OBJECTIVES: The lower esophageal sphincter (LES), surrounded by diaphragmatic muscle, prevents gastroesophageal reflux. When these structures become incompetent, gastric contents may cause gastroesophageal reflux disease (GERD). For treatment, lifestyle interventions are always recommended. We hypothesized that by actively training the crura of the diaphragm as part of the LES using breathing training exercises, GERD can be positively influenced.METHODS: A prospective randomized controlled study was performed. Patients with non-erosive GERD or healed esophagitis without large hernia and/or previous surgery were included. Patients were randomized and allocated either to active breathing training program or to a control group. Quality of life (QoL), pH-metry, and on-demand proton pump inhibitor (PPI) usage were assessed at baseline and after 4 weeks of training. For long-term follow-up, all patients were invited to continue active breathing training and were further assessed regarding QoL and PPI usage after 9 months. Paired and unpaired t-test was used for statistical analysis. RESULTS: Nineteen patients with non-erosive GERD or healed esophagitis were randomized into two groups (10 training group and 9 control group). There was no difference in baseline patient characteristics between the groups and all patients finished the study. There was a significant decrease in time with a pH < 4.0 in the training group (9.1±1.3 vs. 4.7±0.9%; P < 0.05), but there was no change in the control group. QoL scores improved significantly in the training group (13.4±1.98 before and 10.8±1.86 after training; P < 0.01), but no changes in QoL were seen in the control group. At longterm follow-up at 9 months, patients who continued breathing exercise (11/19) showed a significant decrease in QoL scores and PPI usage (15.1±2.2 vs. 9.7±1.6; 98±34 vs. 25±12 mg/week, respectively; P < 0.05), whereas patients who did not train had no long-term effect. CONCLUSIONS: We show that actively training the diaphragm by breathing exercise can improve GERD as assessed by pH-metry, QoL scores and PPI usage. This non-pharmacological lifestyle intervention could help to reduce the disease burden of GERD.