In their systematic review and meta-analysis, Khanna et al. evaluated data from 726 patients who took part in nine randomized placebo-controlled trials of peppermint oil capsules (taken for at least 2 weeks) for the treatment of IBS. Peppermint oil was significantly better than placebo for global improvement of symptoms and improvement in abdominal pain. Adverse events were more likely in the treatment group but were mild and transient.