Peppermint essential oil is one of the more common essential oils. It's plentiful and inexpensive, and the minty coolness it brings to our products is most welcome (except when we're soaking in it! Eek!) Peppermint essential oil is composed of 38% to 48% menthol (a monoterpene), 20% to 30% menthone, and about 6% 1,8-cineole (aka eucalyptol, which we discussed in the post on eucalyptus!)
Peppermint has been studied mainly for three things - the coolness it offers. its effects on the digestive system, its effect on respiration and cold symptoms, and its possible effect as an anesthetic for pain or itching. Let's take a look at digestion today!
There have been quite a number studies showing that mint, is great for digestion, but this doesn't really help us when we are studying the essential oil. We find different compounds in the leaves when we make a tea out of it - water soluble compounds like flavonoids - than we do in the essential oil, where we'd find oil soluble compounds like terpenes. (Click here for a bit more information.)
This study (2008) looked at the efficacy of peppermint oil on post operative nausea, and found it was more effective than placebo...but we have no idea of the size of this study, so we'll have to take those results with a grain of salt. Another study (Hills & Aaronson, 1991) found that peppermint essential oil has a "calcium blocking activity in gut tissue" that relaxes the lower sphincter and helps facilitate eructions (known to non-medical people as burps!) but it can aggravate reflux. This study also that concluded that "peppermint oil relaxes gastrointestinal smooth muscle by reducing calcium influx."
This study concluded that, "Peppermint oil and caraway oil show a relaxing effect on the gall-bladder and the former slows small intestinal transit...", and this study noted that, "...all other studies result in effects, indicating a substantial spasmolytic effect [muscle relaxing effect] of PO of the smooth muscles of the gastrointestinal tract." (Grigolet & Grigolet, 2004).
There have been quite a few studies on peppermint essential oil on irritable bowel syndrome. Here's a critical review and meta-analysis that concluded that "The role of peppermint oil in the symptomatic treatment of IBS has so far not been established beyond reasonable doubt. Well designed and carefully executed studies are needed to clarify the issue." And there was another analysis by Grigolet & Grigolet (2005) that found that enteric coated peppermint oil at 180 to 220 mg given thrice daily was an effective treatment. Is the jury out on peppermint's usage for irritable bowel syndrome? It appears it might be.
So it looks like peppermint oil is effective for stomach problems by making the muscles in our digestive tract relax. But this comes from ingesting peppermint - quite a few of the studies made use of time released peppermint oil capsules - not from inhaling it. This isn't to say there aren't some benefits to inhaling this wonderful essential oil, but it doesn't appear that relieving digestive issues are amongst them.
Join me tomorrow for more fun with peppermint oil as we take a look at peppermint's effects upon respiration and cold symptoms (which I need right now....sniff! sniff!)