Peppermint leaves

Mentha piperita comes from the Greek, Mintha, the name of a mythological nymph who transformed into the plant, and the Latin, piper, which means pepper. Peppermint is a hybrid of two different plants: spearmint and water mint.

Throughout the ages, people have used peppermint for culinary and medicinal purposes. Excavation of ancient Egyptian tombs revealed evidence of peppermint use. The Greeks and Romans both used it as a flavouring agent and in tea and wine. Although peppermint has a long history of therapeutic use in many cultures, it is only since the 18th century that western European medicine accepted its general use.



Peppermint tea, a water infusion, is a widely used soothing beverage made by pouring hot water over the fresh or dried peppermint leaves.

To extract the peppermint oil in the form most studied in the medical literature concerning gastrointestinal (GI) conditions, the stems, leaves, and flowers are steam distilled. The resulting oil is generally available in enteric coated capsules, gelatine capsules, and in bulk liquid form.

Menthol, a derivative of peppermint, can be taken in the form of an inhalant and is frequently an ingredient in body rubs and liniments. Menthol has an anti-spasmodic and relaxing effect on the smooth muscles of the GI tract.


Present Use

There is good evidence for the use of peppermint oil in treating irritable bowel syndrome symptoms and for the combination of peppermint and caraway oils in treating functional dyspepsia.

Limited evidence suggests peppermint oil may be beneficial as an anti-spasmodic agent for use during and after endoscopic procedures and barium enemas.


Side Effects, Contraindications, Interactions

Peppermint is safe when consumed in small doses in tea, candy, or chewing gum, and when used in toothpastes or mouthwashes; however, peppermint may produce reactions such as heartburn, perianal burning, blurry vision, nausea, and/or vomiting if you consume too much.

Other side effects could include headache, dizziness, slow heart rate, and muscle tremor. In very large doses, peppermint oil can result in muscle weakness, brain damage, and seizure. When used externally, peppermint oil can cause skin rashes and other symptoms, such as mouth sores and eye irritation.

Health Canada advises consulting a healthcare practitioner before using peppermint for individuals with gallbladder or bile duct obstruction, hiatus hernia, or gastroesophageal reflux disease (GERD).

Pregnant and/or breastfeeding women should avoid peppermint oil and menthol due to insufficient information regarding its potential for toxicity. Studies in children have shown only mild side effects such as heartburn when taken orally and skin irritation when applied topically. Exercise caution, however, since products don’t always have the same effects in children as in adults.



Caraway Seeds

Caraway, or Carum carvi, a herb cultivated since ancient times, is native to Europe and western Asia and belongs to the parsley family. It is added to meats, cheese, bread, and sauerkraut, and used for flavouring alcoholic drinks such as aquavit.

Throughout Europe, many believed that if you added caraway to something, then no one could steal it from you. Therefore, lovers used caraway as a potion to keep others from stealing the objects of their affection and farmers often added caraway to feed to ensure their animals stayed nearby.



The caraway plant’s dried fruits (commonly called seeds) contain 3-7% essential oil. Caraway fruits can be made into an infusion, where the crushed fruits are allowed to steep in hot water, or the essential oil may be extracted and consumed in capsule form, typically in combination with other compounds.


Present Use

Caraway is used medicinally for its carminative (anti-gas, anti-flatulence, and anti-bloating), and anti-spasmodic properties; and to treat flatulent colic in infants. In addition, the essential oil of caraway fruit has shown antimicrobial properties against Escherichia coli, Staphylococcus aureus, Salmonella typhi, and Shigella dysentery. In combination with other oils, caraway oil can be effective in treating functional dyspepsia and irritable bowel syndrome, and it sweetens the breath.


Side Effects, Contraindications, Interactions

Those with sensitivities or allergies to celery or members of the plant families Umbelliferae (Apiaceae) and Compositae (Asteraceae), such as cumin, parsley, carrot, dill, and fennel should avoid caraway. Caraway oil may have a negative effect on the gallbladder and in heavy doses may cause liver damage. Women who are pregnant or breastfeeding should seek the advice of a physician before using caraway. Some people may experience dermatitis from contact with the essential oil.


Current Research

Functional Dyspepsia

This common condition, affecting 20-29% of Canadians, is usually self-managed with only a small number of patients seeking medical care. The disorder manifests in feelings of pain, premature fullness as well as bloating, nausea, and sometimes vomiting. A number of studies have looked at a combination of peppermint and caraway oils as a remedy for functional dyspepsia. One double-blind placebo-controlled study showed a greater reduction in pain intensity (40% vs. 22% with placebo), and sensation of pressure, heaviness, and fullness (44% vs. 22% with placebo). Additionally, in terms of global symptom improvement, patients receiving the combination oil treatment gave a median response of ‘much improved’ while those receiving placebo reported a result of ‘minimally improved.’

Interestingly, another study looking at enteric vs. non-enteric coated capsules revealed efficacy for both modes of product delivery into the body; however, the enteric-coated capsules offered a greater gastric and duodenal effect, likely because they dissolve farther along the GI tract.

While both caraway and peppermint oils have shown results when used separately, it is when using these two products in combination that better symptom resolution occurs. Although small, these studies show promising results for the use of a fixed combination of peppermint and caraway oils in the safe, long-term management of functional dyspepsia symptoms.


Irritable Bowel Syndrome

Another common functional disorder, irritable bowel syndrome (IBS), affects up to 20% of Canadians. As in functional dyspepsia, many IBS patients do not seek medical care. Symptoms express as abdominal pain, bloating, constipation, and diarrhea, or a combination of these. A literature review of clinical trials looking at enteric coated peppermint oil as a remedy for IBS showed an ‘overall success’ range of 58% (with a range from 39%-79%) for peppermint oil compared to placebo, at 29% (with a range from 10%-52%).

To provide an adequate comparison between studies, the researchers used the variable ‘overall success’ which indicated overall benefit, global improvement, or overall assessment, or similar parameters described in the original studies. When tested against three different smooth muscle relaxants, peppermint oil exhibited comparable results, suggesting equivalence of treatments, although the study authors do note that this evidence is preliminary. Participants described gastrointestinal side effects such as heartburn and perianal/anal burning or discomfort and reported these to be mild and transient.

A more recent study comparing enteric coated peppermint oil to placebo over a 4-week period demonstrated a 50% or greater reduction in IBS symptoms in 75% of the peppermint oil group compared with only 38% of individuals in the placebo group. Moreover, for more than 50% of patients taking the peppermint oil, the beneficial effects lasted for one month after therapy ceased.

First published in the Inside Tract® newsletter issue 165 – January/February 2008
Image Credist: ©, © Gastrointestinal Society