Soothing Digestion with Essential Oils: Focus on Peppermint

Peppermint and Fennel Oils [replace all pepogest w/ peppermint oil EC
Fennel (Foeniculum Vulgare) which is commonly known as large, wild or sweet fennel, is described in herbal literature as possessing stomachic, carminative, pectoral, diuretric, diaphoretic and aromatic properties for medicinal use. Kloss (1994) describes fennel as a “thoroughly tried” remedy for gas, acid stomach, gout, cramps and colic. Ground fennel added to food has been demostrated to prevent gas in both the stomach and bowels and it has been proposed as a remedy for childhood bowel colic (Kloss, 1994). The essential oil of fennel has carminative qualities that are at least as effective as peppermint oil (Guenthes, 1949) and it is described as excellent for obesity treatment (Kloss, 1994). The effects of fennel in obesity are believed to be related to an appetite supressant effect but this area of efficacy remains underexplored.

Peppermint (Mentha piperita) is known in herbal, homeopathic and conventional medical practice to have aromatic, stimulant, stomachic, carminative, rubefacient and short lived local anestetic effects. Kloss (1994) describes peppermint as a excellent remedy for chills, colic, fevers, dizziness, flatulence, nausea, vomiting, diarihoea, dysentery, cholera, heart trouble, palpitations of the heart, influenza and even hysteria. In Russia and Eastern Europe peppermint derivatives have played a major role in the therapy of cardiovascular disease presumably because they exert an effect similar to widely used, cardiovascular prescription medication that blocks calcium entry into cells and effects cardiac and smooth muscle function. Peppermint containing products have enjoyed widespread use for the treatment of chest pain of cardiac origin, palpitations and gastrointestinal upset in Russia for several decades.

Of all of the known symptomatic benefits of peppermint and fennel, it is the carminative action of these compounds that is of special importance. Peppermint oil was standard symptomatic therapy of gastrointestinal upset in many hospitals worldwide prior to the introduction of several proprietary medications with alleged effects on adverse gastrointestinal symptoms. The introduction of prescription or over-the-counter “synthetic” medications for a variety of gastrointestinal symptoms has not been universally successful. Inhibition of acid with H2 receptor antogenists, such as Zantac, Tagamet, Pepcid and Axid, has revolutionised the treatment of significant acid related disease such as peptic ulcer and reflux esophagitis. However, these drugs are overutilised and it is known that more than 60% of the revenue derived from sale of these drugs by multinational pharmaceutical companies is as a direct consquence of the non-approved usage of these expensive drugs (Holt et al, 1991). These H2 receptor antagonists 5 have become available recently as over the counter medications and this circumstance could lead to even greater inappropriate use of these drugs.

Many gastrointestinal complaints occur in the absence of any serious underlying disorder and it makes sense to attempt to use natural based remedies which are inexpensive and safe as first line mangement for non-organic gastrointestinal complaints. It is often forgotten by many physicians that the first line therapy for irritable bowel syndrome is lifestyle and dietary change and the overuse of antispasmodic drugs with systemic side effects such as Librax and Bentyl should be avoided. Dietary adjustment with fiber is particularly important in the irritable bowel syndrome.

It is important to realise that drugs like Librax and Bentyl have not been shown to be any more effective in treating irritable bowel syndrome than carminative products in controlled trials. These are some of the reasons why natural based remedies such as peppermint and fennel are to be preferred as first line therapy for less serious gastrointestinal problems. Peppermint oil, especially enteric coated for maximum effective delivery, is well tolerated, inexpensive, of natural origin and it is devoid of systemic side effects or toxicity that may be present with some of the antisecretory medications (Zantac, Tagamet, Pepcid and Axid) or antispasmodic medications (Bentyl and Librax).

Mowrey (1986) in his book on the scientific validation of herbal medicines, indicates that peppermint and fennel contain volatile oils and other constituents that absorb intestinal gas, calm upset stomach, inhibit diairhoea and constipation, aid digestion and prevent or remedy childhood colic. Two distinct ways in which peppermint relieves gastrointestinal problems have been described by Mowrey 1986. These relate to resolution of biliary function and the normalisation of intestinal activity. Essential oils facilitate biliary function by stimulating contractile activity in the gallbladder, thereby allowing free flow of bile (List and Hoerhammer, 1968). Demling et al (1969) have drawn attention to the ability of peppermint oil to normalise gastrointestinal motor activity with the relief of both spasm and flaccidity in the intestines.

