I was scanning the scientific literature for some interesting herb or essential oil research to include in an article. As I was browsing, I got sidetracked by some common problems with the science on herbs and essential oils and wound up writing this instead. The problems I frequently encounter are the following:

1) The researchers often lack sufficient knowledge of the herb’s traditional use and dosage, or at least don’t demonstrate such knowledge in their research.
2) Information regarding the quality, source and identification of the herb or oil is often inadequate or missing.
3) Funding is frequently by for-profit industries, either pharmaceutical or phytopharmaceutical, which introduces potential for conflict of interest.
4) The “one-size-fits-all” and reductionist approaches to Western medicine and research doesn’t work with herbs, oils, or drugs for that matter.

1) The researchers often lack sufficient knowledge of the herb’s traditional use and dosage, or at least don’t demonstrate such knowledge in the research.

Researchers studying the effects of an herb (or essential oil) often do not have first hand knowledge of working with that herb. This is not unusual and not surprising. The situation is often the same in drug pharmacology. The difference is that with drug studies, the researchers use some precedent in the literature for usage and dosage of the drug to guide them. In addition, there may be a medical doctor with relevant experience involved with the study in some way, perhaps even directing the work.  In contrast, researchers often fail to consider precedents in herb usage, or fail to consult with an experienced herbalist in designing their studies. Perhaps this is due to a reluctance to look to herbal tradition, which is written off as anecdotal by most Western scientists.   Many herbs have centuries of documented usage contained in numerous herbals. Such information would be a reasonable starting point when studying the activity of an herb. There certainly are many contemporary herbalists who could be tapped for their working knowledge of herbs undergoing scientific study.

One outcome of this oversight is that the researcher misses the nuanced ways in which a particular herb is used; thus, the herb is investigated in an application, or in a manner, for which it is not normally used. In turn, the such testing lead to the erroneous conclusion that the herb “does not work”.

Another result of not considering the traditional herb usage is that the doses employed for the research may be irrelevant. On one hand, if herb dosage is too low, the herb is found “not to work”.  On the other hand, if excessive doses are tested, particularly of essential oils, then the finding is that the herb or oil is dangerous. An example of this is a recent study on Rosemary officinalis essential oil that was carried out in mice and rats and published in the journal Genetics and Molecular Research (1). The authors wanted to address the potential for toxicity from use of topical preparations containing rosemary essential oil, and from foods and beverages containing whole herb extracts or essential oil of rosemary. The conclusion of the study is that rosemary essential oil is genotoxic and mutagenic, that is it damages and causes mutations in the genome.

A significant problem with the study were the huge and irrelevant doses of essential oil used to challenge the rodent subjects: 200-2000mg of oil per kilogram (kg) of body weight. The ~0.1kg rats were given an individual dose ranging from 20 to 200mg of rosemary oil. For comparison, in French aromatherapy, medical dosing of essential oil in adult humans may be as high as 100-300mg per day, given in several smaller doses (2, 3). Let’s do the math. Say an average human adult weighs 70 kg — a little over 150 pounds. The medical dose of essential oil stated above, 100-300mg, would come out to 1.4-4.3 mg of oil per kg of body weight. Therefore, the rats in the study were given an essential oil dose that ranged from ~40 to 1400 times greater than a medicinal dose in humans. Moreover, the medicinal dose of essential oil in humans is many fold greater than the amount of essential oil found in commercial topical preparations, foods and beverages, the very preparations about which the authors were concerned.

So, the doses of rosemary essential oil assayed in the study would be the equivalent of a person ingesting from over a half ounce to almost 7 ounces of straight essential oil, in one sitting. Imagine taking a dose of an over-the-counter NSAID like Ibuprofen that was 40-1400 times larger than the recommended dose. What do you think would happen? An ER visit would be in your near future. Heck, even ingesting 40-1400 times more cheese spread than recommended would cause problems.

A related issue is the isolation and concentration of individual plant constituents for testing, leading to the exposure of the test subjects — usually rodents — to concentrations of compounds not encountered in nature. Such isolation and purification of plant constituents also removes the buffering capacity of other components in the chemically-complex plant extract. Take salicylic acid (essentially, aspirin), which was discovered in and isolated from plants. When ingested by itself, salicylic acid, or the synthetic derivative, acetylsalicylic acid, causes stomach upset by damaging the mucus membranes.  However, when taken in the context of meadowsweet (Filipendula ulmaria) extract, the salicylates are still analgesic, but the stomach lining is protected by other plant constituents.

2) Information regarding the quality, source and identification of the herb or oil is often missing.

The study discussed above illustrates this point as well. The oil tested was identified as Rosmarinus officinalis. However, there are three recognized chemotypes of Rosmarinus officinalis. Chemotypes are variants of the plant that have differing chemistry and activities from one another (3). Even if a reasonable dose of essential oil were used in the study, it would be difficult to make meaningful comparisons of the data with data from other studies without knowing which rosemary essential oil chemotype was tested.

3) Funding by for-profit industries, either pharmaceutical or phytopharmaceutical, which introduces potential conflict of interest.

Many herb and essential oil studies are funded at least in part by pharmaceutical companies whose interest does not lie in promoting inexpensive herbs that people can grow themselves. Some herb studies are funded by phytopharmaceutical companies, who do have an interest in positive findings. Either way, there are potential conflicts of interest.  While such financial links are now disclosed in research papers, this does not alleviate the conflict. This is not to say that all studies funded by industry are biased in some way. At a private research institute, I worked on a pilot study of a drug developed by a small pharmaceutical company. The drug was not effective and even though the results were negative, there was never any pressure to skew the outcome.

