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References (for Parts 1 and 2 .pdf) were not in our print edition.
Editor note: Part 1 of this article, published in December 2018, discusses issues of safety, essential oil quality, metabolism, and synergy when using essential oils orally. Part 2 looks at the clinical application of ingested essential oils for intestinal discomfort.
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Preliminary Considerations
Before selecting a therapeutic modality of any kind, it is important to address the underlying cause and use a naturopathic and functional medicine approach to address it. I would be amiss to not briefly review some preliminary considerations for using essential oils.
For intestinal discomfort and symptoms, an integrative doctor will want to take a full history, perform a physical exam, and run the appropriate tests. Examples of laboratory assessments include imaging for detecting pathology and functional issues, assimilation and absorption markers (e.g., pancreatic elastase, products of protein breakdown, fecal fats), excess inflammatory indicators (e.g., calprotectin, eosinophil protein X (EPX), lactoferrin), a Celiac panel, SIBO breath test, markers for bacterial, viral, fungal, and parasitic overgrowth, and microbiota panels.
A "Five R" program for restoring and healing a diseased gastrointestinal tract is the preferred protocol in functional medicine, but the aspects are likely be implemented by most integrative practitioners. These Five R's are the following:
- Removing the cause and contributors (i.e., dietary, microbes, or environmental),
- Replacing the nutrients that are needed for assimilation and digestion,
- Repairing the damage to the gut,
- Re-inoculating the good bacteria, and
- Rebalancing lifestyle factors (sleep, stress, exercise) that can perpetuate a dysfunctional gut.122-124
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Oral Use of Essential Oils for Intestinal Discomfort
Now, I will start the discussion on the "nuts and bolts" of internal administration of essential oils for gut discomfort. I will review the evidence in the research for the use of the most common essential oils for intestinal health and those that I personally use in my practice. I will also provide dosages, if available, that are recommended from scientific reviews and experts. Next, I will give a summary on essential oils' antimicrobial effects and their impact on the microbiome. Finally, I will give a synopsis of how I would incorporate these essential oils in my practice.
Despite the controversary surrounding oral application of essential oils, many practitioners are already currently administrating two essential oils for gut comfort without concern. Many practitioners who run the previously mentioned lab markers have witnessed that certain essential oils are deemed "sensitive" to dysbiosis markers on various functional gastrointestinal health panels. For this reason, many functional and naturopathic medicine practitioners have experience administering the essential oils of oregano for its antimicrobial properties124-127 and enteric coated peppermint oil for irritable bowels.128-132 Two additional essential oils I personally use in my practice are fennel and ginger. Please refer back to the previous section on "Internal Usage of Essential Oils: Controversy, Scare Tactics, and Bad Science" in which I highlighted the benefits of fennel oil for gut distress and its safe internal use. There is also one proprietary blend I have found to be very clinically effective.
 Peppermint Oil
Peppermint is perhaps the most researched and clinically evaluated essential oil used for intestinal discomfort. It has even been validated in several trials for its efficacy in IBS subjects.128-131
Peppermint's mechanism of action on pain has been studied but is not conclusive. It may be related its impact on TRPM8, a transient receptor potential (TRP) cation channel. This receptor has been found to be activated by cold temperatures and menthol, a main constituent found in peppermint essential oil. It induces smooth muscle contractions inversely relational to stimulation (temperature) and initiation of Rho-kinase. This leads to smooth muscle contraction. Furthermore, there is some controversial evidence that menthol modulates intracellular calcium stores. In summary, peppermint oil may relieve intestinal discomfort through activation of TRPM, modulating calcium stores, and stimulation of menthol.129
There is a safety precaution reported in the literature that peppermint may delay gallbladder emptying. The evidence cited for this is based on one study of 12 healthy volunteers that was assessing gastrointestinal motality.128,130-131
In this experiment, the researchers compared the effects of a combination of 90 mg of peppermint oil in 50 mg of caraway oil to a proprietary formulation to two medications and a placebo that contained NaCl (salt). The participants were tested at baseline and after drinking apple juice at various time intervals. The authors simultaneously measured gastric and gall-bladder emptying ultrasonically and orocaecal transit time using the H2 breath test using lactulose.128 The authors concluded the following:
Further investigations need to be conducted to study the effect of peppermint oil and caraway oil on a maximal contraction stimulus on the gall-bladder (e.g.after a fatty meal), to investigate the effect of a combination of both oils (as found in a number of herbal drugs) and to examine whether the pharmaco-dynamic effects can also be shown in patients suffering from motility disorders.128
I take issue to making this safety flag for peppermint oil based on twelve healthy volunteers. Under normal conditions, fatty acids stimulate gallbladder contraction. The test drink was a non-fat juice, so how could the gallbladder be stimulated? Still, according to the Expanded Commission E, the following contraindications are reported: "Obstruction of bile ducts, gallbladder inflammation, severe liver damage. In case of gallstones, to be used only after consultation with a physician. Preparations containing peppermint oil should not be used on the face, particularly the nose, of infants and small children."132
I believe that due to the impressive clinical trials that report the efficacy of peppermint for IBS, it may be a better conclusion that it is a modulator of digestive function rather than an inhibitor or stimulator of motility. Furthermore, with appropriate dosage, clinicians should not dismiss this essential oil for fear of harm.