Peppermint oil has been found to inhibit several microorganisms, that according to Mowrey (1986), could cause digestive problems (Mowrey, 1986). The following microorganisms have been reported to be inhibited or inactivated by peppermint oil: Influenza A virus, Herpes simplex, Mumps virus, Streptococcus pyogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans (Sanyal and Varma, 1969, Herrman and Kucera, 1967, Abdullin, 1962, Pizsolitto et al, 1975, Maruzella and Sicurella, 1960, Maruzella and Lichtenstein, 1956, Tanner and Davis, 1922).

Mowrey (1986) states that “more than 30 pathogenic microorganisms have yielded to the influence of peppermint”. The role of essential oils, such as peppermint and fennel, as treatment or preventive agents for infection of the gastrointestinal tract requires further investigation. The broad antimicrobial action of pepermint lead to possible uses in supressing enteric microbes in several conditions including: travellers diarrhoea, opportunistic infection of the gastrointestinal tract in the patient with HIV disease (AIDS/ARC). Peppermint oil may be inhibitory against Helicobacter pylori which is the most important cause of acid related disease. Mowrey (1986) reviews the research of Maksimenko (1964) and Pasechnik 1966, where choleretic, antiulcer and antiflamatory properties of peppermint are proposed. If peppermint oil has an anti-ulcer effect it is possible that it exerts this effect by interference with the growth of Helicobacter pylori which is the key focus of current treatment regimens to cure peptic ulcer disease.

Fennel contains aromatic or essential oils that are very similiar in chemical structure and biological effects to those of peppermint oil (Shipochliev, 1968, Ramadan et al 1972, Mowrey 1986, Kloss, 1994). Fennel was listed officially in the U.S. Pharmacopoeia for many years and it is still officially recognised for its medicinal properties in more than twelve foreign pharmacopoeias worldwide (Mowrey, 1986). It is of interest that fennel is believed to assist in the promotion of weight loss by a presumed appetite supressant effect (Mowrey, 1986).

Plant terpenes have been used as combination therapy in a preparation named Rowachol® that was developed in Europe. Rowachol® has been shown to assist in dissolving gallstones in several studies and the effect of the combination of plant terpenes appears to be enhanced when combined with bile acid therapy (Werbach and Murray, 1994). Rowachol® contains the following in each 100mg capsule: menthol 32mg, menthone 6mg, pinene 17mg, borned 5mg, camphene 5mg, cineol 2mg and olive oil 33mg. Studies of the effect of plant terpenes on gallstones with or without bile acid dissolution therapy have been published by Sommerville et al, 1985, Ellis et al 1984, Bell et al, 1982, Handelsman et al, 1982, Ellis et al, 1981, Doran et al, 1979, Bell and Doran, 1979 and Hordinsky, 1971. Werbach and Murray (1994) state that enteric coated peppermint oil may produce similar effects to Rowachol® on biliary function but no conclusive data have been published on a gallstone dissolution effect of peppermint oil. However, peppermint oil (which contains Menthol 42%, Menthone 27%, Neo-menthone 7%, Cineole 6% and Menthyl acetate 6% in approximate quantities) is known to produce a spasmolytic effect on the sphincter of Oddi and it promotes the release of cholecystokinin in animals (Giachetti et al, 1988).


Plant essential oils that are derived from peppermint, dill ,caraway and fennel have been known for many centuries to have beneficial properties in relieving of variety of gastrointestinal symptoms (Guenther, 1949). It is the cyclical mono-terpene content of essential oils that is believed to exert several beneficial pharmacological effects which include inhibition of gastrointestinal smooth muscle function, with resultant antispasmodic properties (Gunn, 1920, Plant and Miller, 1972, White et al,1987, Duthie, 1981). Peppermint oil has been used in variety of formulations to treat symptoms such as functionaldyspepsia, abdominal colic, postoperative abdominal pain and the troublesome manifestations of the irritable bowel syndrome (Creamer, 1955, Sigmund and McNally,1969, Somerville et al, 1984, Harries et al, 1978, White et al, 1987, Meyrick Thomas et al, 1988, Dew et al, 1984).

Carminative effects of Peppermint and Other Essential Oils
These essential oils have a documented carminative effect. The term “carminative” was coined to describe the overall effect of several aromatic essential oils on digestive function. Peppermint oil is anexample of an essential oil that has very specific effects in the relief of flatulence and associated dyspepticcomplaints (Martindale,1989).Peppermint oil contains menthol, which is a cyclical mono-terpene that israpidly absorbed from upper portions of small intestine when taken by the oral route. Since the action of essential oils, including peppermint oil, occur almost exclusively on a local basis it is often necessary to deliver the carminative preparation in a delayed-release formulation, if effects are required in the lowerportions of the intestines (White et al, 1987).

