OBJECTIVES/HYPOTHESIS:To assess the impact of diet on the saliva pepsin concentration of patients with laryngopharyngeal reflux (LPR). STUDY DESIGN:Non-controlled Prospective Study. METHODS:Patients with positive LPR regarding hypopharyngeal-esophageal impedance-pH monitoring (HEMII-pH) were enrolled from three European Hospitals. Patients collected three saliva samples, respectively, in the morning (fasting), and 1 to 2 hour after lunch and dinner. Patients carefully detailed foods and beverages consumed during meals and before the pepsin samples. The 3-month treatment was based on the association of diet, proton pump inhibitors, alginate, or magaldrate regarding the HEMII-pH characteristics. Reflux Symptom Score (RSS) and Reflux Sign Assessment (RSA) were used for assessing the pre- to posttreatment clinical evolution. The Refluxogenic Diet Score and the Refluxogenic Score of a Dish (RESDI) were used to assess the refluxogenic potential of foods and beverages. The relationship between saliva pepsin concentration, HEMII-pH, RESDI, RSS, and RSA was investigated through multiple linear regression. RESULTS:Forty-two patients were included. The saliva pepsin concentration of the 24-hour period of testing was significantly associated with foods and beverages consumed during the testing period and the evening dinner (rs = 0.973, P < .001). RSS and RSA significantly improved throughout treatment. The level of saliva pepsin in the morning was a negative predictive factor of the therapeutic response regarding RSA and RSS (P < .036). CONCLUSIONS:Foods and beverages may significantly impact the saliva pepsin concentration of patients with LPR. Patients with high-level saliva pepsin in the morning had lower therapeutic response compared with those with low-level saliva pepsin. LEVEL OF EVIDENCE:4 Laryngoscope, 131:350-359, 2021.