Research of Aromatic Materials: What Do We Really Know?
A while back, information was released regarding an ongoing study that I had issues with due to its vague details, bias, and flaws. After much thought, I realized that it was not so much just that particular study that I had a problem with, as that it was the proverbial straw that broke the camel’s back.
For various reasons over the last few years, I have spent a lot of time reading research papers related to Aromatherapy and its various aromatic materials. It is hard enough when looking at this info to remember to pay close attention to the specifics presented. For example:
- Are we sure that it is talking about the use of essential oils?
- Is it instead referring to the plant as a whole, or some other type of extract such as a CO2, tincture, absolute, etc.?
These things matter as the differences in the chemical profile and potency of these products can make a huge difference in the results.
However, a problem arises when you start to notice that there are definite issues with some published papers that make relying on them even more difficult. It has been argued that if you look hard enough, you can find a study to back up anything. That is why it is so important to have better guidelines that are readily available to all and universally used, that can help add more validity to these studies. The following are several things that, to me, are problems and shortcomings in some existing papers and research.
What Was Used?
One of the first problems is the sometimes lack of specific information for the aromatic that is being addressed. For instance, I have seen a paper talking about Lavender, but there was little to no information about whether they were talking about the whole plant itself, or some other form. In one paper it stated that they were using the essential oil, then further down it appeared that they were actually using an alcohol extraction. That leaves one to question if they did not use what they intended to use, or were they just using the wrong terminology? Several times it seemed like the people doing the study did not know enough about what they were working with, nor did it seem like they had consulted with anyone who did.
Even once it is established that a paper is referring to the desired material, which for the purposes of this article is an essential oil, that leads to a whole new set of questions that one should keep in mind when evaluating the research. For instance:
- Was the essential oil produced by distillation, or in the case of citrus, was it instead produced by expression/cold-pressing of the peel?
- Is the binomial botanical name included along with the full common name for clarification? For example, if they were doing a study on Lavender, can we be sure that they actually used Lavandula angustifolia, or did they use Spike Lavender (Lavandula latifolia), Spanish Lavender (Lavandula stoechas), or Lavandin (Lavandula x intermedia) instead?
- Depending on the oil, was the chemotype or variety noted if applicable?
- Where was the plant material used to make the oil sourced from?
- What part of the plant was used?
- Was the oil rectified or deterpenated?
- Where did they obtain the oils themselves? Are we sure that they came from a reputable supplier of pure, good-quality oils, or did they come from somewhere that is known for synthetic or adulterated ones?
Sometimes researchers distill the plant material for the studies themselves. If this is the case:
- Where was the plant material harvested?
- When was it harvested?
- How was it prepared, distilled, etc.?
These factors alone can make a huge difference in the chemistry of an essential oil.
- Is the resulting distilled oil comparable to the artisan or commercially produced counterpart that is sold for aromatherapy use?
- Was a proper GC/MS report included, and who performed it? On more than one occasion, I have seen studies in which the constituents were either misidentified on a GC/MS, or the wrong oil or plant material was used.
- How were the oils stored (oxygen exposure, heat, light, contaminants) leading up to and during the study? There have been issues in studies that did not use the proper lab equipment. For example, some plastics were used instead of glass, resulting in a reaction with the oils, causing contamination.
All of these things can make a major difference in the outcome of the study.
If a paper included a GC/MS analysis performed by a knowledgeable chemist in the industry, if they were also consulted about materials and storage, and it was all documented, then we would know exactly what was used and be able to eliminate so many of these questions. How can we really be sure about the validity of a study without really knowing what all went into it?
While there are guidelines currently available, different publications and organizations can (and do) have different requirements. The most comprehensive and most recognized are the CONSORT (Consolidated Standards of Reporting Trials) guidelines. However, these still do not include all the factors mentioned above, and not all types of research utilize them. Hopefully in the future these guidelines, or something similar, will be expanded and universally required across all types of aromatic materials research.
What is Really Being Said?
It can be very hard at times to navigate studies. In addition to trying to make sure that you know exactly what you are looking at (as mentioned above), there is the added difficulty of not seeing the big picture if you do not have access to the full paper.
Some do a really good job of summarizing everything so that the abstract really does give a good idea of what is in the paper, but in the end, it is still just a summary. Most of the details are in the full paper, and you have to read the whole thing to know for certain what all the facts are.
Which brings me to what I like to call Loch Ness studies. The ones in which the abstracts look excellent, and does the majority of the paper, except for that one little section in the discussion or conclusion in which the researchers reveal that their initial expectations were wrong. I have seen a few of these used as references to support essential oil actions, only to look up and read the whole paper and see that the actual findings do not support the same conclusion that the abstract and most of the paper seem to indicate that it does. That just goes to show that due to the way these are worded, they can be misleading and easily misinterpreted by anyone. It is really important to read the entire paper and pay close attention to all of the details.
However, do not get me wrong, negative results are just as important to research as the positive ones, and they do not need to be omitted or hidden.
When negative results aren’t published in high-impact journals, other scientists can’t learn from them and end up repeating failed experiments, leading to a waste of public funds and a delay in genuine progress. (Mehta, 2019)
The truth is, when it comes to aromatic materials research, many times we learn just as much, if not more, from negative results.
Additional Research Problems
Another problem is the lack of the ability for real-life use, especially in regards to Aromatherapy. There are many studies that look real promising, but once you look at the specifics and see that they were done on mice, and they were using injections and/or unrealistic dosage amounts (for example 3g per kg), how does that translate to general Aromatherapy use? Also, was the oil used in vivo or in vitro? We can see certain things by in vitro tests like the antibacterial, antifungal, and antiviral properties of an oil, but there is so much in vitro testing cannot tell us in regards to real-world application.
