Peppermint Essential Oil - History, Uses, and Benefits
Peppermint, a hybrid mint created by cross-breeding spearmint and water mint, is one of the most widely consumed herbs on the planet.  Europe and North America grow the majority of peppermint plants but just about every store on the planet sells some sort of peppermint-flavored or peppermint-scented product. 
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After harvest, most manufacturers dry the leaves and package them as a standalone tea or part of an herbal tea blend. The second most common preparation involves extracting the essential oils and either bottling them in liquid form or packaging them into capsules. The article focuses on the uses and benefits of peppermint oil.
Methone and menthol are the two key bioactive ingredients found in peppermint oil. The menthol content is responsible for the distinct odor, pungent taste, and cooling sensation after oral ingestion or topical application. 
Peppermint oil is also rich in rosmarinic acid, a potent phenol compound, as well as the flavonoids eriocitrin, luteolin, and hesperidin.  Phenols and flavonoids offer a number of health-promoting benefits as observed in human, animal, and cellular studies.
Peppermint Essential Oil Uses
The two most common uses of peppermint oil include oral ingestion and the incorporation of the oil into topical creams designed for direct application to the skin. Folk medicine recommends peppermint oil as an all-natural way to improve digestion, especially in those with irritable bowel syndrome (IBS).
IBS may be characterized by abdominal pain, bloating, gas, constipation, and/or diarrhea and affects between 5 and 20% of the population.  450 to 750mg or 0.1 to 0.2mL of peppermint oil, divided across two or three doses throughout the day, appears to be the sweet-spot for treating digestive issues.6 Peppermint oil may also be ingested to treat nausea, indigestion, cold symptoms, muscle and nerve pain, and general stomach problems. 
Peppermint oil relaxes the muscles of the stomach and intestines, expedites digestion in the stomach, and regulates the passing of food through the colon.  Manufacturers may also include peppermint oil in very small quantities to flavor foods.
A skin cream with peppermint oil offers aromatherapeutic and skin conditioning benefits as well as the potential to regrow hair when studied in animal models.  Those with tension headaches may also apply peppermint directly to the affected area to decrease the intensity, pain, and discomfort. 
A solution of 10% peppermint oil applied in a thin layer directly on the forehead when a headache begins, followed by two or three more applications during the headaches, appears to be most effective.  While peppermint oil is not the Holy Grail of supplements, it has a number of potential uses and applications based on scientific and anecdotal evidence.
Peppermint oil is well tolerated in most individuals when used in moderate doses. Do not consume this oil alongside iron supplements as it may inhibit full iron absorption.  Menthol is the main active ingredient in peppermint oil, but more menthol is not always better. Minor overconsumption can cause side effects like heartburn, anal/perianal burning, gastroesophageal reflux, vomiting, and diarrhea. 
Consuming a lower dose or enteric-coated peppermint oil capsules may decrease or complete alleviate some of these side effects. Minor over-application of a skin cream containing peppermint oil may cause inflammation, clinically classified as contact dermatitis. 
Major over-consumption may damage or destroy liver cells and kidney cells, potentially to the point of complete organ failure.  These warnings are not meant to dissuade you from trying peppermint oil but are meant to reiterate the importance of carefully dosing this potent oil.
Peppermint Oil Benefits
The majority of research on peppermint completed thus far examines its effects on digestion but there's a growing body of research on peppermint oil's positive effects on headaches, exercise, cognitive performance, and hair growth.
A meta-analysis of four studies and 392 patients found that peppermint oil is superior to placebo in treating IBS symptoms.  In one study 57 patients with IBS consumed either two enteric-coated capsules of peppermint oil or a placebo two times per day for four weeks and reported their frequency and intensity of IBS symptoms.
This included abdominal bloating, abdominal pain or discomfort, diarrhea, constipation, a feeling of incomplete evacuation, pain at defecation, the passage of gas or mucus and urgency at defecation.
At week four, 75% of the patients consuming peppermint oil capsules reported a reduction of over 50% of total IBS symptoms, significantly more than the placebo. Four weeks after peppermint oil treatment the same patients experienced a slight increase in total IBS symptoms but still reported 27% lower scores compared to baseline. 
Peppermint oil has positive effects on digestion and the overall gastrointestinal tract even after the regular oral consumption stops.
A study of 110 patients between the ages of 18 and 70 with IBS symptoms consumed one capsule, delivering 0.2mL of peppermint oil, before meals three or four times per day for one month. 79% of patients in the peppermint oil group experienced significant decreases in abdominal pain severity, many of reported the complete elimination of pain. Those consuming peppermint oil also reported significantly reduced abdominal distension, stool frequency, and flatulence. 
Two additional studies examining 164 patients found that daily consumption of peppermint oil three times per day for six to eight weeks significantly reduces the frequency and intensity of abdominal pain compared to placebo.  While the abdominal pain scores increased after treatment ended, these values were still below baseline and placebo group values. Enteric-coated peppermint oil appears to have the strongest positive effects on those with IBS.
Peppermint oil contains menthol and menthone, compounds with antifungal, antiviral, and antimicrobial properties. When applied to the skin, solutions with moderate amounts of peppermint oil can decrease skin itchiness, redness, irritation, and inflammation. 
Peppermint oil also provides significant relief when applied to the forehead at the onset of a tension headache. 41 patients between the ages of 18 and 65 experienced 164 headache attacks and found that a 10% peppermint oil solution applied directly to the forehead and temples at the 0, 15, 30 and minute-mark significantly decrease the pain intensity compared to ethanol placebo. 
A second study found that a combination of peppermint oil and ethanol significantly reduced headache pain while a combination of peppermint oil, eucalyptus oil, and ethanol significantly improved cognitive performance and mental relaxation.  While this study did not examine peppermint oil as a standalone ingredient, it works synergistically with eucalyptus oil and ethanol to improve physical and mental states when applied topically to the forehead.
The less-studied benefits of peppermint oil include its positive effects on cognitive function, exercise performance, and hair growth. Twelve male patients consumed 500mL of mineral water mixed with 0.05mL of peppermint oil daily for ten days and then performed treadmill-based exercise tests to measure performance.
The consumption of peppermint oil increased forced vital capacity by 4.8%, peak expiratory flow rate of 4.3%, and peak inspiratory flow by 15.2%.  These findings indicate subjects were able to take larger and more efficient breaths. The peppermint oil also significantly increased exercise time to exhaustion, overall work performed, power output, and V02. 
The increased oxygen consumption measured was one of the primary drivers for improved exercise performance. The inhalation of the peppermint oil aroma can increase performance on typing activities, attentional processes, virtual recognition memory, working memory, and visual-motor response. 
If you've ever taken a big huff of a peppermint-flavored candle or consumed food or chewing gum with peppermint oil then you may have also noticed this improved concentration and cognitive performance. A small study examining the topical application of a 3% peppermint oil solution for hair growth found that it significantly increased dermal thickness, follicle depth, and follicle number compared to saline placebo, jojoba oil, and a 3% minoxidil solution. 
Although this was not a study on humans the findings are promising for loss experiencing hair thinning or loss.
Tiger Fitness offers a handful of products containing peppermint oil. Many on-the-go energy bars use peppermint oil as a flavoring agent. One product uses peppermint oil as a topical aromatherapy ingredient. Some supplement retailers include peppermint oil as part of their pre-workout or multivitamin products.
- Nugo Dark Bars - uses peppermint extract to flavor the mint chocolate chip bar
- Twinlab Dualtabs - uses peppermint oil to improve the digestibility of this multivitamin
- Honey Stinger Bars - uses natural peppermint oil to flavor the dark chocolate mint almond bar
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