It has been a stunning triumph of marketing and propaganda that many people believe that treatments that are “natural” are somehow magically safe and effective (an error in logic known as the naturalistic fallacy). There is now widespread belief that herbal remedies are not drugs or chemicals because they are natural. The allies in Congress of those who sell such products have even passed laws that embody this fallacy – taking herbal remedies away from FDA oversight and regulating them more like food than drugs.

The other major fallacy spread by the “natural remedy” industry is that if a product has been used for a long time (hundreds or thousands of years), then it must also be safe and effective because it has stood the test of time (this fallacy is referred to as the argument from antiquity).  This fallacy even has a specific regulatory term to invoke it – GRAS or “generally recognized as safe.” With food and food ingredients the FDA does not require evidence of safety if the ingredient is generally recognized as safe. This might make sense when referring to foods that have be eaten by humans for a long time. Although the logic is still dubious, it’s just practical – the FDA could not take upon itself the task of proving that every food eaten by humans has no significant negative health consequences. It is more a recognition of practicality than reality.

The GRAS principle, however, is misplaced when referring to herbal remedies, as is the naturalistic fallacy. Herbal remedies are drugs, plain and simple. They contain chemicals that are ingested on a regular basis for their pharmacological effects. The fact that they derive from plants is irrelevant. The fact that individual chemicals are not purified and given in precise amounts does not mean they are not pharmacologically active chemicals – it just means that when taking an herbal remedy you are getting a mixture of many chemicals in unknown doses.

Every now and then the public needs to be reminded of this fact. Recent studies of the effects of aristolochic acid on the renal system are a good opportunity to do so. Aristolochia is an herb that has been used for thousands of years in many cultures for many indications, such as child birth, weight loss, and joint pain. It is both “natural” and ancient. It is also a powerful nephrotoxin – it causes kidney damage.

This first came to world-wide attention in the 1990s when a group of Belgian women who were taking Chinese herbs as part of a weight loss regimen developed end-stage kidney failure. The syndrome became known as Chinese Herbs Nephropathy, and it was soon discovered that aristolochic acid was likely the culprit. It was later discovered that Endemic Balkan Nephropathy was also likely due to aristolochic acid – aristolochia seeds were being baked into bread and therefore consumed on a regular basis. Now some researchers are recommending that these two entities be combined into one – aristolochic acid nephropathy.

This latest research just published finds that use of aristolochia is linked to the high incidence of urinary tract cancer in Taiwan. The rate of urinary tract and renal cancer in Taiwan is about four times higher than in Western countries. This led the study authors to suspect there was an environmental cause, and they quickly suspected that aristolochia might be the culprit. Although use of aristolochia was banned in Taiwan in 2003, its use is still widespread. The study found that 60% of the 151 subjects with renal cancer studied had specific mutations that previous research has linked to aristolochia.

There is now extensive research demonstrating that aristolochic acid causes kidney damage and increases the risk for urinary tract cancers. This latest study adds to that growing evidence. And yet this connection was entirely unknown prior to the 1990s, despite thousands of years of use of aristolochia. This example just highlights the fact that widespread use of an herbal product, or any treatment, is not sufficient to ensure that it is safe, or even that it is effective. Common use may be enough to detect immediate or obvious effects, but not increased risk of developing disease over time. That requires careful epidemiology or specific clinical studies. We know about the risks of prescription drugs only because they are studied, and then tracked once they are on the market. Without similar study and tracking there is simply no way to know about the risks of herbal products. Relying upon “generally recognized as safe” is folly.

It is also interesting to consider how aristolochia came to be used to aid in the birthing process – one of its most popular uses and the source of its name, which means “noble birth” in Greek. As with the traditional use of many herbs, it appears to be based entirely on sympathetic magic – the belief that a plant will be useful for an indication based upon what the plant looks like. In this case the flower of many aristolochia species looks like a birthing womb. The rest is anecdote, placebo effect, and confirmation bias – but no science.

We cannot know how many people over the centuries have been harmed by the use of aristolochia, for indications for which there is no evidence or good reason to believe that the herb is effective. In short, aristolochia is both unsafe and ineffective. This has not stopped it from being a popular herbal remedy for thousands of years. So much for the naturalistic fallacy and the argument from antiquity.


Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.