Oregano Oil Research
Science was never one of my strengths. I certainly never imagined myself becoming immersed in microbiology. But that is what happened, and it turned out to be one of the most fascinating parts of the project.
Over a period of about four years we worked closely with microbiologists at SGS in Delhi and at the University of the West of England (UWE) to understand the properties and potential health applications of Himalayan oregano oil. The purpose of the research was to work out how we could transform the wild oregano from ‘useless grass’ into a high-value product, ultimately enabling us to pay a premium price to the herb collectors.
For those who wish to skip the details, here are the main conclusions of our research:
- Himalayan Oregano oil has powerful antimicrobial properties, effective against gram-positive and gram-negative bacteria, fungus, yeasts and mold.
- The carvacrol and thymol content appears to be highly variable, which suggests that it may not be suitable for internal use.
- Himalayan oregano oil is fast-acting; 90% of the bacteria is killed in the first minute of application.
- Its vapour has powerful antimicrobial properties, which means that it could be used to treat areas that are hard to reach (such as the back of the nose).
- Unlike many antimicrobials, oregano oil is heat resistant, which could be an advantage in many healthcare settings.
- Himalayan oregano oil is quite evenly matched with tea tree oil and Mediterranean oregano oil.
- The only oil that we tested that was (marginally) more effective than Himalayan oregano against MRSA was a thyme oil from south India, although the oregano oil was still more effective at very low concentrations.
Some of these results have been published in a paper titled Efficacy of oregano oil as a biocide agent against pathogens in vitro, using lux reporter gene technology, written by Nahla Eltai, a PhD student at UWE. Download here or in sidebar.
Below I have done my best to summarise the details of the research done by SGS and UWE in layman’s terms that make sense to me:
Research #1: Carvacrol and Thymol Content
According to most literature, carvacrol is the primary indicator of the antimicrobial and therapeutic properties of oregano oil. It is said to be non-toxic and can be safely consumed internally to treat a variety of health issues. Many varieties of oregano also contain thymol, a compound also known for its antimicrobial properties but said to be toxic to the liver if taken internally.
So the first area of research we focused on was to assess the carvacrol content of different batches of oregano oil harvested at four week intervals in 2007. Our initial results were very encouraging; the two samples that were harvested during the main collection period (July and August) had a carvacrol content of 78.25% and 72.64% respectively. We had also purchased some high-grade Mediterranean oregano oil as a benchmark, which came back with a carvacrol content of 75%.
Strangely though, we were never able to replicate the results of 2007. The following year, we had incredibly varied results ranging from 1.6% to 67%. We also started testing for the thymol content and found that some batches contained up to 50%. To add further confusion, we re-tested various batches and found that within a year the carvacrol content dropped to as little as 3.1%.
When we started working with UWE in 2008, we re-tested several of the same batches that we had given to SGS to see whether the fluctuating results had anything to do with the methodology, but their results were more or less the same. In short, we found that there was massive variation and were unable to form any conclusions over the carvacrol and thymol content of Himalayan Oregano oil.
This raised questions over whether it was safe to consume it internally as we had originally assumed. I have often taken it myself, and others have reported excellent results from taking it internally. But with these results, to be on the safe side, we decided that we should focus on researching the external uses of the oil, i.e. sprays, wipes, creams, and dropped any thoughts of marketing it for internal consumption.
Research #2: The Biochemistry of Oregano’s Antimicrobial Properties
One thing we did prove without was that the Himalayan oregano oil has very powerful antibacterial and antifungal properties, and that the carvacrol content appears to make only a marginal difference to its efficacy.
Research done by UWE showed that in tests against E. coli, S. aureus & P. aeruginosa the most effective batch had a carvacrol content of just 1.96% and a thymol content of 36.93%. In other experiments by SGS the best results came from batches with high carvacrol and low thymol; the net results appeared to be more or less the same regardless of the ratio of these two key components.