The carminative effect of essential oils, such as peppermint, has been linked to the relief of flatulence (Martindale,1989). The mechanism whereby flatulence is relieved is not entirely understood, but it is related perhaps to a local stimulatory effect of essential oils on the gastrointestinal tract. This timulatory effect is frequently followed by a mild degree of local anesthesia (Martindale,1989). In particular, essential oils are believed to be quite useful in the therapy of gastric bloating. Gastric bloating may be associated with disturbance of upper gastrointestinal motor function, but the relationship between disordered gastric emptying and functional dyspepsia remains ill-defined (Holt, 1990). It is commonly observed that the relief of abdominal bloating is frequently associated with eructation or belching of gas and in the case of lower abdominal distention relief is often associated with the passage of flatus. It has been proposed that the passage of gas from the upper or lower digestive tract is facilitated by the breaking up the foam that may form in the lumen of the gastrointestinal tract. In addition, essential oils may reverse spasm of the bowel that is associated with gaseous distention, and they may assist assist in The carminative effect of essential oils, such as peppermint, has been linked the expulsion of gastrointestinal gases.

Effects of essential oils on gastrointestinal function. Essential oils such as peppermint oil when instilled into the large bowel have been shown to reduce colonic motility (Duthie,1981) and spastic intestinal contractions (Leicester and Hunt, 1982). Is believed that many of the symptoms of functional gastrointestinal disorders, including irritable bowel syndrome or gastroparesis arise from alterations in gastrointestinal motor function. Studies have shown altered colonic motility in irritable bowel syndrome (Holdstock et al,1969 and Sullivan et al,1978). Well-conducted clinical experiments have indicated that the administration of peppermint oil by the oral route results in a decrease in lower esophageal sphincter pressure (Creamer 1955, Sigmund and McNally, 1969). This effect occurs within 1 to 15 min post administration of peppermint oil, but lasts only for approximately 5 min (Creamer,1955 ,Sigmund and McNally,1969). When 0.2 ml of peppermint oil placed directly into the lumen of colon,inhibition of colonic motor activity occurs within a couple of minutes and effect lasts approximately 12 min (Duthie, 1981).

Mechanism of Action of Essential Oils on Gastrointestinal Function
The mechanism of action of carminative oils involves several physiological changes, including anti-foam action, an antispasmodic effect and a local anesthetic effect. The effects of essential oils are localized in the gastrointestinal tract. In contrast to other antispasmodic medications that are used to treat functional gastrointestinal disturbance, peppermint exerts a local effect where as synthethic compounds exert pharmacological effects as a consequence of their systemic bioavailability. Mebeverine exerts a “papaverine- like” effect and dicyclomine exerts an “atropine-like” effect, but unlike essential oils, these effects are not confined to the gastrointestinal tract. The general systemic effects of antispasmodic medications such as mebeverine or dicyclomine may limit their use because of systemic pharmacological effects which may result in adverse drug reactions.

There is a difficulty in the study of the pharmacodynamic effects of essential oils, because theactive constituents of the oils, namely the mono-terpenes, are rapidly and completely metabolized following their prompt absorption from the upper gastrointestinal tract. Pharmacokinetic studies of the mono-terpene contents of peppermint (menthol) use indirect assay methods because of the rapid elimination of conjugated menthol in the urine. Menthol is excreted as glucuronide conjugate in urine.

It has been hypothesized that carminative effect of essential oils may be related to their action on intestinal foam. Peppermint, fennel, cinnamon, orange, dill and caraway oils have been shown to be highly effective in disrupting of gastrointestinal foam as a consequence perhaps of the stimulation of gastric and intestinal secretion (Harries et al, 1978). Foam is generally found in the upper gastrointestinal tract and it is not perceived to be generally a problem in the large intestine. It is believed that the disruption ofthe bubbles in gastrointestinal foam may lead to a collapse of the foam resulting in the release of gas that can then be passed by eructation or the passage of flatus. The build up of foam and its retention in the lumen of the gastrointestinal is believed to give rise to discomfort and intestinal spasm and colic (Harrieset al, 1978). This buildup may give rise to dyspepsia or lower abdominal pain. It has been well recognized that anti-foaming agents are useful in the facilitation of the passage gas from the gastrointestinal tract and they are associated with general relief of the symptoms of functional gastrointestinal disease.

