Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by abdominal pain, abdominal bloating, and altered bowel habits [1]. There are several pharmacological therapies for treating IBS, but none have been demonstrated to alter the natural history of IBS in the long term. In this regard, attention has been focused on controlling symptoms by inducing changes in intestinal bacteria. Drugs used for such purposes include prebiotics and probiotics. Probiotics are living bacteria known to be beneficial to human health, and prebiotics are ingredients in foods, such as fructooligosaccharides or inulin, that help the beneficial bacteria grow. The combination of prebiotics and probiotics is called synbiotics. According to a recently published systematic review [2], the amount of evidence for the therapeutic effect of IBS in these products has been inconsistent. Most evidence is limited to probiotics.

In the present issue, Lee et al. [3] investigated the dose-response effects of synbiotic supplementation on bowel symptoms and fatigue in patients with IBS. Thirty patients with IBS were randomly assigned to three group (high-dose of synbiotics, low-dose of synbiotics, and placebo) and received treatment for 8 weeks. The authors found no significant dose-dependent clinical effects of synbiotics in patients with IBS.

However, significant positive effects of high-dose synbiotics on gastrointestinal symptoms and fatigue were observed in patients with IBS. This study is meaningful because the authors investigated whether synbiotics exerted synergistic beneficial effects to help resolve fatigue in patients with IBS. However, additional evidence may be needed because of the small sample and effect sizes in this study.