Oregano Essential Oil
Whereas ingestion of peppermint oil has many clinical trials of efficacy for assisting with digestive distress, oregano oil does not. Yet, it is one of the go-to essential oils for most practitioners in treating gut discomfort related to microbial imbalances. Interestingly, clinical trials on efficacy regarding the popular use for intestinal dysbiosis is lacking.133,134 There is one lone study on inhibition of enteric parasites.125
Its isolated compound, carvacrol, was found in vivo to have protective effects against clostridium difficile associated dirrahea.135 In another in vivo model using pigs, oregano oil was found to improve intestinal permeability via modulating bacteria and immune status. Interestingly, the oregano oil used, as reported in the analysis found within the supplementary materials, did not contain the two components considered to be most active.136 Many manufactured oregano oil products are encapsulated and standardized to carvacrol and thymol.
Still, clinicians report benefits and improvements of markers of intestinal dysbiosis for their patients.
As far as safety, it is recommended to be diluted in a fatty oil due to its potentially corrosive properties.
Ginger Essential Oil
Ginger is another well-known herb for its digestive properties and alleviating discomfort. It has evidence of this from a few human trials and many in vitro and in vivo.137-142 In vitro and vivo, ginger oil has been shown to be microbe inhibiting and have inflammatory modulating properties. The constituents of ginger oil have also shown to be stomach protective,139 possess antioxidant properties, and modulate inflammation.137-142
One study review of five trials had compelling evidence that the inhalation of a combination of peppermint oil and ginger oil could assist with nausea, though some methodical issues were reported. The authors stated, "Their results suggest that the inhaled vapor of peppermint or ginger essential oils not only reduced the incidence and severity of nausea and vomiting but also decreased antiemetic requirements and consequently improved patient satisfaction."142
Cumin Essential Oil
Cumin essential oil is another essential oil traditionally used for digestive health. A small pilot trial with 57 subjects diagnosed with IBS using ROME II criteria assessed the efficacy of 2% cumin essential oil and had an impressive outcome. The essential oil was administered as 10 drops twice daily for four weeks. The authors concluded, "Abdominal pain, bloating, incomplete defecation, fecal urgency and presence of mucus discharge in stool were statistically significant decreased during and after treatment with Cumin extract. Stool consistency and defecation frequency were also both statistically significant improved in patients with constipation dominant pattern of IBS."143
Proprietary Formation
I have had success using combinations of essential oils in proprietary formulations for intestinal health promotion and relief of irritation. One essential oil blend I routinely use contains the following single oils with evidence of digestive support: Artemisia dracunculus (tarragon) oil,144 Zingiber officinale (ginger) root oil,137-142 Mentha piperita (peppermint) oil,128-132 Juniperus osteosperma (juniper) oil,145 Foeniculum vulgare (fennel) oil,110-114 Cymbopogon flexuosus (lemongrass) oil,146-149 Pimpinella anisum (anise) seed oil,150 and Pogostemon cablin (patchouli) oil.
This has been very effective in my practice for relief of gastrointestinal discomfort and symptoms. Most report improvement within one month. This is likely due to the synergistic components of the essential oils.77-78
Dilution and Dosages: A Guide for Essential Oils
Now that I've reviewed the evidence that ingesting essential oils and that their use for intestinal discomfort is science-based, I will now discuss specific dosage guidelines. Although aromatherapists have different viewpoints on dilution amounts necessary for safe application, measurement for what constituents a single dose is a commonality.
In this section, I will provide a dosage guide compiled from the experience of experts and various merchandizers.**
Most essential oils come in 5 ml and 10 ml bottles. This equates to approximately 100 and 300 drops respectively. A general knowledge of equivalency from drops to measurements is necessary for the practitioner to understand, as most often dosage is based on drops rather than liquid measurements of essential oils. Please see Table 1 for these conversions and dilutions of essential oils (EOs).117-121
Table 1: Essential Oils Conversion and Measurement Chart
1 oz. = 30 ml
1 oz. = 600 drops essential oils
1 oz. = 2 Tbsp. or 6 tsp.
Using these conversions:
6 drops of EO per oz. of carrier oil = 1% dilution (1% of 600 drops)
3 drops of EO per Tbsp. or 3 tsp. = 1% dilution (1% of 300 drops)
1 drop of EO per tsp. = 1% dilution
1 drop of essential oil = approximately 0.02 to 0.03 grams = 20-30 milligrams = 20000 micrograms (µg)
30 mg = approximately 1 drop*
*Compiled from references 117-121
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