There are at least two components that may contribute to the action of essential oils in the relief of the spasmodic contractions in the tubular-digestive tract. Essential oils exert a local anesthetic effect which may be related to change in the membranes of sensory cells that may react with the lipophilic essential oil. This local anesthetic effect has been postulated to contribute to the interruption of the cycle of the gastrointestinal irritation which may precipitate spasm through intrinsic reflexes in the gastrointestinal tract.

Essential oils, such as peppermint and fennel oil, can be demonstrated to exert a significant smooth muscle relaxant effect which is believed to relate to inhibition of calcium channels (Taylor et al,1985). Peppermint oil and menthol alone are known to block the carbachol (achetylcholine-like) induced influx of calcium ions into cells. Thus, essential oils appear to be calcium channel blockers and exert pharmacological effects similar to those observed with current prescription medications such as nifedepine or diltiazem, which are calcium channel antagonists. Calcium channel blocking drugs, such as nifedepine or diltiazem, are known to exert effects on upper gastrointestinal motor function, including inhibition of esophageal peristalsis, and a reduction of the lower esophageal sphincter pressure, in the absence of major effects on gastric motor function (Blackwell et al, 1981).

Clinical Studies of Essential Oils
Several clinical studies have shown the beneficial effects of essential oils, especially peppermint oil, on a variety of gastrointestinal disorders (Rees et al,1979, Dew,1981, Evans et al,1982, Meyrick Thomas,1986). Rees et al (1979) undertook a double blind crossover trial of the effects of peppermint oil on the relief of symptoms in the irritable bowel syndrome. In this multicenter study, there was a significant improvement in the relief of symptoms of the irritable bowel syndrome compared to placebo.These results were confirmed in a further multicenter trial, performed by Dew et al (1979), where 29 patients from 7 hospital centers entered into double -blind crossover study to examine the effects of peppermint oil on symptoms of irritable bowel syndrome. In this study, patients received either encapsulated peppermint oil or placebo capsules and during each treatment period of two weeks the patients were requested to record the severity of abdominal symptoms, stool frequency and side effects of the medication on a daily basis.

The overall assessment of the patients showed that they felt significantly improved while taking peppermint oil capsules compared with placebo and the subjects considered peppermint oil to be better than placebo in relieving abdominal symptoms. Patients who received peppermint oil had a much lower daily symptom score, than those receiving placebo, but no demonstrable effect occurred on the number of daily bowel actions. It was concluded by Dew et al (1984) that peppermint oil was a potent agent for the relaxation of gastrointestinal smooth muscle.This latter study confirmed the earlier findings of Rees et al (1979) and showed the benefit of peppermint oil in treatment of irritable bowel syndrome in a multicenter, controlled clinical trial.

Meyrick-Thomas et al (1988) undertook a double-blind clinical trial which compared peppermint oil and placebo in the prevention of abdominal pain, distention or colic following appendectomy. This small clinical trial showed a benefit for peppermint oil in reduction of postoperative pain, but this study was complicated by problems that occurred in the investigation of the prevention of the symptom which effects a small and unpredictable minority of patients postoperatively (Meyrick-Thomas et al, 1988). However, Meyrick-Thomas et al (1988) concluded that peppermint oil may prove useful for the prophylaxis of postoperative pain if groups of patients at high risk of postoperative pain could be identified.

Other uses of essential oils have been proposed, including the relief of spasm during endoscopy of the gastrointestinal tract, especially for the relief of spasm during colonoscopy. Equally, other maneuvers that may induce spasm may be amenable to pretreatment with essential oils, such as the application of essential oil prior to administration of colonic washouts or enemas. Peppermint and fennel oil are useful adjunts to the toleration of colenic washout programs.

McKenzie and Gallacher (1989) reported a successful use of peppermint oil for assisting patients with their acceptance of a colostomy. These authors pointed out the problems that patients experienced with odor that occurs from a colostomy. McKenzie and Gallacher (1989) found that peppermint oil in enteric coated capsule was highly effective in masking the fecal odor that was a common problem for patients with a colostomy. In this study , 14 of the 20 patients found that odor from their colostomy was improved, and 15 of the 20 colostomy patients found their colostomy much more acceptable. It was noted in this patient group that the consistency of fecal matter in the colostomy and frequency of bag changing appeared to be improved.

