Enrolled patients will undergo 24h gastric pH monitoring and subsequently (if gastric pH drops below pH 4 during 24h monitoring) will be randomized to receive placebo (40 mg QD) or esomeprazole (40 mg QD) for 16 weeks of therapy. 24h gastric pH monitoring will be repeated 2nd and 3rd time in all participating patients at the end of 4th and 8th weeks of therapy. Additionally, in all participants NUD symptoms will be re-assessed at the end of 4th, 8th, 12th and 16th weeks of therapy.