Effect of Gum Chewing on Air Swallowing, Saliva Swallowing and Belching.

BACKGROUND Eructation is a physiologic event which allows gastric venting of swallowed air and most of the time is not perceived as a symptom. This is called gastric belching. Supragastric belching occurs when swallowed air does not reach the stomach and returns by mouth a short time after swallowing. This situation may cause discomfort, life limitations and problems in daily life. OBJECTIVE Our objective in this investigation was to evaluate if gum chewing increases the frequency of gastric and/or supragastric belches. METHODS Esophageal transit of liquid and gas was evaluated by impedance measurement in 16 patients with complaint of troublesome belching and in 15 controls. The Rome III criteria were used in the diagnosis of troublesome belching. The esophageal transit of liquid and gas was measured at 5 cm, 10 cm, 15 cm and 20 cm from the lower esophageal sphincter. The subjects were evaluated for 1 hour which was divided into three 20-minute periods: (1) while sitting for a 20-minute base period; (2) after the ingestion of yogurt (200 mL, 190 kcal), in which the subjects were evaluated while chewing or not chewing gum; (3) final 20-minute period in which the subjects then inverted the task of chewing or not chewing gum. In gastric belch, the air flowed from the stomach through the esophagus in oral direction and in supragastric belch the air entered the esophagus rapidly from proximal and was expulsed almost immediately in oral direction. Air swallows were characterized by an increase of at least 50% of basal impedance and saliva swallow by a decrease of at least 50% of basal impedance, that progress from proximal to distal esophagus. RESULTS In base period, air swallowing was more frequent in patients than in controls and saliva swallowing was more frequent in controls than in patients. There was no difference between the medians of controls and patients in the number of gastric belches and supragastric belches. In six patients, supragastric belches were seen at least once during the 20-minute base period. None of the controls had supragastric belches. In the control group, the ingestion of yogurt caused no significant alteration in the number of air swallows, saliva swallows, gastric belches and supragastric belches. In the patient group, there was an increase in the number of air swallows. If the subjects were chewing gum during this 20-minute period, there was an increase in the number of saliva swallows in both groups, without alterations of the number of air swallow, gastric belches and supragastric belches. There was no alteration in the number of the saliva swallows, air swallows, gastric belches and supragastric belches in both groups for subjects who did not chew gum in the 20-40 minute period after yogurt ingestion. When the subjects were chewing the gum, there was an increase in saliva swallows in the control and patients groups and in air swallows in the patients group. CONCLUSION Gum chewing causes an increase in saliva swallowing in both patients with excessive belching and in controls, and an increase in air swallowing in patients with excessive belching 20 minutes after yogurt ingestion. Gum chewing did not increase or decrease the frequency of gastric or supragastric belches.