Development of a Carminative Product: Enteric Coated Peppermint Oils
Several preparations of delayed-release peppermint oil have been formulated. Two of these preparations: Colpermin (Tillotts Laboratories) and Mintech (Smith- Klein-Beecham) have undergone successful use and clinical trial. Available preparations of peppermint oil have disadvantages or limitations. First, other highly potent cyclical mono-terpenes exist in a variety of other plant products which have not been incorporated into existing formulations. Of available essential oils, the author has had particular success with the recommendation of fennel oil as a carminative. This together with other factors such as pharmaceutical formulation have resulted in the development of the new natural product that is highly effective in modulating gastrointestinal motor function. This new product,

The essential oils in this preparation are released from delayed-release capsules, which are coated with hydrophobic excipient. The presentation of the essential oils in this formulation results in a prolonged delivery of essential oils to the gastrointestinal tract in the middle to distal small intestine and colon. The resulting release of essential oils from Pepogesttm in the lower intestines is quite desirable in the control of the symptoms of the irritable bowel syndrome.

Peppermint Oil EC is a carminative preparation that contains essential oils in a delayed-release formulation. The carminative effect of Peppermint Oil EC is related to its anti foaming properties and the antispasmodic effects of essential oils, which have been demonstrated in earlier studies (Somerville et al, 1984, Harries et al, 1978, Taylor et al, 1985). The antispasmodic effects of the essential oils are most desirable in lower small intestine and colon and since the essential oils work by a local mechanism. The delayed delivery system of the essential oils in the gastrointestinal tract is one of the keys to the successful use of Peppermint oils.

It is recommended that Peppermint Oil EC TM be taken approximately 20 min prior to meals, so that the entire capsule may be emptied through a relaxed pylorus during the process of gastric digestion. The capsule will be emptied from the stomach in this state by the migrating motor (“housekeeper”) complex of elctromechanical activity in the bowel. Essential oils are very safe and they are ubiquitous in foods. Peppermint is used as a flavoring in a variety of beverages and foods. No systemic toxicity of peppermint oil or fennel oil is known despite many years of use of these natural agents.

Peppermint can reduce the lower esophageal sphincter pressure, and on occasion patients who have gastroesophageal reflux as a consequence of low esophageal sphincter pressure, may have a short-lived exacerbation of their reflux symptoms. This may result in minor, short lived heartburn or acid reflux. This side effect may occasionally lead to discontinuation of the medication,but the effects on lower esophageal function only last about 15 min. There are no known local or systemic toxicities of essential oils when taken in recommended therapeutic dose.

Overall, Peppermint Oil EC™ provides a highly attractive option for the patients with functional gastrointestinal symptoms that are generated by gas and spasm or colic in the digestive tract. Peppermint Oil EC™ proves effective for the relief of upper and lower digestive complaints that may be related to abnormal motor function of the gastrointestinal tract.

The specific target populations for the use of Peppermint Oil EC™ are: patients with intestinal gas, spasm, colic, dyspepsia from colic, altered bowel habit with the irritable bowel syndrome, colostomy patients and individuals undergoing instrumentation of the gastrointestinal tract such as lower endoscopy, enema administraion, detoxification programs using colonic washouts and contrast radiology of the lower gastrointestinal tract, such as barium enema examination.

Enteric-coated hard gelatine capsule size 1 with red band between cap and body. Each capsule contains 0.2ml peppermint oil and 0.1ml fennel oil.

For the treatment of symptoms of discomfort and of abdominal colic and distension experienced by patients with functional gastrointestinal disease, especially irritable bowel syndrome. For colostomy patients and those undergoing interventions of the lower gastrointestinal tract where oral therapy is convinient.

Dosage and Administration
For oral administration

Adult dose
One capsule to be taken three times per day, taken 30-60 min. before food with a small quantity of water. The capsules should not be taken immediately after food. The dose may be increased to two capsules three times per day when discomfort is more severe. The capsules should be taken until symptoms resolve. Persistent symptoms should be reported to a physician.

Dosage for the elderly
The mode of action of peppermint and fennel oil are local rather than systemic. Clinical experience has not necessitated alternative advice for elderly patients. The product enteric coated peppermint oil is not recommended for children under the age of 15 years or during pregnancy.

Contraindications, warnings, etc.
Precautions: The capsule should be swallowed whole. The capsule should not be broken or chewed because this would release the pepperiment oil and fennel oil prematurely. This could possibly result in local irritation of the mouth and esophagus. Patients who have heartburn as a prominent symptom sometimes experience an exacerbation of thesesymptoms when taking Peppermint Oil EC™. Usage should be discontinued if heartburn occurs. Antacid should not be given at the same time as Peppermint Oil EC™.

Adverse Effects
Occasionally heartburn, or a slight burning sensation in the anal passage. Allergic reactions to peppermint and fennel are rare but, as with natural medicaments, can include red skin rashes, headache, slow heart rate, muscle tremor and dizziness.

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