1- Carminative effect
Carminative effect of mint and mint oil is entirely known. Although its exact mechanism of action has not been determined, one proposed mechanism is relaxation of lower esophageal sphincter leading to reduction of stomach gas pressure.(1) In other words, mint oil causes relaxation of the lower esophageal sphincter and equalization of intra-gastric and intra-esophageal pressures.
In a placebo-controlled, randomized, double blind clinical trial, 70 patients with marked chronic digestive problems such as flatulence or bloating were treated with an herbal tablet containing mint for a period of 14 days. Analysis of the results clearly showed that the patients who were administered mint tablets had substantially lower complaints than patients who were given placebo (P<0.05). The results of ultrasound for the amount of gas inside the stomach were also indicative of the effectiveness of mint tablet (P<0.05).
2- Anti-spasmodic effect
Anti-spasmodic effects of mint extract have been well documented. Researchers have concluded that the ability of mint oil to inhibit contractions of isolated smooth muscles is via blockage of the influx of calcium into the muscle cells and clinical effectiveness of mint oil in treatment of irritable bowel syndrome is a result of inhibition of hyper-contractility of intestinal smooth muscle, thereby returning the muscle to its proper tone.
3- Treatment of dyspepsia
In a randomized, double blind clinical trial on the treatment of dyspepsia, mint oil in combination with herbs such as caraway and fennel was found to be superior to the spasmolytic drug metoclopramide in terms of relief of symptoms such as pain, nausea, belching and heartburn (P=0.02).
4- Inhibition of H. Pylori proliferation
Based to studies, spearmint oil and its constituents can inhibit the proliferation of susceptible and resistant strains of H. Pylori and Staphylococcus aureus.(4) Regarding the role of H.pylori in gastric and duodenal inflammation and ulcer, inhibition of this bacteria is important.