However, it remains that profits are a powerful influencing force.  As evidence, consider the case of Vioxx, a formerly FDA approved drug developed by Merck. Vioxx, which brought in billions of dollars, was put on the market in 1999 and then withdrawn in 2004. Merck was accused of withholding data from publication indicating that Vioxx increased the risk of heart attack* (4). Perhaps more significantly, Merck was accused of knowing the dangers of the drug while it was on the market (5). Merck has not admitted to any wrongdoing, but has paid tens of thousands of claims related to heart attacks and strokes (6).

It takes lots of money to do the research required to get FDA approval on a substance, money that industry has and universities and private research institutes do not.  There are multiple problems here, particularly when considering an inexpensive herb that has been taken by, perhaps, millions of people over centuries and has developed a reputation for efficacy and safety. These problems go beyond what I wish to cover here. The point is that when money and profits control the research on herbs, the following facts get obscured:  Herbs are generally cheap, safe (see my upcoming post entitled “Herbs are Safe”), and effective when the appropriate herb is used for the appropriate person…which leads to #4.
4) The “one-size-fits-all” and reductionist approaches to Western medicine and research doesn’t work with herbs, oils, or drugs for that matter.

Herbalists do not use herbs the way drugs are used in Western medicine. Western medicine and research usually takes a reductionist approach, dealing only with the disease a person has rather than dealing with the person the disease has (this is to paraphrase Hippocrates). Moreover, people have grown to expect the convenience of simply popping a pill without taking any other action towards bettering their health.  Herbalists take a holistic approach to working with a client. Palliative herbs are used together with herbs for rebalancing the system  and dealing with the source of the problem. These herbs, in turn, are part of a larger picture that includes nutritional and lifestyle alterations. A particular herb does not work for everyone; this is true for drugs also. One liver herb, say Oregon Grape, may be efficacious for one person, but exacerbate an imbalance in the next person, who requires a different liver herb. You can read an informative recollection by the late herbalist Michael Moore on this very point in the preface to his treatise on constitutional physiology (7).

A recent study (8) provides an example of trying to fit an herb into the western medical paradigm, and the results were, of course, picked up by the news media and used to broadcast that “Echinacea doesn’t work” (9). The main problem with the study is that they did not dispense echinacea in the form that an herbalist would use. An herbalist would use an easily assimilated tea, appropriately made extract or powder so that (i) more of the herb would be absorbed and (ii) the herb would enter the bloodstream more rapidly. In the study, echinacea was dispensed as a solid pill for convenience and for uniformity of the preparation.  In addition to dried echinacea root, the pill also contained calcium acid phosphate, cellulose, silica, sodium starch glycolate, hypromellose, and magnesium stearate. Such a pill may be effective when the active ingredient is a  purified or synthetic, concentrated chemical like ibuprofen.  Whether this is the case when the active ingredient is an unknown number of chemicals contained in plant material, who knows?  In the worst case taking echinacea in a solid pill with multiple inactive ingredients would likely reduce digestion and assimilation of the echinacea. It would at least slow assimilation compared to a traditional preparation. Regardless, from an herbalist’s perspective, there is no vitality left in such a preparation.

To be fair, it would be a logistical nightmare to research herbs the way that herbalists use them…tailoring a protocol for each person. Moreover, herbs are chemically complex, variable entities, while drugs are defined.  An herbalist can assess the quality and strength of an herbal preparation through experience and adjust accordingly when working with a client. In a research study, this is not so easy. However, it is not appropriate that herbs that have been used for centuries, if not millenia, should be discarded or disparaged because they do not function in the Western reductionist paradigm.

So, to wrap it up, I’m not implying that scientific research on herbs and essential oils is not useful. Nor am I implying that scientists should only study herbs if they’ve trained as herbalists. I believe that researchers lacking herbal knowledge should consult with someone who has this background; or,  at least read the traditional literature and use that as a starting point for designing their studies. This would prevent a lot of wasted time and resources, not to mention the knee-jerk headlines in the news media that such-and-such herb does not work or is dangerous, when evidence to the contrary has accumulated for, perhaps, millenia.


1) Maistro, EL, et al (2010) Genetics and Molecular Research. 9: 2113-22.
2) Cuba, R (2001)  International Journal of Aromatherapy. 11: 76-83.
3) Schnaubelt, K. (1998) Advanced Aromatherapy: The Science of Essential Oil Therapy. Healing Arts Press, Rochester, VT.
4) Curfman GD et al, 2005, NJAM, 353: 2813-4.
5) Stephenson, J (2004) Journal of the American Medical Association. 292: 2827.
6) Voreacos, D & A Johnson (2010) Bloomberg. July 27.
7) Moore, M. Principles and Practice of Constitutional Physiology for Herbalists. Southwest School of Botanical Medicine.
8) Barret, B et al (2010) Annals of Internal Medicine. 159: 763-77.
9) Nano, S. Associated Press, 21 Dec 2010.

*Along these lines, a report just came out in British Medical Journal that reviewed data from 31 clinical trials of over 116,000 people on the NSAIDs naproxen, Prexige (Novartis), Ibuprofin, diclofeac and Celebrex (Pfizer). The finding was that all of these drugs when taken long term increase the risk of heart attack and/or stroke, with 2 of the drugs causing a 4 fold increase in the risk of cardiovascular-related death (Trelle, S et al (2011) British Medical Journal).