Interestingly, UWE found that the most potent batch of oregano oil was more effective than the purified carvacrol or thymol in isolation. This suggests, as we suspected, that its antimicrobial properties are far more than carvacrol and/or thymol; there are likely to be many other compounds all working synergistically to create its overall effect.
One of the reasons we chose to focus on antibiotic-resistant bacteria is because this synergistic action makes it much harder for the bacteria to develop resistance against. The antimicrobial properties found in plants such as oregano are a result of many millennia of their own evolutionary arms race against microbial invaders.
One of the differences between plants and humans is that plants appear to have no desire or need to patent their products or comply with EU legislation, and therefore produce highly complex and variable active ingredients, which help prevent microbes from develop resistance. We, on the other hand, have created a regulatory system in which identical synthetic compounds are mass-produced at a deceptively low cost. To me, this does not bode well for our own evolutionary arms race against the superbugs.
Research #3: Himalayan Oregano against MRSA and other bacteria/molds
Research by SGS showed that the Himalayan oregano oil eliminated MRSA in dilutions of 1 in 1000 and was more effective than all of the 18 other antimicrobial agents it was compared against. The results showed that it has bactericidal rather than just bacteriostatic properties (in other words it kills bacteria rather than just inhibits growth), which means that it would be ideal for cleaning hands or wiping surfaces in hospitals.
Between UWE and SGS they showed that the oregano oil was very effective against MRSA, S. aureus, E .coli, E. sakazaakii, A.niger and to a lesser extent against C. albicans. They both found that MRSA and S. aureus were equally affected by the oregano oil. There were some conflicting results against Pseudomonas aeruginosa; UWE showed that oregano oil was effective, whereas an SGS experiment showed that it had no effect.
Research #4: Rate of bactericidal activity
One of the most pioneering areas of UWE’s research was that they were able to measure exactly how long it took for the oregano to eradicate MSSA (methicillin sensitive S. aureus). They did this using glowing bacteria and a very sensitive light meter, otherwise known as ‘lux reporter gene technology’.
Using this technology, they were able to demonstrate that the oregano oil is fast-acting; against E. coli, P. aeruginosa and MSSA it reduced 90% of the bacteria in the first minute of application. After this initial reduction the rate of eradication slowed down, and it took 15 minutes for 99% to be killed.
Research #5: The Antimicrobial Efficacy of Vapour
One of the unique advantages of using essential oils rather than conventional chemicals is that they produce vapour that also have antimicrobial properties. Research done by UWE showed that oregano oil vapour produced at 37’C eradicated MRSA at a distance of 1cm, and inhibited repeat populations over 24 hours later. This means that it could potentially be used to disinfect areas that would otherwise be hard to reach – for example, an MRSA infection at the back of the nose or to treat lung infections.
Research #6: Heat Stability
Another unique advantage of using essential oils over conventional chemicals is that many are heat stable. This was verified by UWE who heated the oregano oil up to 100’C for 10 mins, and the result was an unaltered zone of inhibition with MRSA. This could be another big advantage over most chemicals/antibiotics, which are usually heat labile (i.e. liable to change), and could be used in applications such as laundry powder, which need to be heated.
Research #7: Oregano Oil vs Other Antimicrobial Essential Oils
Out of curiosity we did a few tests to compare Himalayan oregano oil with other essential oils, including tea tree, thyme oil and our own wild collected juniper oil. The oregano turned out to be quite evenly matched with the tea tree oil; it was more effective against MRSA and Yeast, but the tea tree came top against E-coli and mold.
The juniper oil had some effect at much higher concentrations, but otherwise wasn’t in the same league as oregano. But interestingly, thyme oil that was produced in south India turned out to be more effective than oregano at higher concentrations, but not as effective as oregano at very low concentrations.
Wish-list for further research:
- Further GCMS studies to understand the variations in carvacrol / thymol content, and how this affects antimicrobial efficacy.
- Toxicity tests to verify whether Himalayan oregano oil with high thymol content can be consumed internally.
- Testing of finished products (sprays, creams etc.)
- Organic seed treatment