I am not a fan of herbal supplements for many reasons. In short, herbs are drugs. Herbal products on the market are simply poorly regulated drugs that probably don’t work, have variable doses, often have contaminants, and may be incorrectly labeled. So, they are terrible drugs.

These disturbing facts are “greenwashed” by marketers of herbal products with the hype that such products are “natural.” That doesn’t change the fact that they are still dirty, poorly regulated drugs.

A recent study adds to the growing body of evidence that supports my summary above. A study published in BMC Medicine concluded:

Most of the herbal products tested were of poor quality, including considerable product substitution, contamination and use of fillers.

Specifically:

Most (59%) of the products tested contained DNA barcodes from plant species not listed on the labels. Although we were able to authenticate almost half (48%) of the products, one-third of these also contained contaminants and or fillers not listed on the label. Product substitution occurred in 30/44 of the products tested and only 2/12 companies had products without any substitution, contamination or fillers. Some of the contaminants we found pose serious health risks to consumers.

Product substitution means that, while it says “gingko biloba” on the label, the pills contained alfalfa. They found that 32% of the products did not contain the main ingredient, but did contain another species not on the label. In addition, 20% contained contaminants and 21% contained fillers not on the label. Overall only 41% of the products tested were accurately labeled, which means consumers were most likely to either not be getting the herbal product they paid for, and/or to be getting plant species that were not on the label.

The latter is the bigger problem, as some of the contaminant or substituted species could pose toxicity, allergy, or drug-drug interactions. For example, a St. John’s Wart product contained senna, which can cause diarrhea if used regularly. Some products contained wheat, and so look gluten-free on the label but aren’t.

This isn’t the first study to find that herbal products are often incorrectly labeled or contaminated. A 2004 study by Saper found that 20% of Ayurvedic supplements found in local Boston stores were contaminated with potentially toxic levels of heavy metals.

As an aside, there is a humorous criticism of the Saper study by an Indian Ayurvedic proponent, essentially claiming that 20% is not that bad, and the study is flawed and racist because the products studied were not real Ayurvedic medicine. The criticism does not include references to independent studies showing that the alleged high quality Indian herbal products are superior in any way. In any case, it misses the point, which was not to bash India (which is what the author thinks) but to show that what consumers are buying is frequently contaminated.

The author did not cite other research, probably because other research confirms the 20% figure. For example, a 2008 study published in JAMA found overall a 20% rate of heavy metal contamination in Ayurvedic herbal products purchased over the internet, whether they were manufactured in the US or India.

Systematic reviews also show that herbal products can have side effect and drug-drug interactions, although there is overall very poor data on such reactions.

Good manufacturing processes and regulations can solve many of these problems, although it would be difficult. The current study authors point out that many of the manufacturers of adulterated or substituted products seemed genuinely unaware of the problem, which might suggest that the problem is happening upstream, from the suppliers of the raw material. So any regulation would have to involve the entire production chain, with monitoring of the end products.

In his latest book, Paul Offit tells the story of attempting to regulate herbal product use in his hospital. Eventually he settled for one criterion, that the manufacturers provide documentation of what is actually in the products. They refused to do this. One has to wonder why.

Proper regulation of herbal products would be desirable – no one wants users of herbal products to suffer side effects from contaminants. However, such regulations would carry an unintended downside – it would make more respectable products that would still have a major problem. They generally don’t work.