Current Use and Scientific Evidence

    Today, spearmint is most commonly used as a breath freshener in gum, mouthwash, toothpaste, and after dinner mints. However, there has been increasing scientific evidence to support the traditional use of spearmint as a soothing remedy for gastrointestinal upset, as well as mixed evidence as a nasal decongestant (Kunnumakkara, 2009). 
    One of the most prevalent traditional uses for spearmint is to treat gastrointestinal upset, nausea, vomiting, and flatulence. In 2006, Vejdani et al investigated the effect of Mentha spicata in combination with Melissa officinalis and Coriandrum sativum (a combination known as Carmint) as a treatment for abdominal pain and bloating in patients with irritable bowel syndrome (IBS). After the 60 day trial, patients taking Carmint three times a day experienced a significant decrease in abdominal pain and bloating compared to the placebo group, both in respect to number of days with discomfort and severity of discomfort experienced (Vejdani, 2006).
    The study by Vejdani et al (2006) shows a promising role for Carmint in the management of IBS symptoms.  Their protocol was well thought out, and their choice of using essential oils rather than tea made it possible for this study to be double blind placebo controlled, which strengthens their findings significantly.  All results were supported with statistical significance (Vejdani, 2006). Though their study did not investigate differences in efficacy for specific subtypes of IBS, it is a strongly supported pilot project that should be followed up with a more subtype specific, larger trial.
    A second popular traditional use of spearmint is the use of its active compound, menthol, in the treatment of respiratory distress caused by nasal congestion. In 2008, Kenia, Houghton and Beardsmore investigated the effect of inhaled methol on nasal air flow and volume (measured by a spirometer) and perception of nasal patency, as well as the number of coughs in response to inhaled citric acid. No significant relationship was found between objective nasal air flow or cough frequency and methol inhalation. However, there was a significant increase in subjective perception of nasal patency for the methol condition compared with placebo. The authors suggest that this discrepancy between objective and subjective measures may be due to the cooling effect of menthol increasing the perception of greater airflow.
    This study had several crucial limitations that effect its generalizability. Firstly, the participants were all healthy children, and respiratory conditions were an exclusion factor even though the use of spearmint to aid with respiratory distress is only traditionally used in patients with a cough, cold, flu or mild asthma (Kunnumakkara, 2009). Secondly, though it was a placebo controlled trial it was only single blind, with no indication for why they chose this protocol. This may be a source of bias explaining the discrepancy between objective and subjective results.