostatic hypertrophy (Tacklind et al. 2009), 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; see Hypericum Depression Trial Study Group 2002). Many of these studies were funded by the National Center for Complementary and Alternative Medicine (NCCAM).

Despite this string of negative studies, the herbal remedy industry continues to rake in billions of dollars every year. Large, rigorous, and negative studies seem to have little impact on the sales of herbal products overall (although they may affect the relative popularity of specific herbs to some extent).

To make matters worse, in the United States 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 loophole easily exploited by any savvy marketer.

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.

Part of the problem is that negative studies are too easy to dismiss. In every case the supplement industry finds 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 may 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, this logic works both ways: if it’s so difficult to find the right preparation for the right condition, then how do they justify selling highly variable products to the general population with broad claims?

How are the “traditional” uses of herbal products derived in the first place? The impression that is often given is that centuries of successful traditional use is behind many herbal product claims, but this is often a modern marketing fiction.

It seems reasonable to require manufacturers and marketers of herbal products 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.

As with many things, the marketing of herbal products is largely based on ideology and a compelling narrative rather than actual science and evidence. For the most part consumers are left to their own devices to sort out which products are likely to be useful.

Finally, keep in mind that if an herbal product contains a useful active ingredient, it would likely be identified, purified, and properly studied. The best result is likely to come from taking a precisely measured amount of a specific active ingredient with known pharmacokinetics and pharmacodynamics as well as drug-drug interactions.

Herbs are not only drugs, they are a mixture of various drugs of unknown dose, activity, and interactions, often with evidence that they do not work. It takes effective marketing to convince the public this is somehow better than taking highly purified and studied pharmaceuticals.


Barrett, B.P., R.L. Brown, K. Locken, et al. 2002. Treatment of the common cold with unrefined echinacea: A randomized, double-blind, placebo-controlled trial. Annals of Internal Medicine 137(12): 939–946.

Blumenthal, M., A. Lindstrom, C. Ooyen, et al. 2012. Herb supplement sales increase 4.5% in 2011. HerbalGram 95: 60–64. Online at

Fried, M.W., V.J. Navarro, N. Afdhal, et al. 2012. Effect of silymarin (milk thistle) on liver disease in patients with chronic hepatitis C unsuccessfully treated with interferon therapy, a randomized controlled trial. Journal of the American Medical Association 308(3): 274–282. doi:10.1001/jama.2012.8265.

Hypericum Depression Trial Study Group. 2002. Effect of Hypericum perforatum (St John’s Wort) in major depressive disorder: A randomized controlled trial. Journal of the American Medical Association 287(14): 1807–14.

Newton, K.M., S.D. Reed, A.Z. LaCroix, et al. Treatment of vasomotor symptoms of menopause with black cohosh, multibotanicals, soy, hormone therapy, or placebo: A randomized trial. Annals of Internal Medicine 145(12): 869–79.

Snitz, B.E., E.S. O’Meara, M.C. Carlson, et al. 2009. Ginkgo biloba for preventing cognitive decline in older adults: A randomized trial. Journal of the American Medical Association 302(24): 2663–2670. doi:10.1001/jama.2009.1913.

Tacklind, J., R. MacDonald, I. Rutks, et al. 2009. Serenoa repens for benign prostatic hyperplasia. Cochrane Database of Systematic Reviews (April 15) (2):CD001423. doi: 10.1002/14651858.CD001423.pub2.

Taylor, J.A., W. Weber, L. Standish, et al. 2003. Efficacy and safety of echinacea in treating upper respiratory tract infections in children: A randomized controlled trial. Journal of the American Medical Association 290(21): 2824–2830.

Turner, R.B., R. Bauer, K. Woelkart, et al. 2005. An evaluation of Echinacea angustifolia in experimental rhinovirus infections. New England Journal of Medicine 353(4): 341–348.

Wurglics, M., K. Westerhoff, A. Kaunzinger, et al. 2001. Comparison of German St. John’s Wort products according to hyperforin and total hypericin content. Journal of the American Pharmaceutical Association (Wash) 41(4): 560–66.

Steven Novella

Steven Novella's photo

Steven Novella, MD, is an assistant professor of neurology at Yale University School of Medicine. He is the host of the Skeptics’ Guide to the Universe podcast, author of the NeuroLogica blog, executive editor of the Science-Based Medicine blog, and president of The New England Skeptical Society.