Postoperative ileus (POI) is a transient impairment of gastrointestinal motility following abdominal surgery, which leads to increased morbidity, prolonged hospitalization and increased healthcare cost.  The pathogenesis of POI involves inflammation and oxidative stress, similar to ischemia/reperfusion injury, which can be counteracted with beetroot juice. Beetroot juice is a source of inorganic nitrate, which exerts its protective effect after conversion to nitrite in the body. We demonstrated in a preclinical model that administration of exogenous nitrite protects against POI. In addition, promising results were obtained after beetroot juice intake in a proof-of-concept study investigating recovery of gastrointestinal function after laparoscopic colorectal surgery. The aim of this multicenter double-blinded randomized phase II trial is to assess the protective effect of beetroot juice on POI following colorectal surgery.