Then, there is the added difficulty when using essential oils for their other properties, as they do not always work the same for everyone. For instance, Lavender (Lavandula angustifolia) can be very relaxing and helps some people sleep, but with others it has the opposite effect. So that leaves the question with smaller studies: did it really not work or did it just not work for these specific people?
There are also arguments by some critics that it is hard to definitively support anything with these types of studies. That animal studies are not the same as human studies, and while I have to agree there, they still have their uses. If nothing else, animal studies do show that the results are not just placebo and that essential oils and other plant extracts do have valid and visible therapeutic benefits.
In addition, there does seem to be an issue with proper controls in some studies. Some have also said that there is no way to do valid blind controls in humans since the oils have a scent. However, there are different ways to work around this depending on the situation. This is yet another reason why consulting with an expert would prove beneficial.
It is also important to remember that just because a study has been conducted, it does not mean that it is reliable. Is it repeatable and has it also been correctly peer reviewed by experts in the field?
Conflict of Interest and Funding
One of the biggest problems with conflict of interest (COI) is that there is much misunderstanding as to what exactly it means. In an attempt to gain more of an understanding, I contacted a place that stood out to me as an authority in this matter. Dr. Jessie Hawkins (via the International Journal of Professional Holistic Aromatherapy) graciously provided me with some information including the following on COI, stating that it is…
Technically, any situation where the author(s) have a financial or personal interest that could cause a reasonable person to have concerns that the author’s judgement may be compromised. Financial interests get the most attention but personal relationships are also considered conflicts. It does not have to actually influence the article, but if it gives the appearance of influencing the article, it’s a conflict. Technically, COIs can not be eliminated and they’re not necessarily bad things–unless they are hidden. Disclosing a COI doesn’t mean the author’s judgement has been compromised, simply that the authors have two interests which conflict. Whether or not the COI is sufficient to refuse to publish is entirely at your discretion and depends on the extent of the conflict.
The COI usually extends back about 3-5 years and for the ‘foreseeable future.’ So technically, all aromatherapists have a COI–it is in our best interest (both personally and financially) for EOs to work. But that’s not typically at the disclosure level.
The fact is, anything that could be considered COI should be submitted on a statement to the proper journal, etc. However, everything claimed on that statement may not be released to the general public.
The problem with these types of papers is not so much COI, but bias. One should remember that there is a difference between COI, bias, and perception of bias. Just because there is a COI does not mean there is bias, and one can have bias without COI. There is also the common problem of unconscious bias. More information on all of this can be found in the references below.
Sometimes COI presents in the form of funding. There is truly a lack of research on essential oils, but it is not because the science is not there to back them up, but rather because there is a lack of funds for research. Therefore, I do not have a problem with who funds a study as long as it is properly executed without bias. That being said, for many there will always be a perception of bias in certain cases, so there is a definite need for better options. However, where I do have a problem is when instead of studies being funded for the good of science and the aromatic community at large, they are funded to serve blatant conflicts of interests with bias that ensures they will not get taken seriously in the scientific community. These are, in my opinion, a waste of time and money that could have done some good otherwise. This is not even including the money that was also wasted on improperly done studies.
There are so many details that can affect the outcome of a study. I would like to see current guidelines and suggested protocol lists expanded and universally utilized across all types of aromatic materials research. I also suggest that if the people doing the research are not familiar with aromatherapy, that they do some sort of consulting or collaboration with a qualified aromatherapist and/or chemist in the field. This may prevent some common mistakes and make it so that the limited funds that are available for studies are put to much better use.
Also, because of many of the points already stated, and if for no other reason than general natural variation, the chemical constituents of the essential oils will always vary. Due to all these things, a proper analysis with an included GC/MS report may provide vital clues as to why a study did or did not end up with the expected results. In addition to that, it will have the added value of being useful to help find patterns when comparing to other studies.
Lastly, please remember to carefully review research papers as a whole as ALL the details matter.
I hope that in the very near future we will not only have many more studies done on aromatic materials, but also that they will all be performed to standards acceptable to the scientific, medical, and aromatherapy communities so they may be a great benefit for us all.
**Published in the International Journal of Professional Holistic Aromatherapy (IJPHA) Volume 8 Issue 4 Spring 2020
Since this article was originally published, steps toward improving issues with aromatic research have been taken. “TREATS (Transparent Reporting for Essential oil and Aroma Therapeutic Studies) was developed in response to poor reporting found during a systematic review that found many gaps in evidence-based studies and numerous omissions in reporting. This led to the formation of the 11-member international task force called ARQAT (Aromatic Research Quality Appraisal Taskforce) in January 2021. The group called on experts from around the world to determine items to be included.” To learn more please visit the ARQAT website. You can also listen to the interview with Marian Reven on the Aromatic Chat Podcast.
Aromatic Research Quality Appraisal Taskforce White Paper
“A Quest for Quality Reporting in Aromatic Research”
Special thanks to Lora Cantele, RA Editor/Publisher of the International Journal of Professional Holistic Aromatherapy (IJPHA) and Jessie Hawkins, PhD clinical researcher and Director of the Franklin Institute of Wellness, for assisting me with conflict of interest. Also, thank you everyone who read and gave input during the process of this article.
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Aromatherapy and Essential Oils: A Map of the Evidence
Prisma Transparent Reporting Of Systematic Reviews And Meta-Analyses
Aromatic Chat with Marni Reven
Aromatic Research Quality Appraisal Taskforce
Example of why you cannot always believe everything you read in a paper.
Alliance of International Aromatherapists (AIA) alliance-aromatherapists.org
Aromatherapy Registration Council (ARC) aromatherapycouncil.org
National Association for Holistic Aromatherapy (NAHA) https://naha.org/
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